GDB Internals Guide

gdb Internals
A guide to the internals of the GNU debugger
John Gilmore
Cygnus Solutions
Second Edition:
Stan Shebs
Cygnus Solutions
Cygnus Solutions
Revision
TEXinfo 2004-02-19.09
c 1990,1991,1992,1993,1994,1996,1998,1999,2000,2001, 2002, 2003, 2004, 2005,
Copyright 2006 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the terms of
the GNU Free Documentation License, Version 1.1 or any later version published by the
Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with
no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free
Documentation License”.
i
Table of Contents
Scope of this Document . . . . . . . . . . . . . . . . . . . . . . . 1
1
Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2
Overall Structure . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.1
2.2
2.3
3
The Symbol Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
The Target Side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Prologue Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Breakpoint Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Single Stepping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Signal Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Thread Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Inferior Function Calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Longjmp Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Watchpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.9.1 x86 Watchpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.10 Checkpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.11 Observing changes in gdb internals . . . . . . . . . . . . . . . . . . . . . . . . . 12
4
User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1
4.2
Command Interpreter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UI-Independent Output—the ui_out Functions . . . . . . . . . . . . . . .
4.2.1 Overview and Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.2 General Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.3 Table, Tuple and List Functions . . . . . . . . . . . . . . . . . . . . . . . .
4.2.4 Item Output Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.5 Utility Output Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.6 Examples of Use of ui_out functions . . . . . . . . . . . . . . . . . . . .
4.3 Console Printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4 TUI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
12
13
13
14
14
16
17
18
21
21
libgdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1 libgdb 1.0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 libgdb 2.0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3 The libgdb Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4 CLI support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5 libgdb components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
22
22
22
23
ii
6
Symbol Handling . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1
6.2
6.3
Symbol Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Partial Symbol Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fundamental Types (e.g., FT_VOID, FT_BOOLEAN). . . . . . . . . . . . . . . .
Type Codes (e.g., TYPE_CODE_PTR, TYPE_CODE_ARRAY). . . . . . . . . . .
Builtin Types (e.g., builtin_type_void, builtin_type_char). . .
6.4 Object File Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.1 a.out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.2 COFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.3 ECOFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.4 XCOFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.5 PE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.6 ELF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.7 SOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.8 Other File Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5 Debugging File Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.1 stabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.2 COFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.3 Mips debug (Third Eye) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.4 DWARF 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.5 DWARF 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.6 SOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.6 Adding a New Symbol Reader to gdb . . . . . . . . . . . . . . . . . . . . . . .
6.7 Memory Management for Symbol Files . . . . . . . . . . . . . . . . . . . . . . .
7
Language Support . . . . . . . . . . . . . . . . . . . . . . . . 29
7.1
8
Adding a Source Language to gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Host Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1
8.2
9
23
24
26
26
26
26
26
26
26
27
27
27
27
27
27
27
27
28
28
28
28
28
28
28
Adding a New Host . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Host Conditionals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Target Architecture Definition . . . . . . . . . . . . . 34
9.1 Operating System ABI Variant Handling . . . . . . . . . . . . . . . . . . . . .
9.2 Registers and Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.3 Pointers Are Not Always Addresses . . . . . . . . . . . . . . . . . . . . . . . . . .
9.4 Address Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.5 Raw and Virtual Register Representations. . . . . . . . . . . . . . . . . . . .
9.6 Using Different Register and Memory Data Representations . . .
9.7 Frame Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.8 Inferior Call Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.9 Compiler Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.10 Target Conditionals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.11 Adding a New Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.12 Converting an existing Target Architecture to Multi-arch . . . . .
9.12.1 Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
36
36
38
39
40
41
42
42
42
57
58
58
iii
9.12.2
9.12.3
9.12.4
9.12.5
9.12.6
9.12.7
9.12.8
10
File Targets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standard Protocol and Remote Stubs . . . . . . . . . . . . . . . . . . . . . . .
ROM Monitor Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Custom Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transport Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Builtin Simulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Native core file Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ptrace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
/proc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
win32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
shared libraries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Native Conditionals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
62
62
63
63
63
63
Support Libraries . . . . . . . . . . . . . . . . . . . . . . . . 65
12.1 BFD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2 opcodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3 readline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4 mmalloc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5 libiberty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5.1 obstacks in gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6 gnu-regex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.7 include . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
60
60
60
61
61
61
Native Debugging . . . . . . . . . . . . . . . . . . . . . . . 61
11.1
11.2
11.3
11.4
11.5
11.6
12
58
59
59
59
59
60
60
Target Vector Definition . . . . . . . . . . . . . . . . . 60
10.1
10.2
10.3
10.4
10.5
10.6
11
Add the multi-arch initialization code . . . . . . . . . . . . . . . . . .
Update multi-arch incompatible mechanisms . . . . . . . . . . . .
Prepare for multi-arch level to one . . . . . . . . . . . . . . . . . . . . .
Set multi-arch level one . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Convert remaining macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Set multi-arch level to two. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Delete the TM file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
65
65
65
65
66
66
66
67
Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
13.1 Cleanups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2 Per-architecture module data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3 Wrapping Output Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4 gdb Coding Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.1 ISO C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.2 Memory Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.3 Compiler Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.4 Formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.5 Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.6 C Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.7 Function Prototypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.8 Internal Error Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
67
68
70
70
70
70
71
72
72
73
73
73
iv
13.4.9 File Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
13.4.10 Include Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
13.4.11 Clean Design and Portable Implementation . . . . . . . . . . . . 74
14
Porting gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
15
Versions and Branches . . . . . . . . . . . . . . . . . . . 77
15.1 Versions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.2 Release Branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3 Vendor Branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.4 Experimental Branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.4.1 Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.4.2 Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
77
78
78
79
79
79
16
Start of New Year Procedure . . . . . . . . . . . . . 80
17
Releasing gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
17.1 Branch Commit Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2 Obsoleting code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3 Before the Branch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.1 Review the bug data base . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.2 Check all cross targets build . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.4 Cut the Branch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.5 Stabilize the branch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6 Create a Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6.1 Create a release candidate . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6.2 Sanity check the tar ball . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6.3 Make a release candidate available . . . . . . . . . . . . . . . . . . . . .
17.6.4 Make a formal release available . . . . . . . . . . . . . . . . . . . . . . . .
17.6.5 Cleanup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7 Post release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
Testsuite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
18.1
18.2
18.3
19
80
81
81
82
82
82
83
84
84
86
87
87
88
89
Using the Testsuite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Testsuite Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Writing Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
19.1
19.2
19.3
19.4
Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Debugging gdb with itself . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Submitting Patches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Obsolete Conditionals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
92
93
93
94
v
Appendix A gdb Currently available observers
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
A.1 Implementation rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
A.2 Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
A.3 normal_stop Notifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Appendix B GNU Free Documentation License
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
B.1
ADDENDUM: How to use this License for your documents . . 103
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Chapter 2: Overall Structure
1
Scope of this Document
This document documents the internals of the GNU debugger, gdb. It includes description
of gdb’s key algorithms and operations, as well as the mechanisms that adapt gdb to
specific hosts and targets.
1 Requirements
Before diving into the internals, you should understand the formal requirements and other
expectations for gdb. Although some of these may seem obvious, there have been proposals
for gdb that have run counter to these requirements.
First of all, gdb is a debugger. It’s not designed to be a front panel for embedded
systems. It’s not a text editor. It’s not a shell. It’s not a programming environment.
gdb is an interactive tool. Although a batch mode is available, gdb’s primary role is to
interact with a human programmer.
gdb should be responsive to the user. A programmer hot on the trail of a nasty bug, and
operating under a looming deadline, is going to be very impatient of everything, including
the response time to debugger commands.
gdb should be relatively permissive, such as for expressions. While the compiler should
be picky (or have the option to be made picky), since source code lives for a long time
usually, the programmer doing debugging shouldn’t be spending time figuring out to mollify
the debugger.
gdb will be called upon to deal with really large programs. Executable sizes of 50 to 100
megabytes occur regularly, and we’ve heard reports of programs approaching 1 gigabyte in
size.
gdb should be able to run everywhere. No other debugger is available for even half as
many configurations as gdb supports.
2 Overall Structure
gdb consists of three major subsystems: user interface, symbol handling (the symbol side),
and target system handling (the target side).
The user interface consists of several actual interfaces, plus supporting code.
The symbol side consists of object file readers, debugging info interpreters, symbol table
management, source language expression parsing, type and value printing.
The target side consists of execution control, stack frame analysis, and physical target
manipulation.
The target side/symbol side division is not formal, and there are a number of exceptions. For instance, core file support involves symbolic elements (the basic core file reader
is in BFD) and target elements (it supplies the contents of memory and the values of registers). Instead, this division is useful for understanding how the minor subsystems should
fit together.
Chapter 3: Algorithms
2
2.1 The Symbol Side
The symbolic side of gdb can be thought of as “everything you can do in gdb without
having a live program running”. For instance, you can look at the types of variables, and
evaluate many kinds of expressions.
2.2 The Target Side
The target side of gdb is the “bits and bytes manipulator”. Although it may make reference
to symbolic info here and there, most of the target side will run with only a stripped
executable available—or even no executable at all, in remote debugging cases.
Operations such as disassembly, stack frame crawls, and register display, are able to work
with no symbolic info at all. In some cases, such as disassembly, gdb will use symbolic info
to present addresses relative to symbols rather than as raw numbers, but it will work either
way.
2.3 Configurations
Host refers to attributes of the system where gdb runs. Target refers to the system where
the program being debugged executes. In most cases they are the same machine, in which
case a third type of Native attributes come into play.
Defines and include files needed to build on the host are host support. Examples are tty
support, system defined types, host byte order, host float format.
Defines and information needed to handle the target format are target dependent. Examples are the stack frame format, instruction set, breakpoint instruction, registers, and
how to set up and tear down the stack to call a function.
Information that is only needed when the host and target are the same, is native dependent. One example is Unix child process support; if the host and target are not the same,
doing a fork to start the target process is a bad idea. The various macros needed for finding
the registers in the upage, running ptrace, and such are all in the native-dependent files.
Another example of native-dependent code is support for features that are really part
of the target environment, but which require #include files that are only available on the
host system. Core file handling and setjmp handling are two common cases.
When you want to make gdb work “native” on a particular machine, you have to include
all three kinds of information.
3 Algorithms
gdb uses a number of debugging-specific algorithms. They are often not very complicated,
but get lost in the thicket of special cases and real-world issues. This chapter describes the
basic algorithms and mentions some of the specific target definitions that they use.
3.1 Frames
A frame is a construct that gdb uses to keep track of calling and called functions.
gdb’s frame model, a fresh design, was implemented with the need to support dwarf’s
Call Frame Information in mind. In fact, the term “unwind” is taken directly from that
Chapter 3: Algorithms
3
specification. Developers wishing to learn more about unwinders, are encouraged to read
the the dwarf specification.
gdb’s model is that you find a frame’s registers by “unwinding” them from the next
younger frame. That is, ‘get_frame_register’ which returns the value of a register in frame
#1 (the next-to-youngest frame), is implemented by calling frame #0’s frame_register_
unwind (the youngest frame). But then the obvious question is: how do you access the
registers of the youngest frame itself?
To answer this question, GDB has the sentinel frame, the “-1st” frame. Unwinding
registers from the sentinel frame gives you the current values of the youngest real frame’s
registers. If f is a sentinel frame, then get_frame_type (f ) == SENTINEL_FRAME.
3.2 Prologue Analysis
To produce a backtrace and allow the user to manipulate older frames’ variables and arguments, gdb needs to find the base addresses of older frames, and discover where those
frames’ registers have been saved. Since a frame’s “callee-saves” registers get saved by
younger frames if and when they’re reused, a frame’s registers may be scattered unpredictably across younger frames. This means that changing the value of a register-allocated
variable in an older frame may actually entail writing to a save slot in some younger frame.
Modern versions of GCC emit Dwarf call frame information (“CFI”), which describes
how to find frame base addresses and saved registers. But CFI is not always available, so
as a fallback gdb uses a technique called prologue analysis to find frame sizes and saved
registers. A prologue analyzer disassembles the function’s machine code starting from its
entry point, and looks for instructions that allocate frame space, save the stack pointer in a
frame pointer register, save registers, and so on. Obviously, this can’t be done accurately in
general, but it’s tractible to do well enough to be very helpful. Prologue analysis predates
the GNU toolchain’s support for CFI; at one time, prologue analysis was the only mechanism
gdb used for stack unwinding at all, when the function calling conventions didn’t specify a
fixed frame layout.
In the olden days, function prologues were generated by hand-written, target-specific
code in GCC, and treated as opaque and untouchable by optimizers. Looking at this code,
it was usually straightforward to write a prologue analyzer for gdb that would accurately
understand all the prologues GCC would generate. However, over time GCC became more
aggressive about instruction scheduling, and began to understand more about the semantics
of the prologue instructions themselves; in response, gdb’s analyzers became more complex
and fragile. Keeping the prologue analyzers working as GCC (and the instruction sets
themselves) evolved became a substantial task.
To try to address this problem, the code in ‘prologue-value.h’ and ‘prologue-value.c’
provides a general framework for writing prologue analyzers that are simpler and more robust than ad-hoc analyzers. When we analyze a prologue using the prologue-value framework, we’re really doing “abstract interpretation” or “pseudo-evaluation”: running the
function’s code in simulation, but using conservative approximations of the values registers
and memory would hold when the code actually runs. For example, if our function starts
with the instruction:
addi r1, 42
# add 42 to r1
Chapter 3: Algorithms
4
we don’t know exactly what value will be in r1 after executing this instruction, but we do
know it’ll be 42 greater than its original value.
If we then see an instruction like:
addi r1, 22
# add 22 to r1
we still don’t know what r1’s value is, but again, we can say it is now 64 greater than its
original value.
If the next instruction were:
mov r2, r1
# set r2 to r1’s value
then we can say that r2’s value is now the original value of r1 plus 64.
It’s common for prologues to save registers on the stack, so we’ll need to track the values
of stack frame slots, as well as the registers. So after an instruction like this:
mov (fp+4), r2
then we’d know that the stack slot four bytes above the frame pointer holds the original
value of r1 plus 64.
And so on.
Of course, this can only go so far before it gets unreasonable. If we wanted to be able
to say anything about the value of r1 after the instruction:
xor r1, r3
# exclusive-or r1 and r3, place result in r1
then things would get pretty complex. But remember, we’re just doing a conservative
approximation; if exclusive-or instructions aren’t relevant to prologues, we can just say
r1’s value is now “unknown”. We can ignore things that are too complex, if that loss of
information is acceptable for our application.
So when we say “conservative approximation” here, what we mean is an approximation
that is either accurate, or marked “unknown”, but never inaccurate.
Using this framework, a prologue analyzer is simply an interpreter for machine code,
but one that uses conservative approximations for the contents of registers and memory
instead of actual values. Starting from the function’s entry point, you simulate instructions
up to the current PC, or an instruction that you don’t know how to simulate. Now you can
examine the state of the registers and stack slots you’ve kept track of.
• To see how large your stack frame is, just check the value of the stack pointer register;
if it’s the original value of the SP minus a constant, then that constant is the stack
frame’s size. If the SP’s value has been marked as “unknown”, then that means the
prologue has done something too complex for us to track, and we don’t know the frame
size.
• To see where we’ve saved the previous frame’s registers, we just search the values we’ve
tracked — stack slots, usually, but registers, too, if you want — for something equal
to the register’s original value. If the calling conventions suggest a standard place to
save a given register, then we can check there first, but really, anything that will get
us back the original value will probably work.
This does take some work. But prologue analyzers aren’t quick-and-simple pattern
patching to recognize a few fixed prologue forms any more; they’re big, hairy functions.
Along with inferior function calls, prologue analysis accounts for a substantial portion of
Chapter 3: Algorithms
5
the time needed to stabilize a gdb port. So it’s worthwhile to look for an approach that
will be easier to understand and maintain. In the approach described above:
• It’s easier to see that the analyzer is correct: you just see whether the analyzer properly
(albiet conservatively) simulates the effect of each instruction.
• It’s easier to extend the analyzer: you can add support for new instructions, and know
that you haven’t broken anything that wasn’t already broken before.
• It’s orthogonal: to gather new information, you don’t need to complicate the code for
each instruction. As long as your domain of conservative values is already detailed
enough to tell you what you need, then all the existing instruction simulations are
already gathering the right data for you.
The file ‘prologue-value.h’ contains detailed comments explaining the framework and
how to use it.
3.3 Breakpoint Handling
In general, a breakpoint is a user-designated location in the program where the user wants
to regain control if program execution ever reaches that location.
There are two main ways to implement breakpoints; either as “hardware” breakpoints
or as “software” breakpoints.
Hardware breakpoints are sometimes available as a builtin debugging features with some
chips. Typically these work by having dedicated register into which the breakpoint address
may be stored. If the PC (shorthand for program counter) ever matches a value in a
breakpoint registers, the CPU raises an exception and reports it to gdb.
Another possibility is when an emulator is in use; many emulators include circuitry that
watches the address lines coming out from the processor, and force it to stop if the address
matches a breakpoint’s address.
A third possibility is that the target already has the ability to do breakpoints somehow;
for instance, a ROM monitor may do its own software breakpoints. So although these are
not literally “hardware breakpoints”, from gdb’s point of view they work the same; gdb
need not do anything more than set the breakpoint and wait for something to happen.
Since they depend on hardware resources, hardware breakpoints may be limited in number; when the user asks for more, gdb will start trying to set software breakpoints. (On
some architectures, notably the 32-bit x86 platforms, gdb cannot always know whether
there’s enough hardware resources to insert all the hardware breakpoints and watchpoints.
On those platforms, gdb prints an error message only when the program being debugged
is continued.)
Software breakpoints require gdb to do somewhat more work. The basic theory is that
gdb will replace a program instruction with a trap, illegal divide, or some other instruction
that will cause an exception, and then when it’s encountered, gdb will take the exception
and stop the program. When the user says to continue, gdb will restore the original
instruction, single-step, re-insert the trap, and continue on.
Since it literally overwrites the program being tested, the program area must be writable,
so this technique won’t work on programs in ROM. It can also distort the behavior of
programs that examine themselves, although such a situation would be highly unusual.
Chapter 3: Algorithms
6
Also, the software breakpoint instruction should be the smallest size of instruction, so
it doesn’t overwrite an instruction that might be a jump target, and cause disaster when
the program jumps into the middle of the breakpoint instruction. (Strictly speaking, the
breakpoint must be no larger than the smallest interval between instructions that may be
jump targets; perhaps there is an architecture where only even-numbered instructions may
jumped to.) Note that it’s possible for an instruction set not to have any instructions usable
for a software breakpoint, although in practice only the ARC has failed to define such an
instruction.
The basic definition of the software breakpoint is the macro BREAKPOINT.
Basic breakpoint object handling is in ‘breakpoint.c’. However, much of the interesting
breakpoint action is in ‘infrun.c’.
target_remove_breakpoint (bp_tgt )
target_insert_breakpoint (bp_tgt )
Insert or remove a software breakpoint at address bp_tgt ->placed_address.
Returns zero for success, non-zero for failure. On input, bp tgt contains the
address of the breakpoint, and is otherwise initialized to zero. The fields of the
struct bp_target_info pointed to by bp tgt are updated to contain other
information about the breakpoint on output. The field placed_address may
be updated if the breakpoint was placed at a related address; the field shadow_
contents contains the real contents of the bytes where the breakpoint has
been inserted, if reading memory would return the breakpoint instead of the
underlying memory; the field shadow_len is the length of memory cached in
shadow_contents, if any; and the field placed_size is optionally set and used
by the target, if it could differ from shadow_len.
For example, the remote target ‘Z0’ packet does not require shadowing memory,
so shadow_len is left at zero. However, the length reported by BREAKPOINT_
FROM_PC is cached in placed_size, so that a matching ‘z0’ packet can be used
to remove the breakpoint.
target_remove_hw_breakpoint (bp_tgt )
target_insert_hw_breakpoint (bp_tgt )
Insert or remove a hardware-assisted breakpoint at address bp_tgt ->placed_
address. Returns zero for success, non-zero for failure. See target_insert_
breakpoint for a description of the struct bp_target_info pointed to by
bp tgt; the shadow_contents and shadow_len members are not used for hardware breakpoints, but placed_size may be.
3.4 Single Stepping
3.5 Signal Handling
3.6 Thread Handling
3.7 Inferior Function Calls
Chapter 3: Algorithms
7
3.8 Longjmp Support
gdb has support for figuring out that the target is doing a longjmp and for stopping at
the target of the jump, if we are stepping. This is done with a few specialized internal
breakpoints, which are visible in the output of the ‘maint info breakpoint’ command.
To make this work, you need to define a macro called GET_LONGJMP_TARGET, which will
examine the jmp_buf structure and extract the longjmp target address. Since jmp_buf is
target specific, you will need to define it in the appropriate ‘tm-target.h’ file. Look in
‘tm-sun4os4.h’ and ‘sparc-tdep.c’ for examples of how to do this.
3.9 Watchpoints
Watchpoints are a special kind of breakpoints (see Chapter 3 [Algorithms], page 2) which
break when data is accessed rather than when some instruction is executed. When you have
data which changes without your knowing what code does that, watchpoints are the silver
bullet to hunt down and kill such bugs.
Watchpoints can be either hardware-assisted or not; the latter type is known as “software
watchpoints.” gdb always uses hardware-assisted watchpoints if they are available, and falls
back on software watchpoints otherwise. Typical situations where gdb will use software
watchpoints are:
• The watched memory region is too large for the underlying hardware watchpoint support. For example, each x86 debug register can watch up to 4 bytes of memory, so
trying to watch data structures whose size is more than 16 bytes will cause gdb to use
software watchpoints.
• The value of the expression to be watched depends on data held in registers (as opposed
to memory).
• Too many different watchpoints requested. (On some architectures, this situation is
impossible to detect until the debugged program is resumed.) Note that x86 debug
registers are used both for hardware breakpoints and for watchpoints, so setting too
many hardware breakpoints might cause watchpoint insertion to fail.
• No hardware-assisted watchpoints provided by the target implementation.
Software watchpoints are very slow, since gdb needs to single-step the program being
debugged and test the value of the watched expression(s) after each instruction. The rest
of this section is mostly irrelevant for software watchpoints.
When the inferior stops, gdb tries to establish, among other possible reasons, whether it
stopped due to a watchpoint being hit. For a data-write watchpoint, it does so by evaluating,
for each watchpoint, the expression whose value is being watched, and testing whether the
watched value has changed. For data-read and data-access watchpoints, gdb needs the
target to supply a primitive that returns the address of the data that was accessed or read
(see the description of target_stopped_data_address below): if this primitive returns a
valid address, gdb infers that a watchpoint triggered if it watches an expression whose
evaluation uses that address.
gdb uses several macros and primitives to support hardware watchpoints:
TARGET_HAS_HARDWARE_WATCHPOINTS
If defined, the target supports hardware watchpoints.
Chapter 3: Algorithms
8
TARGET_CAN_USE_HARDWARE_WATCHPOINT (type, count, other )
Return the number of hardware watchpoints of type type that are possible to
be set. The value is positive if count watchpoints of this type can be set, zero
if setting watchpoints of this type is not supported, and negative if count is
more than the maximum number of watchpoints of type type that can be set.
other is non-zero if other types of watchpoints are currently enabled (there are
architectures which cannot set watchpoints of different types at the same time).
TARGET_REGION_OK_FOR_HW_WATCHPOINT (addr, len )
Return non-zero if hardware watchpoints can be used to watch a region whose
address is addr and whose length in bytes is len.
target_insert_watchpoint (addr, len, type )
target_remove_watchpoint (addr, len, type )
Insert or remove a hardware watchpoint starting at addr, for len bytes. type
is the watchpoint type, one of the possible values of the enumerated data type
target_hw_bp_type, defined by ‘breakpoint.h’ as follows:
enum target_hw_bp_type
{
hw_write
= 0, /*
hw_read
= 1, /*
hw_access = 2, /*
hw_execute = 3 /*
};
Common (write) HW watchpoint */
Read
HW watchpoint */
Access (read or write) HW watchpoint */
Execute HW breakpoint */
These two macros should return 0 for success, non-zero for failure.
target_stopped_data_address (addr_p )
If the inferior has some watchpoint that triggered, place the address associated
with the watchpoint at the location pointed to by addr p and return non-zero.
Otherwise, return zero. Note that this primitive is used by gdb only on targets
that support data-read or data-access type watchpoints, so targets that have
support only for data-write watchpoints need not implement these primitives.
HAVE_STEPPABLE_WATCHPOINT
If defined to a non-zero value, it is not necessary to disable a watchpoint to
step over it.
HAVE_NONSTEPPABLE_WATCHPOINT
If defined to a non-zero value, gdb should disable a watchpoint to step the
inferior over it.
HAVE_CONTINUABLE_WATCHPOINT
If defined to a non-zero value, it is possible to continue the inferior after a
watchpoint has been hit.
CANNOT_STEP_HW_WATCHPOINTS
If this is defined to a non-zero value, gdb will remove all watchpoints before
stepping the inferior.
STOPPED_BY_WATCHPOINT (wait_status )
Return non-zero if stopped by a watchpoint. wait status is of the type struct
target_waitstatus, defined by ‘target.h’. Normally, this macro is defined to
Chapter 3: Algorithms
9
invoke the function pointed to by the to_stopped_by_watchpoint member of
the structure (of the type target_ops, defined on ‘target.h’) that describes the
target-specific operations; to_stopped_by_watchpoint ignores the wait status
argument.
gdb does not require the non-zero value returned by STOPPED_BY_WATCHPOINT
to be 100% correct, so if a target cannot determine for sure whether the inferior
stopped due to a watchpoint, it could return non-zero “just in case”.
3.9.1 x86 Watchpoints
The 32-bit Intel x86 (a.k.a. ia32) processors feature special debug registers designed to
facilitate debugging. gdb provides a generic library of functions that x86-based ports
can use to implement support for watchpoints and hardware-assisted breakpoints. This
subsection documents the x86 watchpoint facilities in gdb.
To use the generic x86 watchpoint support, a port should do the following:
• Define the macro I386_USE_GENERIC_WATCHPOINTS somewhere in the target-dependent
headers.
• Include the ‘config/i386/nm-i386.h’ header file after defining I386_USE_GENERIC_
WATCHPOINTS.
• Add ‘i386-nat.o’ to the value of the Make variable NATDEPFILES (see Chapter 11 [Native Debugging], page 61) or TDEPFILES (see Chapter 9 [Target Architecture Definition],
page 34).
• Provide implementations for the I386_DR_LOW_* macros described below. Typically,
each macro should call a target-specific function which does the real work.
The x86 watchpoint support works by maintaining mirror images of the debug registers.
Values are copied between the mirror images and the real debug registers via a set of macros
which each target needs to provide:
I386_DR_LOW_SET_CONTROL (val )
Set the Debug Control (DR7) register to the value val.
I386_DR_LOW_SET_ADDR (idx, addr )
Put the address addr into the debug register number idx.
I386_DR_LOW_RESET_ADDR (idx )
Reset (i.e. zero out) the address stored in the debug register number idx.
I386_DR_LOW_GET_STATUS
Return the value of the Debug Status (DR6) register. This value is used immediately after it is returned by I386_DR_LOW_GET_STATUS, so as to support
per-thread status register values.
For each one of the 4 debug registers (whose indices are from 0 to 3) that store addresses,
a reference count is maintained by gdb, to allow sharing of debug registers by several
watchpoints. This allows users to define several watchpoints that watch the same expression,
but with different conditions and/or commands, without wasting debug registers which are
in short supply. gdb maintains the reference counts internally, targets don’t have to do
anything to use this feature.
Chapter 3: Algorithms
10
The x86 debug registers can each watch a region that is 1, 2, or 4 bytes long. The ia32
architecture requires that each watched region be appropriately aligned: 2-byte region on
2-byte boundary, 4-byte region on 4-byte boundary. However, the x86 watchpoint support
in gdb can watch unaligned regions and regions larger than 4 bytes (up to 16 bytes) by
allocating several debug registers to watch a single region. This allocation of several registers
per a watched region is also done automatically without target code intervention.
The generic x86 watchpoint support provides the following API for the gdb’s application
code:
i386_region_ok_for_watchpoint (addr, len )
The macro TARGET_REGION_OK_FOR_HW_WATCHPOINT is set to call this function.
It counts the number of debug registers required to watch a given region, and
returns a non-zero value if that number is less than 4, the number of debug
registers available to x86 processors.
i386_stopped_data_address (addr_p )
The target function target_stopped_data_address is set to call this function.
This function examines the breakpoint condition bits in the DR6 Debug Status
register, as returned by the I386_DR_LOW_GET_STATUS macro, and returns the
address associated with the first bit that is set in DR6.
i386_stopped_by_watchpoint (void)
The macro STOPPED_BY_WATCHPOINT is set to call this function. The argument passed to STOPPED_BY_WATCHPOINT is ignored. This function examines
the breakpoint condition bits in the DR6 Debug Status register, as returned
by the I386_DR_LOW_GET_STATUS macro, and returns true if any bit is set.
Otherwise, false is returned.
i386_insert_watchpoint (addr, len, type )
i386_remove_watchpoint (addr, len, type )
Insert or remove a watchpoint. The macros target_insert_watchpoint and
target_remove_watchpoint are set to call these functions. i386_insert_
watchpoint first looks for a debug register which is already set to watch the
same region for the same access types; if found, it just increments the reference
count of that debug register, thus implementing debug register sharing between
watchpoints. If no such register is found, the function looks for a vacant debug register, sets its mirrored value to addr, sets the mirrored value of DR7
Debug Control register as appropriate for the len and type parameters, and
then passes the new values of the debug register and DR7 to the inferior by
calling I386_DR_LOW_SET_ADDR and I386_DR_LOW_SET_CONTROL. If more than
one debug register is required to cover the given region, the above process is
repeated for each debug register.
i386_remove_watchpoint does the opposite: it resets the address in the mirrored value of the debug register and its read/write and length bits in the
mirrored value of DR7, then passes these new values to the inferior via I386_
DR_LOW_RESET_ADDR and I386_DR_LOW_SET_CONTROL. If a register is shared by
several watchpoints, each time a i386_remove_watchpoint is called, it decrements the reference count, and only calls I386_DR_LOW_RESET_ADDR and I386_
DR_LOW_SET_CONTROL when the count goes to zero.
Chapter 3: Algorithms
11
i386_insert_hw_breakpoint (bp_tgt )
i386_remove_hw_breakpoint (bp_tgt )
These functions insert and remove hardware-assisted breakpoints. The macros
target_insert_hw_breakpoint and target_remove_hw_breakpoint are set
to call these functions. The argument is a struct bp_target_info *, as described in the documentation for target_insert_breakpoint. These functions work like i386_insert_watchpoint and i386_remove_watchpoint, respectively, except that they set up the debug registers to watch instruction
execution, and each hardware-assisted breakpoint always requires exactly one
debug register.
i386_stopped_by_hwbp (void)
This function returns non-zero if the inferior has some watchpoint or hardware
breakpoint that triggered. It works like i386_stopped_data_address, except
that it doesn’t record the address whose watchpoint triggered.
i386_cleanup_dregs (void)
This function clears all the reference counts, addresses, and control bits in the
mirror images of the debug registers. It doesn’t affect the actual debug registers
in the inferior process.
Notes:
1. x86 processors support setting watchpoints on I/O reads or writes. However, since no
target supports this (as of March 2001), and since enum target_hw_bp_type doesn’t
even have an enumeration for I/O watchpoints, this feature is not yet available to gdb
running on x86.
2. x86 processors can enable watchpoints locally, for the current task only, or globally, for
all the tasks. For each debug register, there’s a bit in the DR7 Debug Control register
that determines whether the associated address is watched locally or globally. The
current implementation of x86 watchpoint support in gdb always sets watchpoints to
be locally enabled, since global watchpoints might interfere with the underlying OS
and are probably unavailable in many platforms.
3.10 Checkpoints
In the abstract, a checkpoint is a point in the execution history of the program, which the
user may wish to return to at some later time.
Internally, a checkpoint is a saved copy of the program state, including whatever information is required in order to restore the program to that state at a later time. This can
be expected to include the state of registers and memory, and may include external state
such as the state of open files and devices.
There are a number of ways in which checkpoints may be implemented in gdb, eg. as
corefiles, as forked processes, and as some opaque method implemented on the target side.
A corefile can be used to save an image of target memory and register state, which can
in principle be restored later — but corefiles do not typically include information about
external entities such as open files. Currently this method is not implemented in gdb.
Chapter 4: User Interface
12
A forked process can save the state of user memory and registers, as well as some subset
of external (kernel) state. This method is used to implement checkpoints on Linux, and in
principle might be used on other systems.
Some targets, eg. simulators, might have their own built-in method for saving checkpoints, and gdb might be able to take advantage of that capability without necessarily
knowing any details of how it is done.
3.11 Observing changes in gdb internals
In order to function properly, several modules need to be notified when some changes occur
in the gdb internals. Traditionally, these modules have relied on several paradigms, the
most common ones being hooks and gdb-events. Unfortunately, none of these paradigms
was versatile enough to become the standard notification mechanism in gdb. The fact that
they only supported one “client” was also a strong limitation.
A new paradigm, based on the Observer pattern of the Design Patterns book, has therefore been implemented. The goal was to provide a new interface overcoming the issues with
the notification mechanisms previously available. This new interface needed to be strongly
typed, easy to extend, and versatile enough to be used as the standard interface when
adding new notifications.
See Appendix A [GDB Observers], page 95 for a brief description of the observers currently implemented in GDB. The rationale for the current implementation is also briefly
discussed.
4 User Interface
gdb has several user interfaces. Although the command-line interface is the most common
and most familiar, there are others.
4.1 Command Interpreter
The command interpreter in gdb is fairly simple. It is designed to allow for the set of
commands to be augmented dynamically, and also has a recursive subcommand capability,
where the first argument to a command may itself direct a lookup on a different command
list.
For instance, the ‘set’ command just starts a lookup on the setlist command list,
while ‘set thread’ recurses to the set_thread_cmd_list.
To add commands in general, use add_cmd. add_com adds to the main command list,
and should be used for those commands. The usual place to add commands is in the
_initialize_xyz routines at the ends of most source files.
To add paired ‘set’ and ‘show’ commands, use add_setshow_cmd or add_setshow_cmd_
full. The former is a slightly simpler interface which is useful when you don’t need to
further modify the new command structures, while the latter returns the new command
structures for manipulation.
Before removing commands from the command set it is a good idea to deprecate them
for some time. Use deprecate_cmd on commands or aliases to set the deprecated flag.
Chapter 4: User Interface
13
deprecate_cmd takes a struct cmd_list_element as it’s first argument. You can use the
return value from add_com or add_cmd to deprecate the command immediately after it is
created.
The first time a command is used the user will be warned and offered a replacement (if
one exists). Note that the replacement string passed to deprecate_cmd should be the full
name of the command, i.e. the entire string the user should type at the command line.
4.2 UI-Independent Output—the ui_out Functions
The ui_out functions present an abstraction level for the gdb output code. They hide
the specifics of different user interfaces supported by gdb, and thus free the programmer
from the need to write several versions of the same code, one each for every UI, to produce
output.
4.2.1 Overview and Terminology
In general, execution of each gdb command produces some sort of output, and can even
generate an input request.
Output can be generated for the following purposes:
• to display a result of an operation;
• to convey info or produce side-effects of a requested operation;
• to provide a notification of an asynchronous event (including progress indication of a
prolonged asynchronous operation);
• to display error messages (including warnings);
• to show debug data;
• to query or prompt a user for input (a special case).
This section mainly concentrates on how to build result output, although some of it also
applies to other kinds of output.
Generation of output that displays the results of an operation involves one or more of
the following:
• output of the actual data
• formatting the output as appropriate for console output, to make it easily readable by
humans
• machine oriented formatting–a more terse formatting to allow for easy parsing by programs which read gdb’s output
• annotation, whose purpose is to help legacy GUIs to identify interesting parts in the
output
The ui_out routines take care of the first three aspects. Annotations are provided by
separate annotation routines. Note that use of annotations for an interface between a GUI
and gdb is deprecated.
Output can be in the form of a single item, which we call a field; a list consisting
of identical fields; a tuple consisting of non-identical fields; or a table, which is a tuple
consisting of a header and a body. In a BNF-like form:
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14
<table> 7→
<header> <body>
<header> 7→
{ <column> }
<column> 7→
<width> <alignment> <title>
<body> 7→ {<row>}
4.2.2 General Conventions
Most ui_out routines are of type void, the exceptions are ui_out_stream_new (which
returns a pointer to the newly created object) and the make_cleanup routines.
The first parameter is always the ui_out vector object, a pointer to a struct ui_out.
The format parameter is like in printf family of functions. When it is present, there
must also be a variable list of arguments sufficient used to satisfy the % specifiers in the
supplied format.
When a character string argument is not used in a ui_out function call, a NULL pointer
has to be supplied instead.
4.2.3 Table, Tuple and List Functions
This section introduces ui_out routines for building lists, tuples and tables. The routines
to output the actual data items (fields) are presented in the next section.
To recap: A tuple is a sequence of fields, each field containing information about an
object; a list is a sequence of fields where each field describes an identical object.
Use the table functions when your output consists of a list of rows (tuples) and the
console output should include a heading. Use this even when you are listing just one object
but you still want the header.
Tables can not be nested. Tuples and lists can be nested up to a maximum of five levels.
The overall structure of the table output code is something like this:
ui_out_table_begin
ui_out_table_header
...
ui_out_table_body
ui_out_tuple_begin
ui_out_field_*
...
ui_out_tuple_end
...
ui_out_table_end
Here is the description of table-, tuple- and list-related ui_out functions:
void ui_out_table_begin (struct ui out *uiout, int nbrofcols, int
nr_rows, const char *tblid )
[Function]
The function ui_out_table_begin marks the beginning of the output of a table. It
should always be called before any other ui_out function for a given table. nbrofcols
is the number of columns in the table. nr rows is the number of rows in the table.
tblid is an optional string identifying the table. The string pointed to by tblid is
Chapter 4: User Interface
15
copied by the implementation of ui_out_table_begin, so the application can free
the string if it was malloced.
The companion function ui_out_table_end, described below, marks the end of the
table’s output.
void ui_out_table_header (struct ui out *uiout, int width, enum
ui align alignment, const char *colhdr )
[Function]
ui_out_table_header provides the header information for a single table column.
You call this function several times, one each for every column of the table, after
ui_out_table_begin, but before ui_out_table_body.
The value of width gives the column width in characters. The value of alignment is
one of left, center, and right, and it specifies how to align the header: left-justify,
center, or right-justify it. colhdr points to a string that specifies the column header;
the implementation copies that string, so column header strings in malloced storage
can be freed after the call.
void ui_out_table_body (struct ui out *uiout )
[Function]
This function delimits the table header from the table body.
void ui_out_table_end (struct ui out *uiout )
[Function]
This function signals the end of a table’s output. It should be called after the table
body has been produced by the list and field output functions.
There should be exactly one call to ui_out_table_end for each call to ui_out_table_
begin, otherwise the ui_out functions will signal an internal error.
The output of the tuples that represent the table rows must follow the call to ui_out_
table_body and precede the call to ui_out_table_end. You build a tuple by calling ui_
out_tuple_begin and ui_out_tuple_end, with suitable calls to functions which actually
output fields between them.
void ui_out_tuple_begin (struct ui out *uiout, const char *id )
[Function]
This function marks the beginning of a tuple output. id points to an optional string
that identifies the tuple; it is copied by the implementation, and so strings in malloced
storage can be freed after the call.
void ui_out_tuple_end (struct ui out *uiout )
[Function]
This function signals an end of a tuple output. There should be exactly one call to
ui_out_tuple_end for each call to ui_out_tuple_begin, otherwise an internal gdb
error will be signaled.
struct cleanup *make cleanup ui out tuple begin end (struct ui out
*uiout, const char *id )
[Function]
This function first opens the tuple and then establishes a cleanup (see Chapter 13
[Coding], page 67) to close the tuple. It provides a convenient and correct implementation of the non-portable1 code sequence:
struct cleanup *old_cleanup;
ui_out_tuple_begin (uiout, "...");
old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
uiout);
1
The function cast is not portable ISO C.
Chapter 4: User Interface
16
void ui_out_list_begin (struct ui out *uiout, const char *id )
[Function]
This function marks the beginning of a list output. id points to an optional string
that identifies the list; it is copied by the implementation, and so strings in malloced
storage can be freed after the call.
void ui_out_list_end (struct ui out *uiout )
[Function]
This function signals an end of a list output. There should be exactly one call to
ui_out_list_end for each call to ui_out_list_begin, otherwise an internal gdb
error will be signaled.
struct cleanup *make cleanup ui out list begin end (struct ui out
*uiout, const char *id )
[Function]
Similar to make_cleanup_ui_out_tuple_begin_end, this function opens a list and
then establishes cleanup (see Chapter 13 [Coding], page 67) that will close the list.list.
4.2.4 Item Output Functions
The functions described below produce output for the actual data items, or fields, which
contain information about the object.
Choose the appropriate function accordingly to your particular needs.
void ui_out_field_fmt (struct ui out *uiout, char *fldname, char
*format, ...)
[Function]
This is the most general output function. It produces the representation of the data
in the variable-length argument list according to formatting specifications in format,
a printf-like format string. The optional argument fldname supplies the name of the
field. The data items themselves are supplied as additional arguments after format.
This generic function should be used only when it is not possible to use one of the
specialized versions (see below).
void ui_out_field_int (struct ui out *uiout, const char *fldname,
int value )
[Function]
This function outputs a value of an int variable. It uses the "%d" output conversion
specification. fldname specifies the name of the field.
void ui_out_field_fmt_int (struct ui out *uiout, int width, enum
ui align alignment, const char *fldname, int value )
[Function]
This function outputs a value of an int variable. It differs from ui_out_field_int
in that the caller specifies the desired width and alignment of the output. fldname
specifies the name of the field.
void ui_out_field_core_addr (struct ui out *uiout, const char
*fldname, CORE ADDR address )
[Function]
This function outputs an address.
void ui_out_field_string (struct ui out *uiout, const char
*fldname, const char *string )
This function outputs a string using the "%s" conversion specification.
[Function]
Chapter 4: User Interface
17
Sometimes, there’s a need to compose your output piece by piece using functions that
operate on a stream, such as value_print or fprintf_symbol_filtered. These functions
accept an argument of the type struct ui_file *, a pointer to a ui_file object used to
store the data stream used for the output. When you use one of these functions, you need
a way to pass their results stored in a ui_file object to the ui_out functions. To this
end, you first create a ui_stream object by calling ui_out_stream_new, pass the stream
member of that ui_stream object to value_print and similar functions, and finally call
ui_out_field_stream to output the field you constructed. When the ui_stream object
is no longer needed, you should destroy it and free its memory by calling ui_out_stream_
delete.
struct ui_stream *ui out stream new (struct ui out *uiout )
[Function]
This function creates a new ui_stream object which uses the same output methods
as the ui_out object whose pointer is passed in uiout. It returns a pointer to the
newly created ui_stream object.
void ui_out_stream_delete (struct ui stream *streambuf )
[Function]
This functions destroys a ui_stream object specified by streambuf.
void ui_out_field_stream (struct ui out *uiout, const char
*fieldname, struct ui stream *streambuf )
[Function]
This function consumes all the data accumulated in streambuf->stream and outputs it like ui_out_field_string does. After a call to ui_out_field_stream, the
accumulated data no longer exists, but the stream is still valid and may be used for
producing more fields.
Important: If there is any chance that your code could bail out before completing output
generation and reaching the point where ui_out_stream_delete is called, it is necessary
to set up a cleanup, to avoid leaking memory and other resources. Here’s a skeleton code
to do that:
struct ui_stream *mybuf = ui_out_stream_new (uiout);
struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
...
do_cleanups (old);
If the function already has the old cleanup chain set (for other kinds of cleanups), you
just have to add your cleanup to it:
mybuf = ui_out_stream_new (uiout);
make_cleanup (ui_out_stream_delete, mybuf);
Note that with cleanups in place, you should not call ui_out_stream_delete directly,
or you would attempt to free the same buffer twice.
4.2.5 Utility Output Functions
void ui_out_field_skip (struct ui out *uiout, const char *fldname )
[Function]
This function skips a field in a table. Use it if you have to leave an empty field
without disrupting the table alignment. The argument fldname specifies a name for
the (missing) filed.
Chapter 4: User Interface
18
void ui_out_text (struct ui out *uiout, const char *string )
[Function]
This function outputs the text in string in a way that makes it easy to be read by
humans. For example, the console implementation of this method filters the text
through a built-in pager, to prevent it from scrolling off the visible portion of the
screen.
Use this function for printing relatively long chunks of text around the actual field
data: the text it produces is not aligned according to the table’s format. Use ui_out_
field_string to output a string field, and use ui_out_message, described below, to
output short messages.
void ui_out_spaces (struct ui out *uiout, int nspaces )
[Function]
This function outputs nspaces spaces. It is handy to align the text produced by
ui_out_text with the rest of the table or list.
void ui_out_message (struct ui out *uiout, int verbosity, const char
*format, ...)
[Function]
This function produces a formatted message, provided that the current verbosity level
is at least as large as given by verbosity. The current verbosity level is specified by
the user with the ‘set verbositylevel’ command.2
void ui_out_wrap_hint (struct ui out *uiout, char *indent )
[Function]
This function gives the console output filter (a paging filter) a hint of where to break
lines which are too long. Ignored for all other output consumers. indent, if non-NULL,
is the string to be printed to indent the wrapped text on the next line; it must remain
accessible until the next call to ui_out_wrap_hint, or until an explicit newline is
produced by one of the other functions. If indent is NULL, the wrapped text will not
be indented.
void ui_out_flush (struct ui out *uiout )
[Function]
This function flushes whatever output has been accumulated so far, if the UI buffers
output.
4.2.6 Examples of Use of ui_out functions
This section gives some practical examples of using the ui_out functions to generalize the
old console-oriented code in gdb. The examples all come from functions defined on the
‘breakpoints.c’ file.
This example, from the breakpoint_1 function, shows how to produce a table.
The original code was:
if (!found_a_breakpoint++)
{
annotate_breakpoints_headers ();
annotate_field (0);
printf_filtered ("Num ");
annotate_field (1);
2
As of this writing (April 2001), setting verbosity level is not yet implemented, and is always returned as
zero. So calling ui_out_message with a verbosity argument more than zero will cause the message to
never be printed.
Chapter 4: User Interface
printf_filtered ("Type
annotate_field (2);
printf_filtered ("Disp ");
annotate_field (3);
printf_filtered ("Enb ");
if (addressprint)
{
annotate_field (4);
printf_filtered ("Address
}
annotate_field (5);
printf_filtered ("What\n");
19
");
");
annotate_breakpoints_table ();
}
Here’s the new version:
nr_printable_breakpoints = ...;
if (addressprint)
ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
else
ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");
if (nr_printable_breakpoints > 0)
annotate_breakpoints_headers ();
if (nr_printable_breakpoints > 0)
annotate_field (0);
ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */
if (nr_printable_breakpoints > 0)
annotate_field (1);
ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */
if (nr_printable_breakpoints > 0)
annotate_field (2);
ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */
if (nr_printable_breakpoints > 0)
annotate_field (3);
ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */
if (addressprint)
{
if (nr_printable_breakpoints > 0)
annotate_field (4);
if (TARGET_ADDR_BIT <= 32)
ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */
else
ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */
}
if (nr_printable_breakpoints > 0)
annotate_field (5);
ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */
ui_out_table_body (uiout);
if (nr_printable_breakpoints > 0)
annotate_breakpoints_table ();
This example, from the print_one_breakpoint function, shows how to produce the
actual data for the table whose structure was defined in the above example. The original
code was:
annotate_record ();
Chapter 4: User Interface
20
annotate_field (0);
printf_filtered ("%-3d ", b->number);
annotate_field (1);
if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
|| ((int) b->type != bptypes[(int) b->type].type))
internal_error ("bptypes table does not describe type #%d.",
(int)b->type);
printf_filtered ("%-14s ", bptypes[(int)b->type].description);
annotate_field (2);
printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
annotate_field (3);
printf_filtered ("%-3c ", bpenables[(int)b->enable]);
...
This is the new version:
annotate_record ();
ui_out_tuple_begin (uiout, "bkpt");
annotate_field (0);
ui_out_field_int (uiout, "number", b->number);
annotate_field (1);
if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
|| ((int) b->type != bptypes[(int) b->type].type))
internal_error ("bptypes table does not describe type #%d.",
(int) b->type);
ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
annotate_field (2);
ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
annotate_field (3);
ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
...
This example, also from print_one_breakpoint, shows how to produce a complicated
output field using the print_expression functions which requires a stream to be passed.
It also shows how to automate stream destruction with cleanups. The original code was:
annotate_field (5);
print_expression (b->exp, gdb_stdout);
The new version is:
struct ui_stream *stb = ui_out_stream_new (uiout);
struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
...
annotate_field (5);
print_expression (b->exp, stb->stream);
ui_out_field_stream (uiout, "what", local_stream);
This example, also from print_one_breakpoint, shows how to use ui_out_text and
ui_out_field_string. The original code was:
annotate_field (5);
if (b->dll_pathname == NULL)
printf_filtered ("<any library> ");
else
printf_filtered ("library \"%s\" ", b->dll_pathname);
It became:
annotate_field (5);
if (b->dll_pathname == NULL)
{
ui_out_field_string (uiout, "what", "<any library>");
ui_out_spaces (uiout, 1);
Chapter 5: libgdb
21
}
else
{
ui_out_text (uiout, "library \"");
ui_out_field_string (uiout, "what", b->dll_pathname);
ui_out_text (uiout, "\" ");
}
The following example from print_one_breakpoint shows how to use ui_out_field_
int and ui_out_spaces. The original code was:
annotate_field (5);
if (b->forked_inferior_pid != 0)
printf_filtered ("process %d ", b->forked_inferior_pid);
It became:
annotate_field (5);
if (b->forked_inferior_pid != 0)
{
ui_out_text (uiout, "process ");
ui_out_field_int (uiout, "what", b->forked_inferior_pid);
ui_out_spaces (uiout, 1);
}
Here’s an example of using ui_out_field_string. The original code was:
annotate_field (5);
if (b->exec_pathname != NULL)
printf_filtered ("program \"%s\" ", b->exec_pathname);
It became:
annotate_field (5);
if (b->exec_pathname !=
{
ui_out_text (uiout,
ui_out_field_string
ui_out_text (uiout,
}
NULL)
"program \"");
(uiout, "what", b->exec_pathname);
"\" ");
Finally, here’s an example of printing an address. The original code:
annotate_field (4);
printf_filtered ("%s ",
hex_string_custom ((unsigned long) b->address, 8));
It became:
annotate_field (4);
ui_out_field_core_addr (uiout, "Address", b->address);
4.3 Console Printing
4.4 TUI
5 libgdb
5.1 libgdb 1.0
libgdb 1.0 was an abortive project of years ago. The theory was to provide an API to
gdb’s functionality.
Chapter 5: libgdb
22
5.2 libgdb 2.0
libgdb 2.0 is an ongoing effort to update gdb so that is better able to support graphical
and other environments.
Since libgdb development is on-going, its architecture is still evolving. The following
components have so far been identified:
• Observer - ‘gdb-events.h’.
• Builder - ‘ui-out.h’
• Event Loop - ‘event-loop.h’
• Library - ‘gdb.h’
The model that ties these components together is described below.
5.3 The libgdb Model
A client of libgdb interacts with the library in two ways.
• As an observer (using ‘gdb-events’) receiving notifications from libgdb of any internal
state changes (break point changes, run state, etc).
• As a client querying libgdb (using the ‘ui-out’ builder) to obtain various status values
from gdb.
Since libgdb could have multiple clients (e.g., a GUI supporting the existing gdb CLI),
those clients must co-operate when controlling libgdb. In particular, a client must ensure
that libgdb is idle (i.e. no other client is using libgdb) before responding to a ‘gdb-event’
by making a query.
5.4 CLI support
At present gdb’s CLI is very much entangled in with the core of libgdb. Consequently, a
client wishing to include the CLI in their interface needs to carefully co-ordinate its own
and the CLI’s requirements.
It is suggested that the client set libgdb up to be bi-modal (alternate between CLI and
client query modes). The notes below sketch out the theory:
• The client registers itself as an observer of libgdb.
• The client create and install cli-out builder using its own versions of the ui-file
gdb_stderr, gdb_stdtarg and gdb_stdout streams.
• The client creates a separate custom ui-out builder that is only used while making
direct queries to libgdb.
When the client receives input intended for the CLI, it simply passes it along. Since the
cli-out builder is installed by default, all the CLI output in response to that command
is routed (pronounced rooted) through to the client controlled gdb_stdout et. al. streams.
At the same time, the client is kept abreast of internal changes by virtue of being a libgdb
observer.
The only restriction on the client is that it must wait until libgdb becomes idle before
initiating any queries (using the client’s custom builder).
Chapter 6: Symbol Handling
23
5.5 libgdb components
Observer - ‘gdb-events.h’
‘gdb-events’ provides the client with a very raw mechanism that can be used to implement
an observer. At present it only allows for one observer and that observer must, internally,
handle the need to delay the processing of any event notifications until after libgdb has
finished the current command.
Builder - ‘ui-out.h’
‘ui-out’ provides the infrastructure necessary for a client to create a builder. That builder
is then passed down to libgdb when doing any queries.
Event Loop - ‘event-loop.h’
‘event-loop’, currently non-re-entrant, provides a simple event loop. A client would need
to either plug its self into this loop or, implement a new event-loop that GDB would use.
The event-loop will eventually be made re-entrant. This is so that gdb can better handle
the problem of some commands blocking instead of returning.
Library - ‘gdb.h’
‘libgdb’ is the most obvious component of this system. It provides the query interface.
Each function is parameterized by a ui-out builder. The result of the query is constructed
using that builder before the query function returns.
6 Symbol Handling
Symbols are a key part of gdb’s operation. Symbols include variables, functions, and types.
6.1 Symbol Reading
gdb reads symbols from symbol files. The usual symbol file is the file containing the
program which gdb is debugging. gdb can be directed to use a different file for symbols
(with the ‘symbol-file’ command), and it can also read more symbols via the ‘add-file’
and ‘load’ commands, or while reading symbols from shared libraries.
Symbol files are initially opened by code in ‘symfile.c’ using the BFD library (see
Chapter 12 [Support Libraries], page 65). BFD identifies the type of the file by examining
its header. find_sym_fns then uses this identification to locate a set of symbol-reading
functions.
Symbol-reading modules identify themselves to gdb by calling add_symtab_fns during
their module initialization. The argument to add_symtab_fns is a struct sym_fns which
contains the name (or name prefix) of the symbol format, the length of the prefix, and
pointers to four functions. These functions are called at various times to process symbol
files whose identification matches the specified prefix.
The functions supplied by each module are:
Chapter 6: Symbol Handling
24
xyz _symfile_init(struct sym_fns *sf)
Called from symbol_file_add when we are about to read a new symbol file.
This function should clean up any internal state (possibly resulting from halfread previous files, for example) and prepare to read a new symbol file. Note
that the symbol file which we are reading might be a new “main” symbol file, or
might be a secondary symbol file whose symbols are being added to the existing
symbol table.
The argument to xyz _symfile_init is a newly allocated struct sym_fns
whose bfd field contains the BFD for the new symbol file being read. Its
private field has been zeroed, and can be modified as desired. Typically,
a struct of private information will be malloc’d, and a pointer to it will be
placed in the private field.
There is no result from xyz _symfile_init, but it can call error if it detects
an unavoidable problem.
xyz _new_init()
Called from symbol_file_add when discarding existing symbols. This function
needs only handle the symbol-reading module’s internal state; the symbol table
data structures visible to the rest of gdb will be discarded by symbol_file_add.
It has no arguments and no result. It may be called after xyz _symfile_init,
if a new symbol table is being read, or may be called alone if all symbols are
simply being discarded.
xyz _symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
Called from symbol_file_add to actually read the symbols from a symbol-file
into a set of psymtabs or symtabs.
sf points to the struct sym_fns originally passed to xyz _sym_init for possible
initialization. addr is the offset between the file’s specified start address and
its true address in memory. mainline is 1 if this is the main symbol table
being read, and 0 if a secondary symbol file (e.g., shared library or dynamically
loaded file) is being read.
In addition, if a symbol-reading module creates psymtabs when xyz symfile read is
called, these psymtabs will contain a pointer to a function xyz _psymtab_to_symtab, which
can be called from any point in the gdb symbol-handling code.
xyz _psymtab_to_symtab (struct partial_symtab *pst)
Called from psymtab_to_symtab (or the PSYMTAB_TO_SYMTAB macro) if the
psymtab has not already been read in and had its pst->symtab pointer set.
The argument is the psymtab to be fleshed-out into a symtab. Upon return,
pst->readin should have been set to 1, and pst->symtab should contain a
pointer to the new corresponding symtab, or zero if there were no symbols in
that part of the symbol file.
6.2 Partial Symbol Tables
gdb has three types of symbol tables:
• Full symbol tables (symtabs). These contain the main information about symbols and
addresses.
Chapter 6: Symbol Handling
25
• Partial symbol tables (psymtabs). These contain enough information to know when to
read the corresponding part of the full symbol table.
• Minimal symbol tables (msymtabs). These contain information gleaned from nondebugging symbols.
This section describes partial symbol tables.
A psymtab is constructed by doing a very quick pass over an executable file’s debugging
information. Small amounts of information are extracted—enough to identify which parts
of the symbol table will need to be re-read and fully digested later, when the user needs
the information. The speed of this pass causes gdb to start up very quickly. Later, as the
detailed rereading occurs, it occurs in small pieces, at various times, and the delay therefrom
is mostly invisible to the user.
The symbols that show up in a file’s psymtab should be, roughly, those visible to the
debugger’s user when the program is not running code from that file. These include external
symbols and types, static symbols and types, and enum values declared at file scope.
The psymtab also contains the range of instruction addresses that the full symbol table
would represent.
The idea is that there are only two ways for the user (or much of the code in the debugger)
to reference a symbol:
• By its address (e.g., execution stops at some address which is inside a function in this
file). The address will be noticed to be in the range of this psymtab, and the full
symtab will be read in. find_pc_function, find_pc_line, and other find_pc_...
functions handle this.
• By its name (e.g., the user asks to print a variable, or set a breakpoint on a function).
Global names and file-scope names will be found in the psymtab, which will cause the
symtab to be pulled in. Local names will have to be qualified by a global name, or a
file-scope name, in which case we will have already read in the symtab as we evaluated
the qualifier. Or, a local symbol can be referenced when we are “in” a local scope, in
which case the first case applies. lookup_symbol does most of the work here.
The only reason that psymtabs exist is to cause a symtab to be read in at the right
moment. Any symbol that can be elided from a psymtab, while still causing that to happen,
should not appear in it. Since psymtabs don’t have the idea of scope, you can’t put local
symbols in them anyway. Psymtabs don’t have the idea of the type of a symbol, either, so
types need not appear, unless they will be referenced by name.
It is a bug for gdb to behave one way when only a psymtab has been read, and another
way if the corresponding symtab has been read in. Such bugs are typically caused by a
psymtab that does not contain all the visible symbols, or which has the wrong instruction
address ranges.
The psymtab for a particular section of a symbol file (objfile) could be thrown away after
the symtab has been read in. The symtab should always be searched before the psymtab,
so the psymtab will never be used (in a bug-free environment). Currently, psymtabs are
allocated on an obstack, and all the psymbols themselves are allocated in a pair of large
arrays on an obstack, so there is little to be gained by trying to free them unless you want
to do a lot more work.
Chapter 6: Symbol Handling
26
6.3 Types
Fundamental Types (e.g., FT_VOID, FT_BOOLEAN).
These are the fundamental types that gdb uses internally. Fundamental types from the
various debugging formats (stabs, ELF, etc) are mapped into one of these. They are basically a union of all fundamental types that gdb knows about for all the languages that
gdb knows about.
Type Codes (e.g., TYPE_CODE_PTR, TYPE_CODE_ARRAY).
Each time gdb builds an internal type, it marks it with one of these types. The type may
be a fundamental type, such as TYPE_CODE_INT, or a derived type, such as TYPE_CODE_PTR
which is a pointer to another type. Typically, several FT_* types map to one TYPE_CODE_*
type, and are distinguished by other members of the type struct, such as whether the type
is signed or unsigned, and how many bits it uses.
Builtin Types (e.g., builtin_type_void, builtin_type_char).
These are instances of type structs that roughly correspond to fundamental types and are
created as global types for gdb to use for various ugly historical reasons. We eventually want
to eliminate these. Note for example that builtin_type_int initialized in ‘gdbtypes.c’
is basically the same as a TYPE_CODE_INT type that is initialized in ‘c-lang.c’ for an
FT_INTEGER fundamental type. The difference is that the builtin_type is not associated
with any particular objfile, and only one instance exists, while ‘c-lang.c’ builds as many
TYPE_CODE_INT types as needed, with each one associated with some particular objfile.
6.4 Object File Formats
6.4.1 a.out
The a.out format is the original file format for Unix. It consists of three sections: text,
data, and bss, which are for program code, initialized data, and uninitialized data, respectively.
The a.out format is so simple that it doesn’t have any reserved place for debugging
information. (Hey, the original Unix hackers used ‘adb’, which is a machine-language debugger!) The only debugging format for a.out is stabs, which is encoded as a set of normal
symbols with distinctive attributes.
The basic a.out reader is in ‘dbxread.c’.
6.4.2 COFF
The COFF format was introduced with System V Release 3 (SVR3) Unix. COFF files may
have multiple sections, each prefixed by a header. The number of sections is limited.
The COFF specification includes support for debugging. Although this was a step forward, the debugging information was woefully limited. For instance, it was not possible to
represent code that came from an included file.
The COFF reader is in ‘coffread.c’.
Chapter 6: Symbol Handling
27
6.4.3 ECOFF
ECOFF is an extended COFF originally introduced for Mips and Alpha workstations.
The basic ECOFF reader is in ‘mipsread.c’.
6.4.4 XCOFF
The IBM RS/6000 running AIX uses an object file format called XCOFF. The COFF
sections, symbols, and line numbers are used, but debugging symbols are dbx-style stabs
whose strings are located in the .debug section (rather than the string table). For more
information, see section “Top” in The Stabs Debugging Format.
The shared library scheme has a clean interface for figuring out what shared libraries
are in use, but the catch is that everything which refers to addresses (symbol tables and
breakpoints at least) needs to be relocated for both shared libraries and the main executable.
At least using the standard mechanism this can only be done once the program has been
run (or the core file has been read).
6.4.5 PE
Windows 95 and NT use the PE (Portable Executable) format for their executables. PE is
basically COFF with additional headers.
While BFD includes special PE support, gdb needs only the basic COFF reader.
6.4.6 ELF
The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar to COFF in
being organized into a number of sections, but it removes many of COFF’s limitations.
The basic ELF reader is in ‘elfread.c’.
6.4.7 SOM
SOM is HP’s object file and debug format (not to be confused with IBM’s SOM, which is
a cross-language ABI).
The SOM reader is in ‘hpread.c’.
6.4.8 Other File Formats
Other file formats that have been supported by gdb include Netware Loadable Modules
(‘nlmread.c’).
6.5 Debugging File Formats
This section describes characteristics of debugging information that are independent of the
object file format.
6.5.1 stabs
stabs started out as special symbols within the a.out format. Since then, it has been
encapsulated into other file formats, such as COFF and ELF.
While ‘dbxread.c’ does some of the basic stab processing, including for encapsulated
versions, ‘stabsread.c’ does the real work.
Chapter 6: Symbol Handling
28
6.5.2 COFF
The basic COFF definition includes debugging information. The level of support is minimal
and non-extensible, and is not often used.
6.5.3 Mips debug (Third Eye)
ECOFF includes a definition of a special debug format.
The file ‘mdebugread.c’ implements reading for this format.
6.5.4 DWARF 1
DWARF 1 is a debugging format that was originally designed to be used with ELF in SVR4
systems.
The DWARF 1 reader is in ‘dwarfread.c’.
6.5.5 DWARF 2
DWARF 2 is an improved but incompatible version of DWARF 1.
The DWARF 2 reader is in ‘dwarf2read.c’.
6.5.6 SOM
Like COFF, the SOM definition includes debugging information.
6.6 Adding a New Symbol Reader to gdb
If you are using an existing object file format (a.out, COFF, ELF, etc), there is probably
little to be done.
If you need to add a new object file format, you must first add it to BFD. This is beyond
the scope of this document.
You must then arrange for the BFD code to provide access to the debugging symbols.
Generally gdb will have to call swapping routines from BFD and a few other BFD internal
routines to locate the debugging information. As much as possible, gdb should not depend
on the BFD internal data structures.
For some targets (e.g., COFF), there is a special transfer vector used to call swapping
routines, since the external data structures on various platforms have different sizes and
layouts. Specialized routines that will only ever be implemented by one object file format
may be called directly. This interface should be described in a file ‘bfd/libxyz.h’, which
is included by gdb.
6.7 Memory Management for Symbol Files
Most memory associated with a loaded symbol file is stored on its objfile_obstack. This
includes symbols, types, namespace data, and other information produced by the symbol
readers.
Because this data lives on the objfile’s obstack, it is automatically released when the
objfile is unloaded or reloaded. Therefore one objfile must not reference symbol or type
data from another objfile; they could be unloaded at different times.
Chapter 7: Language Support
29
User convenience variables, et cetera, have associated types. Normally these types live
in the associated objfile. However, when the objfile is unloaded, those types are deep copied
to global memory, so that the values of the user variables and history items are not lost.
7 Language Support
gdb’s language support is mainly driven by the symbol reader, although it is possible for
the user to set the source language manually.
gdb chooses the source language by looking at the extension of the file recorded in
the debug info; ‘.c’ means C, ‘.f’ means Fortran, etc. It may also use a special-purpose
language identifier if the debug format supports it, like with DWARF.
7.1 Adding a Source Language to gdb
To add other languages to gdb’s expression parser, follow the following steps:
Create the expression parser.
This should reside in a file ‘lang-exp.y’. Routines for building parsed expressions into a union exp_element list are in ‘parse.c’.
Since we can’t depend upon everyone having Bison, and YACC produces parsers
that define a bunch of global names, the following lines must be included at the
top of the YACC parser, to prevent the various parsers from defining the same
global names:
#define
#define
#define
#define
#define
#define
#define
#define
#define
#define
#define
#define
#define
#define
#define
#define
yyparse
yylex
yyerror
yylval
yychar
yydebug
yypact
yyr1
yyr2
yydef
yychk
yypgo
yyact
yyexca
yyerrflag
yynerrs
lang _parse
lang _lex
lang _error
lang _lval
lang _char
lang _debug
lang _pact
lang _r1
lang _r2
lang _def
lang _chk
lang _pgo
lang _act
lang _exca
lang _errflag
lang _nerrs
At the bottom of your parser, define a struct language_defn and initialize it
with the right values for your language. Define an initialize_lang routine
and have it call ‘add_language(lang _language_defn)’ to tell the rest of gdb
that your language exists. You’ll need some other supporting variables and
functions, which will be used via pointers from your lang _language_defn.
See the declaration of struct language_defn in ‘language.h’, and the other
‘*-exp.y’ files, for more information.
Add any evaluation routines, if necessary
If you need new opcodes (that represent the operations of the language), add
them to the enumerated type in ‘expression.h’. Add support code for these
Chapter 8: Host Definition
30
operations in the evaluate_subexp function defined in the file ‘eval.c’. Add
cases for new opcodes in two functions from ‘parse.c’: prefixify_subexp and
length_of_subexp. These compute the number of exp_elements that a given
operation takes up.
Update some existing code
Add an enumerated identifier for your language to the enumerated type enum
language in ‘defs.h’.
Update the routines in ‘language.c’ so your language is included. These routines include type predicates and such, which (in some cases) are language
dependent. If your language does not appear in the switch statement, an error
is reported.
Also included in ‘language.c’ is the code that updates the variable current_
language, and the routines that translate the language_lang enumerated identifier into a printable string.
Update the function _initialize_language to include your language. This
function picks the default language upon startup, so is dependent upon which
languages that gdb is built for.
Update allocate_symtab in ‘symfile.c’ and/or symbol-reading code so that
the language of each symtab (source file) is set properly. This is used to determine the language to use at each stack frame level. Currently, the language is
set based upon the extension of the source file. If the language can be better
inferred from the symbol information, please set the language of the symtab in
the symbol-reading code.
Add helper code to print_subexp (in ‘expprint.c’) to handle any new expression opcodes you have added to ‘expression.h’. Also, add the printed
representations of your operators to op_print_tab.
Add a place of call
Add a call to lang _parse() and lang _error in parse_exp_1 (defined in
‘parse.c’).
Use macros to trim code
The user has the option of building gdb for some or all of the languages. If the
user decides to build gdb for the language lang, then every file dependent on
‘language.h’ will have the macro _LANG_lang defined in it. Use #ifdefs to
leave out large routines that the user won’t need if he or she is not using your
language.
Note that you do not need to do this in your YACC parser, since if gdb is not
build for lang, then ‘lang-exp.tab.o’ (the compiled form of your parser) is not
linked into gdb at all.
See the file ‘configure.in’ for how gdb is configured for different languages.
Edit ‘Makefile.in’
Add dependencies in ‘Makefile.in’. Make sure you update the macro variables
such as HFILES and OBJS, otherwise your code may not get linked in, or, worse
yet, it may not get tarred into the distribution!
Chapter 8: Host Definition
31
8 Host Definition
With the advent of Autoconf, it’s rarely necessary to have host definition machinery anymore. The following information is provided, mainly, as an historical reference.
8.1 Adding a New Host
gdb’s host configuration support normally happens via Autoconf. New host-specific definitions should not be needed. Older hosts gdb still use the host-specific definitions and files
listed below, but these mostly exist for historical reasons, and will eventually disappear.
‘gdb/config/arch /xyz.mh’
This file once contained both host and native configuration information (see
Chapter 11 [Native Debugging], page 61) for the machine xyz. The host configuration information is now handed by Autoconf.
Host configuration information included a definition of XM_FILE=xm-xyz.h and
possibly definitions for CC, SYSV_DEFINE, XM_CFLAGS, XM_ADD_FILES, XM_CLIBS,
XM_CDEPS, etc.; see ‘Makefile.in’.
New host only configurations do not need this file.
‘gdb/config/arch /xm-xyz.h’
This file once contained definitions and includes required when hosting gdb on
machine xyz. Those definitions and includes are now handled by Autoconf.
New host and native configurations do not need this file.
Maintainer’s note: Some hosts continue to use the ‘xm-xyz.h’ file to define
the macros HOST FLOAT FORMAT, HOST DOUBLE FORMAT and
HOST LONG DOUBLE FORMAT. That code also needs to be replaced with
either an Autoconf or run-time test.
Generic Host Support Files
There are some “generic” versions of routines that can be used by various systems. These
can be customized in various ways by macros defined in your ‘xm-xyz.h’ file. If these
routines work for the xyz host, you can just include the generic file’s name (with ‘.o’, not
‘.c’) in XDEPFILES.
Otherwise, if your machine needs custom support routines, you will need to write routines
that perform the same functions as the generic file. Put them into xyz -xdep.c, and put
xyz -xdep.o into XDEPFILES.
‘ser-unix.c’
This contains serial line support for Unix systems. This is always included, via
the makefile variable SER_HARDWIRE; override this variable in the ‘.mh’ file to
avoid it.
‘ser-go32.c’
This contains serial line support for 32-bit programs running under DOS, using
the DJGPP (a.k.a. GO32) execution environment.
‘ser-tcp.c’
This contains generic TCP support using sockets.
Chapter 8: Host Definition
32
8.2 Host Conditionals
When gdb is configured and compiled, various macros are defined or left undefined, to
control compilation based on the attributes of the host system. These macros and their
meanings (or if the meaning is not documented here, then one of the source files where they
are used is indicated) are:
gdbINIT_FILENAME
The default name of gdb’s initialization file (normally ‘.gdbinit’).
NO_STD_REGS
This macro is deprecated.
SIGWINCH_HANDLER
If your host defines SIGWINCH, you can define this to be the name of a function
to be called if SIGWINCH is received.
SIGWINCH_HANDLER_BODY
Define this to expand into code that will define the function named by the
expansion of SIGWINCH_HANDLER.
ALIGN_STACK_ON_STARTUP
Define this if your system is of a sort that will crash in tgetent if the stack
happens not to be longword-aligned when main is called. This is a rare situation,
but is known to occur on several different types of systems.
CRLF_SOURCE_FILES
Define this if host files use \r\n rather than \n as a line terminator. This will
cause source file listings to omit \r characters when printing and it will allow
\r\n line endings of files which are “sourced” by gdb. It must be possible to
open files in binary mode using O_BINARY or, for fopen, "rb".
DEFAULT_PROMPT
The default value of the prompt string (normally "(gdb) ").
DEV_TTY
The name of the generic TTY device, defaults to "/dev/tty".
FOPEN_RB
Define this if binary files are opened the same way as text files.
HAVE_MMAP
In some cases, use the system call mmap for reading symbol tables. For some
machines this allows for sharing and quick updates.
HAVE_TERMIO
Define this if the host system has termio.h.
INT_MAX
INT_MIN
LONG_MAX
UINT_MAX
ULONG_MAX
Values for host-side constants.
ISATTY
Substitute for isatty, if not available.
Chapter 8: Host Definition
LONGEST
33
This is the longest integer type available on the host. If not defined, it will
default to long long or long, depending on CC_HAS_LONG_LONG.
CC_HAS_LONG_LONG
Define this if the host C compiler supports long long. This is set by the
configure script.
PRINTF_HAS_LONG_LONG
Define this if the host can handle printing of long long integers via the printf
format conversion specifier ll. This is set by the configure script.
HAVE_LONG_DOUBLE
Define this if the host C compiler supports long double. This is set by the
configure script.
PRINTF_HAS_LONG_DOUBLE
Define this if the host can handle printing of long double float-point numbers
via the printf format conversion specifier Lg. This is set by the configure
script.
SCANF_HAS_LONG_DOUBLE
Define this if the host can handle the parsing of long double float-point numbers
via the scanf format conversion specifier Lg. This is set by the configure script.
LSEEK_NOT_LINEAR
Define this if lseek (n) does not necessarily move to byte number n in the
file. This is only used when reading source files. It is normally faster to define
CRLF_SOURCE_FILES when possible.
L_SET
This macro is used as the argument to lseek (or, most commonly, bfd_seek).
FIXME, should be replaced by SEEK SET instead, which is the POSIX equivalent.
NORETURN
If defined, this should be one or more tokens, such as volatile, that can be
used in both the declaration and definition of functions to indicate that they
never return. The default is already set correctly if compiling with GCC. This
will almost never need to be defined.
ATTR_NORETURN
If defined, this should be one or more tokens, such as __attribute__
((noreturn)), that can be used in the declarations of functions to indicate
that they never return. The default is already set correctly if compiling with
GCC. This will almost never need to be defined.
SEEK_CUR
SEEK_SET
Define these to appropriate value for the system lseek, if not already defined.
STOP_SIGNAL
This is the signal for stopping gdb. Defaults to SIGTSTP. (Only redefined for
the Convex.)
USG
Means that System V (prior to SVR4) include files are in use. (FIXME: This
symbol is abused in ‘infrun.c’, ‘regex.c’, and ‘utils.c’ for other things, at
the moment.)
Chapter 9: Target Architecture Definition
lint
Define this to help placate lint in some situations.
volatile
Define this to override the defaults of __volatile__ or /**/.
34
9 Target Architecture Definition
gdb’s target architecture defines what sort of machine-language programs gdb can work
with, and how it works with them.
The target architecture object is implemented as the C structure struct gdbarch *.
The structure, and its methods, are generated using the Bourne shell script ‘gdbarch.sh’.
9.1 Operating System ABI Variant Handling
gdb provides a mechanism for handling variations in OS ABIs. An OS ABI variant may
have influence over any number of variables in the target architecture definition. There are
two major components in the OS ABI mechanism: sniffers and handlers.
A sniffer examines a file matching a BFD architecture/flavour pair (the architecture
may be wildcarded) in an attempt to determine the OS ABI of that file. Sniffers with a
wildcarded architecture are considered to be generic, while sniffers for a specific architecture
are considered to be specific. A match from a specific sniffer overrides a match from a generic
sniffer. Multiple sniffers for an architecture/flavour may exist, in order to differentiate
between two different operating systems which use the same basic file format. The OS ABI
framework provides a generic sniffer for ELF-format files which examines the EI_OSABI field
of the ELF header, as well as note sections known to be used by several operating systems.
A handler is used to fine-tune the gdbarch structure for the selected OS ABI. There
may be only one handler for a given OS ABI for each BFD architecture.
The following OS ABI variants are defined in ‘osabi.h’:
GDB_OSABI_UNKNOWN
The ABI of the inferior is unknown. The default gdbarch settings for the
architecture will be used.
GDB_OSABI_SVR4
UNIX System V Release 4
GDB_OSABI_HURD
GNU using the Hurd kernel
GDB_OSABI_SOLARIS
Sun Solaris
GDB_OSABI_OSF1
OSF/1, including Digital UNIX and Compaq Tru64 UNIX
GDB_OSABI_LINUX
GNU using the Linux kernel
GDB_OSABI_FREEBSD_AOUT
FreeBSD using the a.out executable format
Chapter 9: Target Architecture Definition
35
GDB_OSABI_FREEBSD_ELF
FreeBSD using the ELF executable format
GDB_OSABI_NETBSD_AOUT
NetBSD using the a.out executable format
GDB_OSABI_NETBSD_ELF
NetBSD using the ELF executable format
GDB_OSABI_WINCE
Windows CE
GDB_OSABI_GO32
DJGPP
GDB_OSABI_NETWARE
Novell NetWare
GDB_OSABI_ARM_EABI_V1
ARM Embedded ABI version 1
GDB_OSABI_ARM_EABI_V2
ARM Embedded ABI version 2
GDB_OSABI_ARM_APCS
Generic ARM Procedure Call Standard
Here are the functions that make up the OS ABI framework:
const char *gdbarch osabi name (enum gdb osabi osabi )
[Function]
Return the name of the OS ABI corresponding to osabi.
void gdbarch_register_osabi (enum bfd architecture arch, unsigned
[Function]
long machine, enum gdb osabi osabi, void (*init_osabi )(struct
gdbarch info info, struct gdbarch *gdbarch ))
Register the OS ABI handler specified by init osabi for the architecture, machine
type and OS ABI specified by arch, machine and osabi. In most cases, a value of
zero for the machine type, which implies the architecture’s default machine type, will
suffice.
void gdbarch_register_osabi_sniffer (enum bfd architecture
[Function]
arch, enum bfd flavour flavour, enum gdb osabi (*sniffer )(bfd *abfd ))
Register the OS ABI file sniffer specified by sniffer for the BFD architecture/flavour
pair specified by arch and flavour. If arch is bfd_arch_unknown, the sniffer is considered to be generic, and is allowed to examine flavour-flavoured files for any architecture.
enum gdb_osabi gdbarch lookup osabi (bfd *abfd )
[Function]
Examine the file described by abfd to determine its OS ABI. The value GDB_OSABI_
UNKNOWN is returned if the OS ABI cannot be determined.
void gdbarch_init_osabi (struct gdbarch info info, struct gdbarch
*gdbarch, enum gdb osabi osabi )
[Function]
Invoke the OS ABI handler corresponding to osabi to fine-tune the gdbarch structure
specified by gdbarch. If a handler corresponding to osabi has not been registered
Chapter 9: Target Architecture Definition
36
for gdbarch’s architecture, a warning will be issued and the debugging session will
continue with the defaults already established for gdbarch.
9.2 Registers and Memory
gdb’s model of the target machine is rather simple. gdb assumes the machine includes a
bank of registers and a block of memory. Each register may have a different size.
gdb does not have a magical way to match up with the compiler’s idea of which registers
are which; however, it is critical that they do match up accurately. The only way to make
this work is to get accurate information about the order that the compiler uses, and to
reflect that in the REGISTER_NAME and related macros.
gdb can handle big-endian, little-endian, and bi-endian architectures.
9.3 Pointers Are Not Always Addresses
On almost all 32-bit architectures, the representation of a pointer is indistinguishable from
the representation of some fixed-length number whose value is the byte address of the
object pointed to. On such machines, the words “pointer” and “address” can be used
interchangeably. However, architectures with smaller word sizes are often cramped for
address space, so they may choose a pointer representation that breaks this identity, and
allows a larger code address space.
For example, the Renesas D10V is a 16-bit VLIW processor whose instructions are 32
bits long3 . If the D10V used ordinary byte addresses to refer to code locations, then the
processor would only be able to address 64kb of instructions. However, since instructions
must be aligned on four-byte boundaries, the low two bits of any valid instruction’s byte
address are always zero—byte addresses waste two bits. So instead of byte addresses, the
D10V uses word addresses—byte addresses shifted right two bits—to refer to code. Thus,
the D10V can use 16-bit words to address 256kb of code space.
However, this means that code pointers and data pointers have different forms on the
D10V. The 16-bit word 0xC020 refers to byte address 0xC020 when used as a data address,
but refers to byte address 0x30080 when used as a code address.
(The D10V also uses separate code and data address spaces, which also affects the
correspondence between pointers and addresses, but we’re going to ignore that here; this
example is already too long.)
To cope with architectures like this—the D10V is not the only one!—gdb tries to distinguish between addresses, which are byte numbers, and pointers, which are the target’s
representation of an address of a particular type of data. In the example above, 0xC020
is the pointer, which refers to one of the addresses 0xC020 or 0x30080, depending on the
type imposed upon it. gdb provides functions for turning a pointer into an address and
vice versa, in the appropriate way for the current architecture.
Unfortunately, since addresses and pointers are identical on almost all processors, this
distinction tends to bit-rot pretty quickly. Thus, each time you port gdb to an architecture
3
Some D10V instructions are actually pairs of 16-bit sub-instructions. However, since you can’t jump
into the middle of such a pair, code addresses can only refer to full 32 bit instructions, which is what
matters in this explanation.
Chapter 9: Target Architecture Definition
37
which does distinguish between pointers and addresses, you’ll probably need to clean up
some architecture-independent code.
Here are functions which convert between pointers and addresses:
CORE_ADDR extract_typed_address (void *buf, struct type *type )
[Function]
Treat the bytes at buf as a pointer or reference of type type, and return the address
it represents, in a manner appropriate for the current architecture. This yields an
address gdb can use to read target memory, disassemble, etc. Note that buf refers
to a buffer in gdb’s memory, not the inferior’s.
For example, if the current architecture is the Intel x86, this function extracts a littleendian integer of the appropriate length from buf and returns it. However, if the
current architecture is the D10V, this function will return a 16-bit integer extracted
from buf, multiplied by four if type is a pointer to a function.
If type is not a pointer or reference type, then this function will signal an internal
error.
CORE_ADDR store_typed_address (void *buf, struct type *type,
CORE ADDR addr )
[Function]
Store the address addr in buf, in the proper format for a pointer of type type in
the current architecture. Note that buf refers to a buffer in gdb’s memory, not the
inferior’s.
For example, if the current architecture is the Intel x86, this function stores addr
unmodified as a little-endian integer of the appropriate length in buf. However, if
the current architecture is the D10V, this function divides addr by four if type is a
pointer to a function, and then stores it in buf.
If type is not a pointer or reference type, then this function will signal an internal
error.
CORE_ADDR value_as_address (struct value *val )
[Function]
Assuming that val is a pointer, return the address it represents, as appropriate for
the current architecture.
This function actually works on integral values, as well as pointers. For pointers,
it performs architecture-specific conversions as described above for extract_typed_
address.
CORE_ADDR value_from_pointer (struct type *type, CORE ADDR
addr )
[Function]
Create and return a value representing a pointer of type type to the address addr, as
appropriate for the current architecture. This function performs architecture-specific
conversions as described above for store_typed_address.
Here are some macros which architectures can define to indicate the relationship between
pointers and addresses. These have default definitions, appropriate for architectures on
which all pointers are simple unsigned byte addresses.
CORE_ADDR POINTER_TO_ADDRESS (struct type *type, char *buf )
[Target Macro]
Assume that buf holds a pointer of type type, in the appropriate format for the
current architecture. Return the byte address the pointer refers to.
This function may safely assume that type is either a pointer or a C++ reference type.
Chapter 9: Target Architecture Definition
void ADDRESS_TO_POINTER (struct type *type, char *buf,
CORE ADDR addr )
38
[Target Macro]
Store in buf a pointer of type type representing the address addr, in the appropriate
format for the current architecture.
This function may safely assume that type is either a pointer or a C++ reference type.
9.4 Address Classes
Sometimes information about different kinds of addresses is available via the debug information. For example, some programming environments define addresses of several different
sizes. If the debug information distinguishes these kinds of address classes through either
the size info (e.g, DW_AT_byte_size in DWARF 2) or through an explicit address class attribute (e.g, DW_AT_address_class in DWARF 2), the following macros should be defined
in order to disambiguate these types within gdb as well as provide the added information
to a gdb user when printing type expressions.
int ADDRESS_CLASS_TYPE_FLAGS (int byte_size, int
dwarf2_addr_class )
[Target Macro]
Returns the type flags needed to construct a pointer type whose size is byte size and
whose address class is dwarf2 addr class. This function is normally called from within
a symbol reader. See ‘dwarf2read.c’.
char *ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (int type_flags )
[Target Macro]
Given the type flags representing an address class qualifier, return its name.
int ADDRESS_CLASS_NAME_to_TYPE_FLAGS (int name, int
[Target Macro]
*vartype flags ptr)
Given an address qualifier name, set the int refererenced by type flags ptr to the
type flags for that address class qualifier.
Since the need for address classes is rather rare, none of the address class macros defined
by default. Predicate macros are provided to detect when they are defined.
Consider a hypothetical architecture in which addresses are normally 32-bits wide, but
16-bit addresses are also supported. Furthermore, suppose that the DWARF 2 information
for this architecture simply uses a DW_AT_byte_size value of 2 to indicate the use of one of
these "short" pointers. The following functions could be defined to implement the address
class macros:
somearch_address_class_type_flags (int byte_size,
int dwarf2_addr_class)
{
if (byte_size == 2)
return TYPE_FLAG_ADDRESS_CLASS_1;
else
return 0;
}
static char *
somearch_address_class_type_flags_to_name (int type_flags)
{
if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
return "short";
Chapter 9: Target Architecture Definition
39
else
return NULL;
}
int
somearch_address_class_name_to_type_flags (char *name,
int *type_flags_ptr)
{
if (strcmp (name, "short") == 0)
{
*type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
return 1;
}
else
return 0;
}
The qualifier @short is used in gdb’s type expressions to indicate the presence of one of
these "short" pointers. E.g, if the debug information indicates that short_ptr_var is one
of these short pointers, gdb might show the following behavior:
(gdb) ptype short_ptr_var
type = int * @short
9.5 Raw and Virtual Register Representations
Maintainer note: This section is pretty much obsolete. The functionality described here has
largely been replaced by pseudo-registers and the mechanisms described in Chapter 9 [Using
Different Register and Memory Data Representations], page 34. See also Bug Tracking
Database and ARI Index for more up-to-date information.
Some architectures use one representation for a value when it lives in a register, but
use a different representation when it lives in memory. In gdb’s terminology, the raw
representation is the one used in the target registers, and the virtual representation is the
one used in memory, and within gdb struct value objects.
Maintainer note: Notice that the same mechanism is being used to both convert a register
to a struct value and alternative register forms.
For almost all data types on almost all architectures, the virtual and raw representations
are identical, and no special handling is needed. However, they do occasionally differ. For
example:
• The x86 architecture supports an 80-bit long double type. However, when we store
those values in memory, they occupy twelve bytes: the floating-point number occupies
the first ten, and the final two bytes are unused. This keeps the values aligned on fourbyte boundaries, allowing more efficient access. Thus, the x86 80-bit floating-point
type is the raw representation, and the twelve-byte loosely-packed arrangement is the
virtual representation.
• Some 64-bit MIPS targets present 32-bit registers to gdb as 64-bit registers, with
garbage in their upper bits. gdb ignores the top 32 bits. Thus, the 64-bit form,
with garbage in the upper 32 bits, is the raw representation, and the trimmed 32-bit
representation is the virtual representation.
In general, the raw representation is determined by the architecture, or gdb’s interface
to the architecture, while the virtual representation can be chosen for gdb’s convenience.
Chapter 9: Target Architecture Definition
40
gdb’s register file, registers, holds the register contents in raw format, and the gdb
remote protocol transmits register values in raw format.
Your architecture may define the following macros to request conversions between the
raw and virtual format:
int REGISTER_CONVERTIBLE (int reg )
[Target Macro]
Return non-zero if register number reg’s value needs different raw and virtual formats.
You should not use REGISTER_CONVERT_TO_VIRTUAL for a register unless this macro
returns a non-zero value for that register.
int DEPRECATED_REGISTER_RAW_SIZE (int reg )
[Target Macro]
The size of register number reg’s raw value. This is the number of bytes the register
will occupy in registers, or in a gdb remote protocol packet.
int DEPRECATED_REGISTER_VIRTUAL_SIZE (int reg )
[Target Macro]
The size of register number reg’s value, in its virtual format. This is the size a struct
value’s buffer will have, holding that register’s value.
struct type *DEPRECATED REGISTER VIRTUAL TYPE (int
reg )
[Target Macro]
This is the type of the virtual representation of register number reg. Note that there
is no need for a macro giving a type for the register’s raw form; once the register’s
value has been obtained, gdb always uses the virtual form.
void REGISTER_CONVERT_TO_VIRTUAL (int reg, struct type *type,
char *from, char *to )
[Target Macro]
Convert the value of register number reg to type, which should always be DEPRECATED_
REGISTER_VIRTUAL_TYPE (reg ). The buffer at from holds the register’s value in raw
format; the macro should convert the value to virtual format, and place it at to.
Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
their reg and type arguments in different orders.
You should only use REGISTER_CONVERT_TO_VIRTUAL with registers for which the
REGISTER_CONVERTIBLE macro returns a non-zero value.
void REGISTER_CONVERT_TO_RAW (struct type *type, int reg, char
*from, char *to )
[Target Macro]
Convert the value of register number reg to type, which should always be DEPRECATED_
REGISTER_VIRTUAL_TYPE (reg ). The buffer at from holds the register’s value in raw
format; the macro should convert the value to virtual format, and place it at to.
Note that REGISTER CONVERT TO VIRTUAL and REGISTER CONVERT TO RAW
take their reg and type arguments in different orders.
9.6 Using Different Register and Memory Data
Representations
Maintainer’s note: The way GDB manipulates registers is undergoing significant change.
Many of the macros and functions refered to in this section are likely to be subject to further
Chapter 9: Target Architecture Definition
41
revision. See A.R. Index and Bug Tracking Database for further information. cagney/200205-06.
Some architectures can represent a data object in a register using a form that is different
to the objects more normal memory representation. For example:
• The Alpha architecture can represent 32 bit integer values in floating-point registers.
• The x86 architecture supports 80-bit floating-point registers. The long double data
type occupies 96 bits in memory but only 80 bits when stored in a register.
In general, the register representation of a data type is determined by the architecture,
or gdb’s interface to the architecture, while the memory representation is determined by
the Application Binary Interface.
For almost all data types on almost all architectures, the two representations are identical, and no special handling is needed. However, they do occasionally differ. Your architecture may define the following macros to request conversions between the register and
memory representations of a data type:
int CONVERT_REGISTER_P (int reg )
[Target Macro]
Return non-zero if the representation of a data value stored in this register may be
different to the representation of that same data value when stored in memory.
When non-zero, the macros REGISTER_TO_VALUE and VALUE_TO_REGISTER are used
to perform any necessary conversion.
void REGISTER_TO_VALUE (int reg, struct type *type, char *from,
char *to )
[Target Macro]
Convert the value of register number reg to a data object of type type. The buffer at
from holds the register’s value in raw format; the converted value should be placed in
the buffer at to.
Note that REGISTER_TO_VALUE and VALUE_TO_REGISTER take their reg and type arguments in different orders.
You should only use REGISTER_TO_VALUE with registers for which the CONVERT_
REGISTER_P macro returns a non-zero value.
void VALUE_TO_REGISTER (struct type *type, int reg, char *from,
char *to )
[Target Macro]
Convert a data value of type type to register number reg’ raw format.
Note that REGISTER_TO_VALUE and VALUE_TO_REGISTER take their reg and type arguments in different orders.
You should only use VALUE_TO_REGISTER with registers for which the CONVERT_
REGISTER_P macro returns a non-zero value.
void REGISTER_CONVERT_TO_TYPE (int regnum, struct type *type,
char *buf )
See ‘mips-tdep.c’. It does not do what you want.
9.7 Frame Interpretation
[Target Macro]
Chapter 9: Target Architecture Definition
42
9.8 Inferior Call Setup
9.9 Compiler Characteristics
9.10 Target Conditionals
This section describes the macros that you can use to define the target machine.
ADDR_BITS_REMOVE (addr)
If a raw machine instruction address includes any bits that are not really part
of the address, then define this macro to expand into an expression that zeroes
those bits in addr. This is only used for addresses of instructions, and even
then not in all contexts.
For example, the two low-order bits of the PC on the Hewlett-Packard PA
2.0 architecture contain the privilege level of the corresponding instruction.
Since instructions must always be aligned on four-byte boundaries, the processor masks out these bits to generate the actual address of the instruction.
ADDR BITS REMOVE should filter out these bits with an expression such as
((addr) & ~3).
ADDRESS_CLASS_NAME_TO_TYPE_FLAGS (name, type_flags_ptr )
If name is a valid address class qualifier name, set the int referenced by
type flags ptr to the mask representing the qualifier and return 1. If name
is not a valid address class qualifier name, return 0.
The value for type flags ptr should be one of TYPE_FLAG_ADDRESS_CLASS_1,
TYPE_FLAG_ADDRESS_CLASS_2, or possibly some combination of these values
or’d together. See Chapter 9 [Address Classes], page 34.
ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P ()
Predicate which indicates whether ADDRESS_CLASS_NAME_TO_TYPE_FLAGS has
been defined.
ADDRESS_CLASS_TYPE_FLAGS (byte_size, dwarf2_addr_class )
Given a pointers byte size (as described by the debug information) and the possible DW_AT_address_class value, return the type flags used by gdb to represent
this address class. The value returned should be one of TYPE_FLAG_ADDRESS_
CLASS_1, TYPE_FLAG_ADDRESS_CLASS_2, or possibly some combination of these
values or’d together. See Chapter 9 [Address Classes], page 34.
ADDRESS_CLASS_TYPE_FLAGS_P ()
Predicate which indicates whether ADDRESS_CLASS_TYPE_FLAGS has been defined.
ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (type_flags )
Return the name of the address class qualifier associated with the type flags
given by type flags.
ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P ()
Predicate which indicates whether ADDRESS_CLASS_TYPE_FLAGS_TO_NAME has
been defined. See Chapter 9 [Address Classes], page 34.
Chapter 9: Target Architecture Definition
43
ADDRESS_TO_POINTER (type, buf, addr )
Store in buf a pointer of type type representing the address addr, in the appropriate format for the current architecture. This macro may safely assume
that type is either a pointer or a C++ reference type. See Chapter 9 [Pointers
Are Not Always Addresses], page 34.
BELIEVE_PCC_PROMOTION
Define if the compiler promotes a short or char parameter to an int, but still
reports the parameter as its original type, rather than the promoted type.
BITS_BIG_ENDIAN
Define this if the numbering of bits in the targets does not match the endianness
of the target byte order. A value of 1 means that the bits are numbered in a
big-endian bit order, 0 means little-endian.
BREAKPOINT
This is the character array initializer for the bit pattern to put into memory
where a breakpoint is set. Although it’s common to use a trap instruction for
a breakpoint, it’s not required; for instance, the bit pattern could be an invalid
instruction. The breakpoint must be no longer than the shortest instruction of
the architecture.
BREAKPOINT has been deprecated in favor of BREAKPOINT_FROM_PC.
BIG_BREAKPOINT
LITTLE_BREAKPOINT
Similar to BREAKPOINT, but used for bi-endian targets.
BIG_BREAKPOINT and LITTLE_BREAKPOINT have been deprecated in favor of
BREAKPOINT_FROM_PC.
DEPRECATED_REMOTE_BREAKPOINT
DEPRECATED_LITTLE_REMOTE_BREAKPOINT
DEPRECATED_BIG_REMOTE_BREAKPOINT
Specify the breakpoint instruction sequence for a remote target. DEPRECATED_
REMOTE_BREAKPOINT, DEPRECATED_BIG_REMOTE_BREAKPOINT and DEPRECATED_
LITTLE_REMOTE_BREAKPOINT have been deprecated in favor of BREAKPOINT_
FROM_PC (see [BREAKPOINT FROM PC], page 43).
BREAKPOINT_FROM_PC (pcptr, lenptr )
Use the program counter to determine the contents and size of a breakpoint
instruction. It returns a pointer to a string of bytes that encode a breakpoint
instruction, stores the length of the string to *lenptr , and adjusts the program counter (if necessary) to point to the actual memory location where the
breakpoint should be inserted.
Although it is common to use a trap instruction for a breakpoint, it’s not
required; for instance, the bit pattern could be an invalid instruction. The
breakpoint must be no longer than the shortest instruction of the architecture.
Replaces all the other BREAKPOINT macros.
Chapter 9: Target Architecture Definition
44
MEMORY_INSERT_BREAKPOINT (bp_tgt )
MEMORY_REMOVE_BREAKPOINT (bp_tgt )
Insert or remove memory based breakpoints. Reasonable defaults (default_
memory_insert_breakpoint
and
default_memory_remove_breakpoint
respectively) have been provided so that it is not necessary to define
these for most architectures.
Architectures which may want to define
MEMORY_INSERT_BREAKPOINT and MEMORY_REMOVE_BREAKPOINT will likely have
instructions that are oddly sized or are not stored in a conventional manner.
It may also be desirable (from an efficiency standpoint) to define custom breakpoint insertion and removal routines if BREAKPOINT_FROM_PC needs to read the
target’s memory for some reason.
ADJUST_BREAKPOINT_ADDRESS (address )
Given an address at which a breakpoint is desired, return a breakpoint address
adjusted to account for architectural constraints on breakpoint placement. This
method is not needed by most targets.
The FR-V target (see ‘frv-tdep.c’) requires this method. The FR-V is a
VLIW architecture in which a number of RISC-like instructions are grouped
(packed) together into an aggregate instruction or instruction bundle. When
the processor executes one of these bundles, the component instructions are
executed in parallel.
In the course of optimization, the compiler may group instructions from distinct source statements into the same bundle. The line number information
associated with one of the latter statements will likely refer to some instruction other than the first one in the bundle. So, if the user attempts to place a
breakpoint on one of these latter statements, gdb must be careful to not place
the break instruction on any instruction other than the first one in the bundle.
(Remember though that the instructions within a bundle execute in parallel,
so the first instruction is the instruction at the lowest address and has nothing
to do with execution order.)
The FR-V’s ADJUST_BREAKPOINT_ADDRESS method will adjust a breakpoint’s
address by scanning backwards for the beginning of the bundle, returning the
address of the bundle.
Since the adjustment of a breakpoint may significantly alter a user’s expectation, gdb prints a warning when an adjusted breakpoint is initially set and each
time that that breakpoint is hit.
CALL_DUMMY_LOCATION
See the file ‘inferior.h’.
This method has been replaced by push_dummy_code (see [push dummy code],
page 53).
CANNOT_FETCH_REGISTER (regno )
A C expression that should be nonzero if regno cannot be fetched from an
inferior process. This is only relevant if FETCH_INFERIOR_REGISTERS is not
defined.
Chapter 9: Target Architecture Definition
45
CANNOT_STORE_REGISTER (regno )
A C expression that should be nonzero if regno should not be written to the
target. This is often the case for program counters, status words, and other
special registers. If this is not defined, gdb will assume that all registers may
be written.
int CONVERT_REGISTER_P(regnum )
Return non-zero if register regnum can represent data values in a non-standard
form. See Chapter 9 [Using Different Register and Memory Data Representations], page 34.
DECR_PC_AFTER_BREAK
Define this to be the amount by which to decrement the PC after the program
encounters a breakpoint. This is often the number of bytes in BREAKPOINT,
though not always. For most targets this value will be 0.
DISABLE_UNSETTABLE_BREAK (addr )
If defined, this should evaluate to 1 if addr is in a shared library in which
breakpoints cannot be set and so should be disabled.
PRINT_FLOAT_INFO()
If defined, then the ‘info float’ command will print information about the
processor’s floating point unit.
print_registers_info (gdbarch, frame, regnum, all )
If defined, pretty print the value of the register regnum for the specified frame.
If the value of regnum is -1, pretty print either all registers (all is non zero) or
a select subset of registers (all is zero).
The default method prints one register per line, and if all is zero omits floatingpoint registers.
PRINT_VECTOR_INFO()
If defined, then the ‘info vector’ command will call this function to print
information about the processor’s vector unit.
By default, the ‘info vector’ command will print all vector registers (the register’s type having the vector attribute).
DWARF_REG_TO_REGNUM
Convert DWARF register number into gdb regnum. If not defined, no conversion will be performed.
DWARF2_REG_TO_REGNUM
Convert DWARF2 register number into gdb regnum. If not defined, no conversion will be performed.
ECOFF_REG_TO_REGNUM
Convert ECOFF register number into gdb regnum. If not defined, no conversion
will be performed.
END_OF_TEXT_DEFAULT
This is an expression that should designate the end of the text section.
Chapter 9: Target Architecture Definition
46
EXTRACT_RETURN_VALUE(type, regbuf, valbuf )
Define this to extract a function’s return value of type type from the raw register
state regbuf and copy that, in virtual format, into valbuf.
This method has been deprecated in favour of gdbarch_return_value (see
[gdbarch return value], page 53).
DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS(regbuf )
When defined, extract from the array regbuf (containing the raw register state)
the CORE_ADDR at which a function should return its structure value.
See [gdbarch return value], page 53.
DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P()
Predicate for DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS.
DEPRECATED_FP_REGNUM
If the virtual frame pointer is kept in a register, then define this macro to be
the number (greater than or equal to zero) of that register.
This should only need to be defined if DEPRECATED_TARGET_READ_FP is not
defined.
DEPRECATED_FRAMELESS_FUNCTION_INVOCATION(fi )
Define this to an expression that returns 1 if the function invocation represented
by fi does not have a stack frame associated with it. Otherwise return 0.
frame_align (address )
Define this to adjust address so that it meets the alignment requirements for
the start of a new stack frame. A stack frame’s alignment requirements are
typically stronger than a target processors stack alignment requirements (see
[DEPRECATED STACK ALIGN], page 54).
This function is used to ensure that, when creating a dummy frame, both the
initial stack pointer and (if needed) the address of the return value are correctly
aligned.
Unlike DEPRECATED_STACK_ALIGN, this function always adjusts the address in
the direction of stack growth.
By default, no frame based stack alignment is performed.
int frame_red_zone_size
The number of bytes, beyond the innermost-stack-address, reserved by the abi.
A function is permitted to use this scratch area (instead of allocating extra
stack space).
When performing an inferior function call, to ensure that it does not modify this
area, gdb adjusts the innermost-stack-address by frame red zone size bytes
before pushing parameters onto the stack.
By default, zero bytes are allocated. The value must be aligned (see
[frame align], page 46).
The amd64 (nee x86-64) abi documentation refers to the red zone when describing this scratch area.
DEPRECATED_FRAME_CHAIN(frame )
Given frame, return a pointer to the calling frame.
Chapter 9: Target Architecture Definition
47
DEPRECATED_FRAME_CHAIN_VALID(chain, thisframe )
Define this to be an expression that returns zero if the given frame is an outermost frame, with no caller, and nonzero otherwise. Most normal situations can
be handled without defining this macro, including NULL chain pointers, dummy
frames, and frames whose PC values are inside the startup file (e.g. ‘crt0.o’),
inside main, or inside _start.
DEPRECATED_FRAME_INIT_SAVED_REGS(frame )
See ‘frame.h’. Determines the address of all registers in the current stack frame
storing each in frame->saved_regs. Space for frame->saved_regs shall be
allocated by DEPRECATED_FRAME_INIT_SAVED_REGS using frame_saved_regs_
zalloc.
FRAME_FIND_SAVED_REGS is deprecated.
FRAME_NUM_ARGS (fi )
For the frame described by fi return the number of arguments that are being
passed. If the number of arguments is not known, return -1.
DEPRECATED_FRAME_SAVED_PC(frame )
Given frame, return the pc saved there. This is the return address.
This method is deprecated. See [unwind pc], page 47.
CORE_ADDR unwind_pc (struct frame_info *this_frame )
Return the instruction address, in this frame’s caller, at which execution will
resume after this frame returns. This is commonly refered to as the return
address.
The implementation, which must be frame agnostic (work with any frame), is
typically no more than:
ULONGEST pc;
frame_unwind_unsigned_register (this_frame, D10V_PC_REGNUM, &pc);
return d10v_make_iaddr (pc);
See [DEPRECATED FRAME SAVED PC], page 47, which this method replaces.
CORE_ADDR unwind_sp (struct frame_info *this_frame )
Return the frame’s inner most stack address. This is commonly refered to as
the frame’s stack pointer.
The implementation, which must be frame agnostic (work with any frame), is
typically no more than:
ULONGEST sp;
frame_unwind_unsigned_register (this_frame, D10V_SP_REGNUM, &sp);
return d10v_make_daddr (sp);
See [TARGET READ SP], page 56, which this method replaces.
FUNCTION_EPILOGUE_SIZE
For some COFF targets, the x_sym.x_misc.x_fsize field of the function end
symbol is 0. For such targets, you must define FUNCTION_EPILOGUE_SIZE to
expand into the standard size of a function’s epilogue.
Chapter 9: Target Architecture Definition
48
DEPRECATED_FUNCTION_START_OFFSET
An integer, giving the offset in bytes from a function’s address (as used in
the values of symbols, function pointers, etc.), and the function’s first genuine
instruction.
This is zero on almost all machines: the function’s address is usually the address of its first instruction. However, on the VAX, for example, each function
starts with two bytes containing a bitmask indicating which registers to save
upon entry to the function. The VAX call instructions check this value, and
save the appropriate registers automatically. Thus, since the offset from the
function’s address to its first instruction is two bytes, DEPRECATED_FUNCTION_
START_OFFSET would be 2 on the VAX.
GCC_COMPILED_FLAG_SYMBOL
GCC2_COMPILED_FLAG_SYMBOL
If defined, these are the names of the symbols that gdb will look for to detect
that GCC compiled the file. The default symbols are gcc_compiled. and
gcc2_compiled., respectively. (Currently only defined for the Delta 68.)
gdb_MULTI_ARCH
If defined and non-zero, enables support for multiple architectures within gdb.
This support can be enabled at two levels. At level one, only definitions for
previously undefined macros are provided; at level two, a multi-arch definition
of all architecture dependent macros will be defined.
gdb_TARGET_IS_HPPA
This determines whether horrible kludge code in ‘dbxread.c’ and
‘partial-stab.h’ is used to mangle multiple-symbol-table files from HPPA’s.
This should all be ripped out, and a scheme like ‘elfread.c’ used instead.
GET_LONGJMP_TARGET
For most machines, this is a target-dependent parameter. On the DECstation and the Iris, this is a native-dependent parameter, since the header file
‘setjmp.h’ is needed to define it.
This macro determines the target PC address that longjmp will jump to, assuming that we have just stopped at a longjmp breakpoint. It takes a CORE_ADDR *
as argument, and stores the target PC value through this pointer. It examines
the current state of the machine as needed.
DEPRECATED_GET_SAVED_REGISTER
Define this if you need to supply your own definition for the function
DEPRECATED_GET_SAVED_REGISTER.
DEPRECATED_IBM6000_TARGET
Shows that we are configured for an IBM RS/6000 system. This conditional
should be eliminated (FIXME) and replaced by feature-specific macros. It was
introduced in a haste and we are repenting at leisure.
I386_USE_GENERIC_WATCHPOINTS
An x86-based target can define this to use the generic x86 watchpoint support;
see Chapter 3 [Algorithms], page 2.
Chapter 9: Target Architecture Definition
49
SYMBOLS_CAN_START_WITH_DOLLAR
Some systems have routines whose names start with ‘$’. Giving this macro a
non-zero value tells gdb’s expression parser to check for such routines when
parsing tokens that begin with ‘$’.
On HP-UX, certain system routines (millicode) have names beginning with ‘$’
or ‘$$’. For example, $$dyncall is a millicode routine that handles inter-space
procedure calls on PA-RISC.
DEPRECATED_INIT_EXTRA_FRAME_INFO (fromleaf, frame )
If additional information about the frame is required this should be stored in
frame->extra_info. Space for frame->extra_info is allocated using frame_
extra_info_zalloc.
DEPRECATED_INIT_FRAME_PC (fromleaf, prev )
This is a C statement that sets the pc of the frame pointed to by prev. [By
default...]
INNER_THAN (lhs, rhs )
Returns non-zero if stack address lhs is inner than (nearer to the stack top) stack
address rhs. Define this as lhs < rhs if the target’s stack grows downward in
memory, or lhs > rsh if the stack grows upward.
gdbarch_in_function_epilogue_p (gdbarch, pc )
Returns non-zero if the given pc is in the epilogue of a function. The epilogue
of a function is defined as the part of a function where the stack frame of the
function already has been destroyed up to the final ‘return from function call’
instruction.
DEPRECATED_SIGTRAMP_START (pc )
DEPRECATED_SIGTRAMP_END (pc )
Define these to be the start and end address of the sigtramp for the given
pc. On machines where the address is just a compile time constant, the macro
expansion will typically just ignore the supplied pc.
IN_SOLIB_CALL_TRAMPOLINE (pc, name )
Define this to evaluate to nonzero if the program is stopped in the trampoline
that connects to a shared library.
IN_SOLIB_RETURN_TRAMPOLINE (pc, name )
Define this to evaluate to nonzero if the program is stopped in the trampoline
that returns from a shared library.
IN_SOLIB_DYNSYM_RESOLVE_CODE (pc )
Define this to evaluate to nonzero if the program is stopped in the dynamic
linker.
SKIP_SOLIB_RESOLVER (pc )
Define this to evaluate to the (nonzero) address at which execution should
continue to get past the dynamic linker’s symbol resolution function. A zero
value indicates that it is not important or necessary to set a breakpoint to get
through the dynamic linker and that single stepping will suffice.
Chapter 9: Target Architecture Definition
50
INTEGER_TO_ADDRESS (type, buf )
Define this when the architecture needs to handle non-pointer to address conversions specially. Converts that value to an address according to the current
architectures conventions.
Pragmatics: When the user copies a well defined expression from their source
code and passes it, as a parameter, to gdb’s print command, they should
get the same value as would have been computed by the target program. Any
deviation from this rule can cause major confusion and annoyance, and needs to
be justified carefully. In other words, gdb doesn’t really have the freedom to do
these conversions in clever and useful ways. It has, however, been pointed out
that users aren’t complaining about how gdb casts integers to pointers; they are
complaining that they can’t take an address from a disassembly listing and give
it to x/i. Adding an architecture method like INTEGER_TO_ADDRESS certainly
makes it possible for gdb to “get it right” in all circumstances.
See Chapter 9 [Pointers Are Not Always Addresses], page 34.
NO_HIF_SUPPORT
(Specific to the a29k.)
POINTER_TO_ADDRESS (type, buf )
Assume that buf holds a pointer of type type, in the appropriate format for
the current architecture. Return the byte address the pointer refers to. See
Chapter 9 [Pointers Are Not Always Addresses], page 34.
REGISTER_CONVERTIBLE (reg )
Return non-zero if reg uses different raw and virtual formats. See Chapter 9
[Raw and Virtual Register Representations], page 34.
REGISTER_TO_VALUE(regnum, type, from, to )
Convert the raw contents of register regnum into a value of type type. See Chapter 9 [Using Different Register and Memory Data Representations], page 34.
DEPRECATED_REGISTER_RAW_SIZE (reg )
Return the raw size of reg; defaults to the size of the register’s virtual type.
See Chapter 9 [Raw and Virtual Register Representations], page 34.
register_reggroup_p (gdbarch, regnum, reggroup )
Return non-zero if register regnum is a member of the register group reggroup.
By default, registers are grouped as follows:
float_reggroup
Any register with a valid name and a floating-point type.
vector_reggroup
Any register with a valid name and a vector type.
general_reggroup
Any register with a valid name and a type other than vector or
floating-point. ‘float_reggroup’.
Chapter 9: Target Architecture Definition
51
save_reggroup
restore_reggroup
all_reggroup
Any register with a valid name.
DEPRECATED_REGISTER_VIRTUAL_SIZE (reg )
Return the virtual size of reg; defaults to the size of the register’s virtual type.
Return the virtual size of reg. See Chapter 9 [Raw and Virtual Register Representations], page 34.
DEPRECATED_REGISTER_VIRTUAL_TYPE (reg )
Return the virtual type of reg. See Chapter 9 [Raw and Virtual Register Representations], page 34.
struct type *register_type (gdbarch, reg )
If defined, return the type of register reg. This function superseeds DEPRECATED_
REGISTER_VIRTUAL_TYPE. See Chapter 9 [Raw and Virtual Register Representations], page 34.
REGISTER_CONVERT_TO_VIRTUAL(reg, type, from, to )
Convert the value of register reg from its raw form to its virtual form. See
Chapter 9 [Raw and Virtual Register Representations], page 34.
REGISTER_CONVERT_TO_RAW(type, reg, from, to )
Convert the value of register reg from its virtual form to its raw form. See
Chapter 9 [Raw and Virtual Register Representations], page 34.
const struct regset *regset_from_core_section (struct gdbarch * gdbarch, const
char * sect_name, size_t sect_size )
Return the appropriate register set for a core file section with name sect name
and size sect size.
SOFTWARE_SINGLE_STEP_P()
Define this as 1 if the target does not have a hardware single-step mechanism.
The macro SOFTWARE_SINGLE_STEP must also be defined.
SOFTWARE_SINGLE_STEP(signal, insert_breapoints_p )
A function that inserts or removes (depending on insert breapoints p) breakpoints at each possible destinations of the next instruction. See ‘sparc-tdep.c’
and ‘rs6000-tdep.c’ for examples.
SOFUN_ADDRESS_MAYBE_MISSING
Somebody clever observed that, the more actual addresses you have in the
debug information, the more time the linker has to spend relocating them. So
whenever there’s some other way the debugger could find the address it needs,
you should omit it from the debug info, to make linking faster.
SOFUN_ADDRESS_MAYBE_MISSING indicates that a particular set of hacks of this
sort are in use, affecting N_SO and N_FUN entries in stabs-format debugging information. N_SO stabs mark the beginning and ending addresses of compilation
units in the text segment. N_FUN stabs mark the starts and ends of functions.
SOFUN_ADDRESS_MAYBE_MISSING means two things:
Chapter 9: Target Architecture Definition
52
• N_FUN stabs have an address of zero. Instead, you should find the addresses
where the function starts by taking the function name from the stab, and
then looking that up in the minsyms (the linker/assembler symbol table).
In other words, the stab has the name, and the linker/assembler symbol
table is the only place that carries the address.
• N_SO stabs have an address of zero, too. You just look at the N_FUN stabs
that appear before and after the N_SO stab, and guess the starting and
ending addresses of the compilation unit from them.
PC_LOAD_SEGMENT
If defined, print information about the load segment for the program counter.
(Defined only for the RS/6000.)
PC_REGNUM
If the program counter is kept in a register, then define this macro to be the
number (greater than or equal to zero) of that register.
This should only need to be defined if TARGET_READ_PC and TARGET_WRITE_PC
are not defined.
PARM_BOUNDARY
If non-zero, round arguments to a boundary of this many bits before pushing
them on the stack.
stabs_argument_has_addr (gdbarch, type )
Define this to return nonzero if a function argument of type type is passed by
reference instead of value.
This method replaces DEPRECATED_REG_STRUCT_HAS_ADDR (see [DEPRECATED REG STRUCT HAS ADDR], page 53).
PROCESS_LINENUMBER_HOOK
A hook defined for XCOFF reading.
PROLOGUE_FIRSTLINE_OVERLAP
(Only used in unsupported Convex configuration.)
PS_REGNUM
If defined, this is the number of the processor status register. (This definition
is only used in generic code when parsing "$ps".)
DEPRECATED_POP_FRAME
If defined, used by frame_pop to remove a stack frame. This method has been
superseeded by generic code.
push_dummy_call (gdbarch, function, regcache, pc_addr, nargs, args, sp,
struct_return, struct_addr )
Define this to push the dummy frame’s call to the inferior function onto the
stack. In addition to pushing nargs, the code should push struct addr (when
struct return), and the return address (bp addr).
function is a pointer to a struct value; on architectures that use function
descriptors, this contains the function descriptor value.
Returns the updated top-of-stack pointer.
Chapter 9: Target Architecture Definition
53
This method replaces DEPRECATED_PUSH_ARGUMENTS.
CORE_ADDR push_dummy_code (gdbarch, sp, funaddr, using_gcc, args, nargs,
value_type, real_pc, bp_addr )
Given a stack based call dummy, push the instruction sequence (including space
for a breakpoint) to which the called function should return.
Set bp addr to the address at which the breakpoint instruction should be inserted, real pc to the resume address when starting the call sequence, and
return the updated inner-most stack address.
By default, the stack is grown sufficient to hold a frame-aligned (see
[frame align], page 46) breakpoint, bp addr is set to the address reserved for
that breakpoint, and real pc set to funaddr.
This method replaces CALL_DUMMY_LOCATION, DEPRECATED_REGISTER_SIZE.
REGISTER_NAME(i )
Return the name of register i as a string. May return NULL or NUL to indicate
that register i is not valid.
DEPRECATED_REG_STRUCT_HAS_ADDR (gcc_p, type )
Define this to return 1 if the given type will be passed by pointer rather than
directly.
This method has been replaced by stabs_argument_has_addr (see
[stabs argument has addr], page 52).
SAVE_DUMMY_FRAME_TOS (sp )
Used in ‘call_function_by_hand’ to notify the target dependent code of the
top-of-stack value that will be passed to the the inferior code. This is the value
of the SP after both the dummy frame and space for parameters/results have
been allocated on the stack. See [unwind dummy id], page 56.
SDB_REG_TO_REGNUM
Define this to convert sdb register numbers into gdb regnums. If not defined,
no conversion will be done.
enum return_value_convention gdbarch_return_value (struct gdbarch *gdbarch,
struct type *valtype, struct regcache *regcache, void *readbuf, const void
*writebuf )
Given a function with a return-value of type rettype, return which return-value
convention that function would use.
gdb currently recognizes two function return-value conventions: RETURN_
VALUE_REGISTER_CONVENTION where the return value is found in registers;
and RETURN_VALUE_STRUCT_CONVENTION where the return value is found in
memory and the address of that memory location is passed in as the function’s
first parameter.
If the register convention is being used, and writebuf is non-NULL, also copy
the return-value in writebuf into regcache.
If the register convention is being used, and readbuf is non-NULL, also copy
the return value from regcache into readbuf (regcache contains a copy of the
registers from the just returned function).
Chapter 9: Target Architecture Definition
54
See [DEPRECATED EXTRACT STRUCT VALUE ADDRESS], page 46, for
a description of how return-values that use the struct convention are handled.
Maintainer note: This method replaces separate predicate, extract, store methods. By having only one method, the logic needed to determine the return-value
convention need only be implemented in one place. If gdb were written in an oo
language, this method would instead return an object that knew how to perform
the register return-value extract and store.
Maintainer note: This method does not take a gcc p parameter, and such a
parameter should not be added. If an architecture that requires per-compiler
or per-function information be identified, then the replacement of rettype with
struct value function should be persued.
Maintainer note: The regcache parameter limits this methods to the inner most
frame. While replacing regcache with a struct frame_info frame parameter
would remove that limitation there has yet to be a demonstrated need for such
a change.
SKIP_PERMANENT_BREAKPOINT
Advance the inferior’s PC past a permanent breakpoint. gdb normally steps
over a breakpoint by removing it, stepping one instruction, and re-inserting the
breakpoint. However, permanent breakpoints are hardwired into the inferior,
and can’t be removed, so this strategy doesn’t work. Calling SKIP_PERMANENT_
BREAKPOINT adjusts the processor’s state so that execution will resume just after
the breakpoint. This macro does the right thing even when the breakpoint is
in the delay slot of a branch or jump.
SKIP_PROLOGUE (pc )
A C expression that returns the address of the “real” code beyond the function
entry prologue found at pc.
SKIP_TRAMPOLINE_CODE (pc )
If the target machine has trampoline code that sits between callers and the
functions being called, then define this macro to return a new PC that is at the
start of the real function.
SP_REGNUM
If the stack-pointer is kept in a register, then define this macro to be the number
(greater than or equal to zero) of that register, or -1 if there is no such register.
STAB_REG_TO_REGNUM
Define this to convert stab register numbers (as gotten from ‘r’ declarations)
into gdb regnums. If not defined, no conversion will be done.
DEPRECATED_STACK_ALIGN (addr )
Define this to increase addr so that it meets the alignment requirements for the
processor’s stack.
Unlike [frame align], page 46, this function always adjusts addr upwards.
By default, no stack alignment is performed.
STEP_SKIPS_DELAY (addr )
Define this to return true if the address is of an instruction with a delay slot. If
a breakpoint has been placed in the instruction’s delay slot, gdb will single-step
Chapter 9: Target Architecture Definition
55
over that instruction before resuming normally. Currently only defined for the
Mips.
STORE_RETURN_VALUE (type, regcache, valbuf )
A C expression that writes the function return value, found in valbuf, into the
regcache. type is the type of the value that is to be returned.
This method has been deprecated in favour of gdbarch_return_value (see
[gdbarch return value], page 53).
SYMBOL_RELOADING_DEFAULT
The default value of the “symbol-reloading” variable. (Never defined in current
sources.)
TARGET_CHAR_BIT
Number of bits in a char; defaults to 8.
TARGET_CHAR_SIGNED
Non-zero if char is normally signed on this architecture; zero if it should be
unsigned.
The ISO C standard requires the compiler to treat char as equivalent to either
signed char or unsigned char; any character in the standard execution set
is supposed to be positive. Most compilers treat char as signed, but char is
unsigned on the IBM S/390, RS6000, and PowerPC targets.
TARGET_COMPLEX_BIT
Number of bits in a complex number; defaults to 2 * TARGET_FLOAT_BIT.
At present this macro is not used.
TARGET_DOUBLE_BIT
Number of bits in a double float; defaults to 8 * TARGET_CHAR_BIT.
TARGET_DOUBLE_COMPLEX_BIT
Number of bits in a double complex; defaults to 2 * TARGET_DOUBLE_BIT.
At present this macro is not used.
TARGET_FLOAT_BIT
Number of bits in a float; defaults to 4 * TARGET_CHAR_BIT.
TARGET_INT_BIT
Number of bits in an integer; defaults to 4 * TARGET_CHAR_BIT.
TARGET_LONG_BIT
Number of bits in a long integer; defaults to 4 * TARGET_CHAR_BIT.
TARGET_LONG_DOUBLE_BIT
Number of bits in a long double float; defaults to 2 * TARGET_DOUBLE_BIT.
TARGET_LONG_LONG_BIT
Number of bits in a long long integer; defaults to 2 * TARGET_LONG_BIT.
TARGET_PTR_BIT
Number of bits in a pointer; defaults to TARGET_INT_BIT.
TARGET_SHORT_BIT
Number of bits in a short integer; defaults to 2 * TARGET_CHAR_BIT.
Chapter 9: Target Architecture Definition
56
TARGET_READ_PC
TARGET_WRITE_PC (val, pid )
TARGET_READ_SP
TARGET_READ_FP
These change the behavior of read_pc, write_pc, and read_sp. For most
targets, these may be left undefined. gdb will call the read and write register
functions with the relevant _REGNUM argument.
These macros are useful when a target keeps one of these registers in a hard to
get at place; for example, part in a segment register and part in an ordinary
register.
See [unwind sp], page 47, which replaces TARGET_READ_SP.
TARGET_VIRTUAL_FRAME_POINTER(pc, regp, offsetp )
Returns a (register, offset) pair representing the virtual frame pointer in
use at the code address pc. If virtual frame pointers are not used, a default
definition simply returns DEPRECATED_FP_REGNUM, with an offset of zero.
TARGET_HAS_HARDWARE_WATCHPOINTS
If non-zero, the target has support for hardware-assisted watchpoints. See
Chapter 3 [Algorithms], page 2, for more details and other related macros.
TARGET_PRINT_INSN (addr, info )
This is the function used by gdb to print an assembly instruction. It prints
the instruction at address addr in debugged memory and returns the length of
the instruction, in bytes. If a target doesn’t define its own printing routine, it
defaults to an accessor function for the global pointer deprecated_tm_print_
insn. This usually points to a function in the opcodes library (see Chapter 12
[Opcodes], page 65). info is a structure (of type disassemble_info) defined
in ‘include/dis-asm.h’ used to pass information to the instruction decoding
routine.
struct frame_id unwind_dummy_id (struct frame_info *frame )
Given frame return a struct frame_id that uniquely identifies an inferior
function call’s dummy frame. The value returned must match the dummy
frame stack value previously saved using SAVE_DUMMY_FRAME_TOS.
See
[SAVE DUMMY FRAME TOS], page 53.
DEPRECATED_USE_STRUCT_CONVENTION (gcc_p, type )
If defined, this must be an expression that is nonzero if a value of the given type
being returned from a function must have space allocated for it on the stack.
gcc p is true if the function being considered is known to have been compiled
by GCC; this is helpful for systems where GCC is known to use different calling
convention than other compilers.
This method has been deprecated in favour of gdbarch_return_value (see
[gdbarch return value], page 53).
VALUE_TO_REGISTER(type, regnum, from, to )
Convert a value of type type into the raw contents of register regnum’s. See
Chapter 9 [Using Different Register and Memory Data Representations],
page 34.
Chapter 9: Target Architecture Definition
57
VARIABLES_INSIDE_BLOCK (desc, gcc_p )
For dbx-style debugging information, if the compiler puts variable declarations
inside LBRAC/RBRAC blocks, this should be defined to be nonzero. desc is
the value of n_desc from the N_RBRAC symbol, and gcc p is true if gdb has noticed the presence of either the GCC_COMPILED_SYMBOL or the GCC2_COMPILED_
SYMBOL. By default, this is 0.
OS9K_VARIABLES_INSIDE_BLOCK (desc, gcc_p )
Similarly, for OS/9000. Defaults to 1.
Motorola M68K target conditionals.
BPT_VECTOR
Define this to be the 4-bit location of the breakpoint trap vector. If not defined,
it will default to 0xf.
REMOTE_BPT_VECTOR
Defaults to 1.
NAME_OF_MALLOC
A string containing the name of the function to call in order to allocate some
memory in the inferior. The default value is "malloc".
9.11 Adding a New Target
The following files add a target to gdb:
‘gdb/config/arch /ttt.mt’
Contains a Makefile fragment specific to this target. Specifies what object files
are needed for target ttt, by defining ‘TDEPFILES=...’ and ‘TDEPLIBS=...’.
Also specifies the header file which describes ttt, by defining ‘TM_FILE=
tm-ttt.h’.
You can also define ‘TM_CFLAGS’, ‘TM_CLIBS’, ‘TM_CDEPS’, but these are now
deprecated, replaced by autoconf, and may go away in future versions of gdb.
‘gdb/ttt-tdep.c’
Contains any miscellaneous code required for this target machine. On some
machines it doesn’t exist at all. Sometimes the macros in ‘tm-ttt.h’ become
very complicated, so they are implemented as functions here instead, and the
macro is simply defined to call the function. This is vastly preferable, since it
is easier to understand and debug.
‘gdb/arch-tdep.c’
‘gdb/arch-tdep.h’
This often exists to describe the basic layout of the target machine’s processor
chip (registers, stack, etc.). If used, it is included by ‘ttt-tdep.h’. It can be
shared among many targets that use the same processor.
‘gdb/config/arch /tm-ttt.h’
(‘tm.h’ is a link to this file, created by configure). Contains macro definitions
about the target machine’s registers, stack frame format and instructions.
New targets do not need this file and should not create it.
Chapter 9: Target Architecture Definition
58
‘gdb/config/arch /tm-arch.h’
This often exists to describe the basic layout of the target machine’s processor
chip (registers, stack, etc.). If used, it is included by ‘tm-ttt.h’. It can be
shared among many targets that use the same processor.
New targets do not need this file and should not create it.
If you are adding a new operating system for an existing CPU chip, add a
‘config/tm-os.h’ file that describes the operating system facilities that are unusual (extra
symbol table info; the breakpoint instruction needed; etc.). Then write a ‘arch /tm-os.h’
that just #includes ‘tm-arch.h’ and ‘config/tm-os.h’.
9.12 Converting an existing Target Architecture to Multiarch
This section describes the current accepted best practice for converting an existing target
architecture to the multi-arch framework.
The process consists of generating, testing, posting and committing a sequence of
patches. Each patch must contain a single change, for instance:
• Directly convert a group of functions into macros (the conversion does not change the
behavior of any of the functions).
• Replace a non-multi-arch with a multi-arch mechanism (e.g., FRAME_INFO).
• Enable multi-arch level one.
• Delete one or more files.
There isn’t a size limit on a patch, however, a developer is strongly encouraged to keep the
patch size down.
Since each patch is well defined, and since each change has been tested and shows no
regressions, the patches are considered fairly obvious. Such patches, when submitted by
developers listed in the ‘MAINTAINERS’ file, do not need approval. Occasional steps in the
process may be more complicated and less clear. The developer is expected to use their
judgment and is encouraged to seek advice as needed.
9.12.1 Preparation
The first step is to establish control. Build (with ‘-Werror’ enabled) and test the target so
that there is a baseline against which the debugger can be compared.
At no stage can the test results regress or gdb stop compiling with ‘-Werror’.
9.12.2 Add the multi-arch initialization code
The objective of this step is to establish the basic multi-arch framework. It involves
• The addition of a arch _gdbarch_init function4 that creates the architecture:
static struct gdbarch *
d10v_gdbarch_init (info, arches)
struct gdbarch_info info;
struct gdbarch_list *arches;
4
The above is from the original example and uses K&R C. gdb has since converted to ISO C but lets
ignore that.
Chapter 9: Target Architecture Definition
59
{
struct gdbarch *gdbarch;
/* there is only one d10v architecture */
if (arches != NULL)
return arches->gdbarch;
gdbarch = gdbarch_alloc (&info, NULL);
return gdbarch;
}
• A per-architecture dump function to print any architecture specific information:
static void
mips_dump_tdep (struct gdbarch *current_gdbarch,
struct ui_file *file)
{
... code to print architecture specific info ...
}
• A change to _initialize_arch _tdep to register this new architecture:
void
_initialize_mips_tdep (void)
{
gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
mips_dump_tdep);
• Add the macro GDB_MULTI_ARCH, defined as 0 (zero), to the file
‘config/arch /tm-arch.h’.
9.12.3 Update multi-arch incompatible mechanisms
Some mechanisms do not work with multi-arch. They include:
FRAME_FIND_SAVED_REGS
Replaced with DEPRECATED_FRAME_INIT_SAVED_REGS
At this stage you could also consider converting the macros into functions.
9.12.4 Prepare for multi-arch level to one
Temporally set GDB_MULTI_ARCH to GDB_MULTI_ARCH_PARTIAL and then build and start
gdb (the change should not be committed). gdb may not build, and once built, it may die
with an internal error listing the architecture methods that must be provided.
Fix any build problems (patch(es)).
Convert all the architecture methods listed, which are only macros, into functions
(patch(es)).
Update arch _gdbarch_init to set all the missing architecture methods and wrap the
corresponding macros in #if !GDB_MULTI_ARCH (patch(es)).
9.12.5 Set multi-arch level one
Change the value of GDB_MULTI_ARCH to GDB MULTI ARCH PARTIAL (a single patch).
Any problems with throwing “the switch” should have been fixed already.
9.12.6 Convert remaining macros
Suggest converting macros into functions (and setting the corresponding architecture
method) in small batches.
Chapter 10: Target Vector Definition
60
9.12.7 Set multi-arch level to two
This should go smoothly.
9.12.8 Delete the TM file
The ‘tm-arch.h’ can be deleted. ‘arch.mt’ and ‘configure.in’ updated.
10 Target Vector Definition
The target vector defines the interface between gdb’s abstract handling of target systems,
and the nitty-gritty code that actually exercises control over a process or a serial port. gdb
includes some 30-40 different target vectors; however, each configuration of gdb includes
only a few of them.
10.1 File Targets
Both executables and core files have target vectors.
10.2 Standard Protocol and Remote Stubs
gdb’s file ‘remote.c’ talks a serial protocol to code that runs in the target system. gdb
provides several sample stubs that can be integrated into target programs or operating
systems for this purpose; they are named ‘*-stub.c’.
The gdb user’s manual describes how to put such a stub into your target code. What
follows is a discussion of integrating the SPARC stub into a complicated operating system
(rather than a simple program), by Stu Grossman, the author of this stub.
The trap handling code in the stub assumes the following upon entry to trap_low:
1. %l1 and %l2 contain pc and npc respectively at the time of the trap;
2. traps are disabled;
3. you are in the correct trap window.
As long as your trap handler can guarantee those conditions, then there is no reason why you shouldn’t be able to “share” traps with the stub. The stub has no requirement that it be jumped to directly from the hardware trap vector. That is why it calls
exceptionHandler(), which is provided by the external environment. For instance, this
could set up the hardware traps to actually execute code which calls the stub first, and then
transfers to its own trap handler.
For the most point, there probably won’t be much of an issue with “sharing” traps, as
the traps we use are usually not used by the kernel, and often indicate unrecoverable error
conditions. Anyway, this is all controlled by a table, and is trivial to modify. The most
important trap for us is for ta 1. Without that, we can’t single step or do breakpoints.
Everything else is unnecessary for the proper operation of the debugger/stub.
From reading the stub, it’s probably not obvious how breakpoints work. They are simply
done by deposit/examine operations from gdb.
10.3 ROM Monitor Interface
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10.4 Custom Protocols
10.5 Transport Layer
10.6 Builtin Simulator
11 Native Debugging
Several files control gdb’s configuration for native support:
‘gdb/config/arch /xyz.mh’
Specifies Makefile fragments needed by a native configuration on machine
xyz. In particular, this lists the required native-dependent object files, by
defining ‘NATDEPFILES=...’. Also specifies the header file which describes
native support on xyz, by defining ‘NAT_FILE= nm-xyz.h’. You can also
define ‘NAT_CFLAGS’, ‘NAT_ADD_FILES’, ‘NAT_CLIBS’, ‘NAT_CDEPS’, etc.; see
‘Makefile.in’.
Maintainer’s note: The ‘.mh’ suffix is because this file originally contained
‘Makefile’ fragments for hosting gdb on machine xyz. While the file is no
longer used for this purpose, the ‘.mh’ suffix remains. Perhaps someone will
eventually rename these fragments so that they have a ‘.mn’ suffix.
‘gdb/config/arch /nm-xyz.h’
(‘nm.h’ is a link to this file, created by configure). Contains C macro definitions describing the native system environment, such as child process control
and core file support.
‘gdb/xyz-nat.c’
Contains any miscellaneous C code required for this native support of this
machine. On some machines it doesn’t exist at all.
There are some “generic” versions of routines that can be used by various systems.
These can be customized in various ways by macros defined in your ‘nm-xyz.h’ file. If these
routines work for the xyz host, you can just include the generic file’s name (with ‘.o’, not
‘.c’) in NATDEPFILES.
Otherwise, if your machine needs custom support routines, you will need to write routines
that perform the same functions as the generic file. Put them into ‘xyz-nat.c’, and put
‘xyz-nat.o’ into NATDEPFILES.
‘inftarg.c’
This contains the target ops vector that supports Unix child processes on systems which use ptrace and wait to control the child.
‘procfs.c’
This contains the target ops vector that supports Unix child processes on systems which use /proc to control the child.
‘fork-child.c’
This does the low-level grunge that uses Unix system calls to do a “fork and
exec” to start up a child process.
Chapter 11: Native Debugging
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‘infptrace.c’
This is the low level interface to inferior processes for systems using the Unix
ptrace call in a vanilla way.
11.1 Native core file Support
‘core-aout.c::fetch_core_registers()’
Support for reading registers out of a core file.
This routine calls
register_addr(), see below. Now that BFD is used to read core files,
virtually all machines should use core-aout.c, and should just provide
fetch_core_registers in xyz -nat.c (or REGISTER_U_ADDR in nm-xyz.h).
‘core-aout.c::register_addr()’
If your nm-xyz.h file defines the macro REGISTER_U_ADDR(addr, blockend,
regno), it should be defined to set addr to the offset within the ‘user’ struct of
gdb register number regno. blockend is the offset within the “upage” of u.u_
ar0. If REGISTER_U_ADDR is defined, ‘core-aout.c’ will define the register_
addr() function and use the macro in it. If you do not define REGISTER_U_ADDR,
but you are using the standard fetch_core_registers(), you will need to
define your own version of register_addr(), put it into your xyz -nat.c file,
and be sure xyz -nat.o is in the NATDEPFILES list. If you have your own fetch_
core_registers(), you may not need a separate register_addr(). Many
custom fetch_core_registers() implementations simply locate the registers
themselves.
When making gdb run native on a new operating system, to make it possible to debug
core files, you will need to either write specific code for parsing your OS’s core files, or
customize ‘bfd/trad-core.c’. First, use whatever #include files your machine uses to
define the struct of registers that is accessible (possibly in the u-area) in a core file (rather
than ‘machine/reg.h’), and an include file that defines whatever header exists on a core
file (e.g., the u-area or a struct core). Then modify trad_unix_core_file_p to use
these values to set up the section information for the data segment, stack segment, any
other segments in the core file (perhaps shared library contents or control information),
“registers” segment, and if there are two discontiguous sets of registers (e.g., integer and
float), the “reg2” segment. This section information basically delimits areas in the core file
in a standard way, which the section-reading routines in BFD know how to seek around in.
Then back in gdb, you need a matching routine called fetch_core_registers. If you
can use the generic one, it’s in ‘core-aout.c’; if not, it’s in your ‘xyz-nat.c’ file. It will
be passed a char pointer to the entire “registers” segment, its length, and a zero; or a char
pointer to the entire “regs2” segment, its length, and a 2. The routine should suck out the
supplied register values and install them into gdb’s “registers” array.
If your system uses ‘/proc’ to control processes, and uses ELF format core files, then
you may be able to use the same routines for reading the registers out of processes and out
of core files.
11.2 ptrace
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11.3 /proc
11.4 win32
11.5 shared libraries
11.6 Native Conditionals
When gdb is configured and compiled, various macros are defined or left undefined, to
control compilation when the host and target systems are the same. These macros should
be defined (or left undefined) in ‘nm-system.h’.
CHILD_PREPARE_TO_STORE
If the machine stores all registers at once in the child process, then define this
to ensure that all values are correct. This usually entails a read from the child.
[Note that this is incorrectly defined in ‘xm-system.h’ files currently.]
FETCH_INFERIOR_REGISTERS
Define this if the native-dependent code will provide its own routines fetch_
inferior_registers and store_inferior_registers in ‘host-nat.c’. If
this symbol is not defined, and ‘infptrace.c’ is included in this configuration, the default routines in ‘infptrace.c’ are used for these functions.
FP0_REGNUM
This macro is normally defined to be the number of the first floating point
register, if the machine has such registers. As such, it would appear only in
target-specific code. However, ‘/proc’ support uses this to decide whether floats
are in use on this target.
GET_LONGJMP_TARGET
For most machines, this is a target-dependent parameter. On the DECstation
and the Iris, this is a native-dependent parameter, since ‘setjmp.h’ is needed
to define it.
This macro determines the target PC address that longjmp will jump to, assuming that we have just stopped at a longjmp breakpoint. It takes a CORE_ADDR *
as argument, and stores the target PC value through this pointer. It examines
the current state of the machine as needed.
I386_USE_GENERIC_WATCHPOINTS
An x86-based machine can define this to use the generic x86 watchpoint support;
see Chapter 3 [Algorithms], page 2.
KERNEL_U_ADDR
Define this to the address of the u structure (the “user struct”, also known as
the “u-page”) in kernel virtual memory. gdb needs to know this so that it can
subtract this address from absolute addresses in the upage, that are obtained
via ptrace or from core files. On systems that don’t need this value, set it to
zero.
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KERNEL_U_ADDR_HPUX
Define this to cause gdb to determine the address of u at runtime, by using
HP-style nlist on the kernel’s image in the root directory.
ONE_PROCESS_WRITETEXT
Define this to be able to, when a breakpoint insertion fails, warn the user that
another process may be running with the same executable.
PROC_NAME_FMT
Defines the format for the name of a ‘/proc’ device. Should be defined in ‘nm.h’
only in order to override the default definition in ‘procfs.c’.
PTRACE_ARG3_TYPE
The type of the third argument to the ptrace system call, if it exists and is
different from int.
REGISTER_U_ADDR
Defines the offset of the registers in the “u area”.
SHELL_COMMAND_CONCAT
If defined, is a string to prefix on the shell command used to start the inferior.
SHELL_FILE
If defined, this is the name of the shell to use to run the inferior. Defaults to
"/bin/sh".
SOLIB_ADD (filename, from_tty, targ, readsyms )
Define this to expand into an expression that will cause the symbols in filename
to be added to gdb’s symbol table. If readsyms is zero symbols are not read
but any necessary low level processing for filename is still done.
SOLIB_CREATE_INFERIOR_HOOK
Define this to expand into any shared-library-relocation code that you want to
be run just after the child process has been forked.
START_INFERIOR_TRAPS_EXPECTED
When starting an inferior, gdb normally expects to trap twice; once when the
shell execs, and once when the program itself execs. If the actual number of
traps is something other than 2, then define this macro to expand into the
number expected.
USE_PROC_FS
This determines whether small routines in ‘*-tdep.c’, which translate register
values between gdb’s internal representation and the ‘/proc’ representation,
are compiled.
U_REGS_OFFSET
This is the offset of the registers in the upage. It need only be defined if
the generic ptrace register access routines in ‘infptrace.c’ are being used
(that is, ‘infptrace.c’ is configured in, and FETCH_INFERIOR_REGISTERS is
not defined). If the default value from ‘infptrace.c’ is good enough, leave it
undefined.
Chapter 12: Support Libraries
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The default value means that u.u ar0 points to the location of the registers. I’m
guessing that #define U_REGS_OFFSET 0 means that u.u_ar0 is the location
of the registers.
CLEAR_SOLIB
See ‘objfiles.c’.
DEBUG_PTRACE
Define this to debug ptrace calls.
12 Support Libraries
12.1 BFD
BFD provides support for gdb in several ways:
identifying executable and core files
BFD will identify a variety of file types, including a.out, coff, and several variants thereof, as well as several kinds of core files.
access to sections of files
BFD parses the file headers to determine the names, virtual addresses, sizes,
and file locations of all the various named sections in files (such as the text
section or the data section). gdb simply calls BFD to read or write section x
at byte offset y for length z.
specialized core file support
BFD provides routines to determine the failing command name stored in a core
file, the signal with which the program failed, and whether a core file matches
(i.e. could be a core dump of) a particular executable file.
locating the symbol information
gdb uses an internal interface of BFD to determine where to find the symbol
information in an executable file or symbol-file. gdb itself handles the reading
of symbols, since BFD does not “understand” debug symbols, but gdb uses
BFD’s cached information to find the symbols, string table, etc.
12.2 opcodes
The opcodes library provides gdb’s disassembler. (It’s a separate library because it’s also
used in binutils, for ‘objdump’).
12.3 readline
12.4 mmalloc
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12.5 libiberty
The libiberty library provides a set of functions and features that integrate and improve
on functionality found in modern operating systems. Broadly speaking, such features can
be divided into three groups: supplemental functions (functions that may be missing in
some environments and operating systems), replacement functions (providing a uniform
and easier to use interface for commonly used standard functions), and extensions (which
provide additional functionality beyond standard functions).
gdb uses various features provided by the libiberty library, for instance the C++ demangler, the IEEE floating format support functions, the input options parser ‘getopt’, the
‘obstack’ extension, and other functions.
12.5.1 obstacks in gdb
The obstack mechanism provides a convenient way to allocate and free chunks of memory.
Each obstack is a pool of memory that is managed like a stack. Objects (of any nature, size
and alignment) are allocated and freed in a LIFO fashion on an obstack (see libiberty’s
documenatation for a more detailed explanation of obstacks).
The most noticeable use of the obstacks in gdb is in object files. There is an obstack
associated with each internal representation of an object file. Lots of things get allocated
on these obstacks: dictionary entries, blocks, blockvectors, symbols, minimal symbols,
types, vectors of fundamental types, class fields of types, object files section lists, object
files section offets lists, line tables, symbol tables, partial symbol tables, string tables,
symbol table private data, macros tables, debug information sections and entries, import
and export lists (som), unwind information (hppa), dwarf2 location expressions data. Plus
various strings such as directory names strings, debug format strings, names of types.
An essential and convenient property of all data on obstacks is that memory for it
gets allocated (with obstack_alloc) at various times during a debugging sesssion, but it is
released all at once using the obstack_free function. The obstack_free function takes a
pointer to where in the stack it must start the deletion from (much like the cleanup chains
have a pointer to where to start the cleanups). Because of the stack like structure of the
obstacks, this allows to free only a top portion of the obstack. There are a few instances
in gdb where such thing happens. Calls to obstack_free are done after some local data
is allocated to the obstack. Only the local data is deleted from the obstack. Of course
this assumes that nothing between the obstack_alloc and the obstack_free allocates
anything else on the same obstack. For this reason it is best and safest to use temporary
obstacks.
Releasing the whole obstack is also not safe per se. It is safe only under the condition
that we know the obstacks memory is no longer needed. In gdb we get rid of the obstacks
only when we get rid of the whole objfile(s), for instance upon reading a new symbol file.
12.6 gnu-regex
Regex conditionals.
C_ALLOCA
NFAILURES
RE_NREGS
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SIGN_EXTEND_CHAR
SWITCH_ENUM_BUG
SYNTAX_TABLE
Sword
sparc
12.7 include
13 Coding
This chapter covers topics that are lower-level than the major algorithms of gdb.
13.1 Cleanups
Cleanups are a structured way to deal with things that need to be done later.
When your code does something (e.g., xmalloc some memory, or open a file) that needs
to be undone later (e.g., xfree the memory or close the file), it can make a cleanup.
The cleanup will be done at some future point: when the command is finished and control
returns to the top level; when an error occurs and the stack is unwound; or when your code
decides it’s time to explicitly perform cleanups. Alternatively you can elect to discard the
cleanups you created.
Syntax:
struct cleanup *old_chain ;
Declare a variable which will hold a cleanup chain handle.
old_chain = make_cleanup (function, arg );
Make a cleanup which will cause function to be called with arg (a char *) later.
The result, old chain, is a handle that can later be passed to do_cleanups or
discard_cleanups. Unless you are going to call do_cleanups or discard_
cleanups, you can ignore the result from make_cleanup.
do_cleanups (old_chain );
Do all cleanups added to the chain since the corresponding make_cleanup call
was made.
discard_cleanups (old_chain );
Same as do_cleanups except that it just removes the cleanups from the chain
and does not call the specified functions.
Cleanups are implemented as a chain. The handle returned by make_cleanups includes
the cleanup passed to the call and any later cleanups appended to the chain (but not yet
discarded or performed). E.g.:
make_cleanup (a, 0);
{
struct cleanup *old = make_cleanup (b, 0);
make_cleanup (c, 0)
...
do_cleanups (old);
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}
will call c() and b() but will not call a(). The cleanup that calls a() will remain in the
cleanup chain, and will be done later unless otherwise discarded.
Your function should explicitly do or discard the cleanups it creates. Failing to do
this leads to non-deterministic behavior since the caller will arbitrarily do or discard your
functions cleanups. This need leads to two common cleanup styles.
The first style is try/finally. Before it exits, your code-block calls do_cleanups with the
old cleanup chain and thus ensures that your code-block’s cleanups are always performed.
For instance, the following code-segment avoids a memory leak problem (even when error
is called and a forced stack unwind occurs) by ensuring that the xfree will always be called:
struct cleanup *old = make_cleanup (null_cleanup, 0);
data = xmalloc (sizeof blah);
make_cleanup (xfree, data);
... blah blah ...
do_cleanups (old);
The second style is try/except. Before it exits, your code-block calls discard_cleanups
with the old cleanup chain and thus ensures that any created cleanups are not performed.
For instance, the following code segment, ensures that the file will be closed but only if
there is an error:
FILE *file = fopen ("afile", "r");
struct cleanup *old = make_cleanup (close_file, file);
... blah blah ...
discard_cleanups (old);
return file;
Some functions, e.g., fputs_filtered() or error(), specify that they “should not be
called when cleanups are not in place”. This means that any actions you need to reverse
in the case of an error or interruption must be on the cleanup chain before you call these
functions, since they might never return to your code (they ‘longjmp’ instead).
13.2 Per-architecture module data
The multi-arch framework includes a mechanism for adding module specific per-architecture
data-pointers to the struct gdbarch architecture object.
A module registers one or more per-architecture data-pointers using:
struct gdbarch_data *gdbarch data register pre init
(gdbarch data pre init ftype *pre_init )
[Function]
pre init is used to, on-demand, allocate an initial value for a per-architecture datapointer using the architecture’s obstack (passed in as a parameter). Since pre init can
be called during architecture creation, it is not parameterized with the architecture.
and must not call modules that use per-architecture data.
struct gdbarch_data *gdbarch data register post init
(gdbarch data post init ftype *post_init )
[Function]
post init is used to obtain an initial value for a per-architecture data-pointer after.
Since post init is always called after architecture creation, it both receives the fully
initialized architecture and is free to call modules that use per-architecture data (care
needs to be taken to ensure that those other modules do not try to call back to this
module as that will create in cycles in the initialization call graph).
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These functions return a struct gdbarch_data that is used to identify the
per-architecture data-pointer added for that module.
The per-architecture data-pointer is accessed using the function:
void *gdbarch_data (struct gdbarch *gdbarch, struct gdbarch data
*data_handle )
[Function]
Given the architecture arch and module data handle data handle (returned by
gdbarch_data_register_pre_init or gdbarch_data_register_post_init), this
function returns the current value of the per-architecture data-pointer. If the data
pointer is NULL, it is first initialized by calling the corresponding pre init or post init
method.
The examples below assume the following definitions:
struct nozel { int total; };
static struct gdbarch_data *nozel_handle;
A module can extend the architecture vector, adding additional per-architecture data,
using the pre init method. The module’s per-architecture data is then initialized during
architecture creation.
In the below, the module’s per-architecture nozel is added. An architecture can specify
its nozel by calling set_gdbarch_nozel from gdbarch_init.
static void *
nozel_pre_init (struct obstack *obstack)
{
struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel);
return data;
}
extern void
set_gdbarch_nozel (struct gdbarch *gdbarch, int total)
{
struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
data->total = nozel;
}
A module can on-demand create architecture dependant data structures using post_
init.
In the below, the nozel’s total is computed on-demand by nozel_post_init using information obtained from the architecture.
static void *
nozel_post_init (struct gdbarch *gdbarch)
{
struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel);
nozel->total = gdbarch... (gdbarch);
return data;
}
extern int
nozel_total (struct gdbarch *gdbarch)
{
struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
return data->total;
}
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13.3 Wrapping Output Lines
Output that goes through printf_filtered or fputs_filtered or fputs_demangled
needs only to have calls to wrap_here added in places that would be good breaking points.
The utility routines will take care of actually wrapping if the line width is exceeded.
The argument to wrap_here is an indentation string which is printed only if the line
breaks there. This argument is saved away and used later. It must remain valid until
the next call to wrap_here or until a newline has been printed through the *_filtered
functions. Don’t pass in a local variable and then return!
It is usually best to call wrap_here after printing a comma or space. If you call it before
printing a space, make sure that your indentation properly accounts for the leading space
that will print if the line wraps there.
Any function or set of functions that produce filtered output must finish by printing a
newline, to flush the wrap buffer, before switching to unfiltered (printf) output. Symbol
reading routines that print warnings are a good example.
13.4 gdb Coding Standards
gdb follows the GNU coding standards, as described in ‘etc/standards.texi’. This file is
also available for anonymous FTP from GNU archive sites. gdb takes a strict interpretation
of the standard; in general, when the GNU standard recommends a practice but does not
require it, gdb requires it.
gdb follows an additional set of coding standards specific to gdb, as described in the
following sections.
13.4.1 ISO C
gdb assumes an ISO/IEC 9899:1990 (a.k.a. ISO C90) compliant compiler.
gdb does not assume an ISO C or POSIX compliant C library.
13.4.2 Memory Management
gdb does not use the functions malloc, realloc, calloc, free and asprintf.
gdb uses the functions xmalloc, xrealloc and xcalloc when allocating memory. Unlike
malloc et.al. these functions do not return when the memory pool is empty. Instead, they
unwind the stack using cleanups. These functions return NULL when requested to allocate
a chunk of memory of size zero.
Pragmatics: By using these functions, the need to check every memory allocation is
removed. These functions provide portable behavior.
gdb does not use the function free.
gdb uses the function xfree to return memory to the memory pool. Consistent with
ISO-C, this function ignores a request to free a NULL pointer.
Pragmatics: On some systems free fails when passed a NULL pointer.
gdb can use the non-portable function alloca for the allocation of small temporary
values (such as strings).
Pragmatics: This function is very non-portable. Some systems restrict the memory being
allocated to no more than a few kilobytes.
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gdb uses the string function xstrdup and the print function xstrprintf.
Pragmatics: asprintf and strdup can fail. Print functions such as sprintf are very
prone to buffer overflow errors.
13.4.3 Compiler Warnings
With few exceptions,
developers should include the configuration option
‘--enable-gdb-build-warnings=,-Werror’ when building gdb.
The exceptions
are listed in the file ‘gdb/MAINTAINERS’.
This option causes gdb (when built using GCC) to be compiled with a carefully selected
list of compiler warning flags. Any warnings from those flags being treated as errors.
The current list of warning flags includes:
‘-Wimplicit’
Since gdb coding standard requires all functions to be declared using a prototype, the flag has the side effect of ensuring that prototyped functions are
always visible with out resorting to ‘-Wstrict-prototypes’.
‘-Wreturn-type’
Such code often appears to work except on instruction set architectures that
use register windows.
‘-Wcomment’
‘-Wtrigraphs’
‘-Wformat’
‘-Wformat-nonliteral’
Since gdb uses the format printf attribute on all printf like functions
these check not just printf calls but also calls to functions such as
fprintf_unfiltered.
‘-Wparentheses’
This warning includes uses of the assignment operator within an if statement.
‘-Wpointer-arith’
‘-Wuninitialized’
‘-Wunused-label’
This warning has the additional benefit of detecting the absence of the case
reserved word in a switch statement:
enum { FD_SCHEDULED, NOTHING_SCHEDULED } sched;
...
switch (sched)
{
case FD_SCHEDULED:
...;
break;
NOTHING_SCHEDULED:
...;
break;
}
‘-Wunused-function’
‘-Wno-pointer-sign’
In version 4.0, GCC began warning about pointer argument passing or assignment even when the source and destination differed only in signedness. How-
Chapter 13: Coding
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ever, most gdb code doesn’t distinguish carefully between char and unsigned
char. In early 2006 the gdb developers decided correcting these warnings
wasn’t worth the time it would take.
Pragmatics: Due to the way that gdb is implemented most functions have unused parameters. Consequently the warning ‘-Wunused-parameter’ is precluded from the list. The
macro ATTRIBUTE_UNUSED is not used as it leads to false negatives — it is not an error
to have ATTRIBUTE_UNUSED on a parameter that is being used. The options ‘-Wall’ and
‘-Wunused’ are also precluded because they both include ‘-Wunused-parameter’.
Pragmatics: gdb has not simply accepted the warnings enabled by ‘-Wall -Werror
-W...’. Instead it is selecting warnings when and where their benefits can be demonstrated.
13.4.4 Formatting
The standard GNU recommendations for formatting must be followed strictly.
A function declaration should not have its name in column zero. A function definition
should have its name in column zero.
/* Declaration */
static void foo (void);
/* Definition */
void
foo (void)
{
}
Pragmatics: This simplifies scripting.
‘^function-name’.
Function definitions can be found using
There must be a space between a function or macro name and the opening parenthesis
of its argument list (except for macro definitions, as required by C). There must not be a
space after an open paren/bracket or before a close paren/bracket.
While additional whitespace is generally helpful for reading, do not use more than one
blank line to separate blocks, and avoid adding whitespace after the end of a program line
(as of 1/99, some 600 lines had whitespace after the semicolon). Excess whitespace causes
difficulties for diff and patch utilities.
Pointers are declared using the traditional K&R C style:
void *foo;
and not:
void * foo;
void* foo;
13.4.5 Comments
The standard GNU requirements on comments must be followed strictly.
Block comments must appear in the following form, with no /*- or */-only lines, and no
leading *:
/* Wait for control to return from inferior to debugger. If inferior
gets a signal, we may decide to start it up again instead of
returning. That is why there is a loop in this function. When
this function actually returns it means the inferior should be left
stopped and gdb should read more commands. */
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(Note that this format is encouraged by Emacs; tabbing for a multi-line comment works
correctly, and M-q fills the block consistently.)
Put a blank line between the block comments preceding function or variable definitions,
and the definition itself.
In general, put function-body comments on lines by themselves, rather than trying to fit
them into the 20 characters left at the end of a line, since either the comment or the code
will inevitably get longer than will fit, and then somebody will have to move it anyhow.
13.4.6 C Usage
Code must not depend on the sizes of C data types, the format of the host’s floating point
numbers, the alignment of anything, or the order of evaluation of expressions.
Use functions freely. There are only a handful of compute-bound areas in gdb that
might be affected by the overhead of a function call, mainly in symbol reading. Most of
gdb’s performance is limited by the target interface (whether serial line or system call).
However, use functions with moderation. A thousand one-line functions are just as hard
to understand as a single thousand-line function.
Macros are bad, M’kay. (But if you have to use a macro, make sure that the macro
arguments are protected with parentheses.)
Declarations like ‘struct foo *’ should be used in preference to declarations like
‘typedef struct foo { ... } *foo_ptr’.
13.4.7 Function Prototypes
Prototypes must be used when both declaring and defining a function. Prototypes for gdb
functions must include both the argument type and name, with the name matching that
used in the actual function definition.
All external functions should have a declaration in a header file that callers include,
except for _initialize_* functions, which must be external so that ‘init.c’ construction
works, but shouldn’t be visible to random source files.
Where a source file needs a forward declaration of a static function, that declaration
must appear in a block near the top of the source file.
13.4.8 Internal Error Recovery
During its execution, gdb can encounter two types of errors. User errors and internal errors.
User errors include not only a user entering an incorrect command but also problems arising
from corrupt object files and system errors when interacting with the target. Internal errors
include situations where gdb has detected, at run time, a corrupt or erroneous situation.
When reporting an internal error, gdb uses internal_error and gdb_assert.
gdb must not call abort or assert.
Pragmatics: There is no internal_warning function. Either the code detected a user
error, recovered from it and issued a warning or the code failed to correctly recover from
the user error and issued an internal_error.
Chapter 13: Coding
74
13.4.9 File Names
Any file used when building the core of gdb must be in lower case. Any file used when
building the core of gdb must be 8.3 unique. These requirements apply to both source and
generated files.
Pragmatics: The core of gdb must be buildable on many platforms including DJGPP
and MacOS/HFS. Every time an unfriendly file is introduced to the build process both
‘Makefile.in’ and ‘configure.in’ need to be modified accordingly. Compare the convoluted conversion process needed to transform ‘COPYING’ into ‘copying.c’ with the conversion
needed to transform ‘version.in’ into ‘version.c’.
Any file non 8.3 compliant file (that is not used when building the core of gdb) must be
added to ‘gdb/config/djgpp/fnchange.lst’.
Pragmatics: This is clearly a compromise.
When gdb has a local version of a system header file (ex ‘string.h’) the file name based
on the POSIX header prefixed with ‘gdb_’ (‘gdb_string.h’). These headers should be
relatively independent: they should use only macros defined by ‘configure’, the compiler,
or the host; they should include only system headers; they should refer only to system types.
They may be shared between multiple programs, e.g. gdb and gdbserver.
For other files ‘-’ is used as the separator.
13.4.10 Include Files
A ‘.c’ file should include ‘defs.h’ first.
A ‘.c’ file should directly include the .h file of every declaration and/or definition it
directly refers to. It cannot rely on indirect inclusion.
A ‘.h’ file should directly include the .h file of every declaration and/or definition it
directly refers to. It cannot rely on indirect inclusion. Exception: The file ‘defs.h’ does
not need to be directly included.
An external declaration should only appear in one include file.
An external declaration should never appear in a .c file. Exception: a declaration for
the _initialize function that pacifies ‘-Wmissing-declaration’.
A typedef definition should only appear in one include file.
An opaque struct declaration can appear in multiple ‘.h’ files. Where possible, a ‘.h’
file should use an opaque struct declaration instead of an include.
All ‘.h’ files should be wrapped in:
#ifndef INCLUDE_FILE_NAME_H
#define INCLUDE_FILE_NAME_H
header body
#endif
13.4.11 Clean Design and Portable Implementation
In addition to getting the syntax right, there’s the little question of semantics. Some things
are done in certain ways in gdb because long experience has shown that the more obvious
ways caused various kinds of trouble.
You can’t assume the byte order of anything that comes from a target (including values,
object files, and instructions). Such things must be byte-swapped using SWAP_TARGET_AND_
HOST in gdb, or one of the swap routines defined in ‘bfd.h’, such as bfd_get_32.
Chapter 13: Coding
75
You can’t assume that you know what interface is being used to talk to the target system.
All references to the target must go through the current target_ops vector.
You can’t assume that the host and target machines are the same machine (except in
the “native” support modules). In particular, you can’t assume that the target machine’s
header files will be available on the host machine. Target code must bring along its own
header files – written from scratch or explicitly donated by their owner, to avoid copyright
problems.
Insertion of new #ifdef’s will be frowned upon. It’s much better to write the code
portably than to conditionalize it for various systems.
New #ifdef’s which test for specific compilers or manufacturers or operating systems are
unacceptable. All #ifdef’s should test for features. The information about which configurations contain which features should be segregated into the configuration files. Experience
has proven far too often that a feature unique to one particular system often creeps into
other systems; and that a conditional based on some predefined macro for your current system will become worthless over time, as new versions of your system come out that behave
differently with regard to this feature.
Adding code that handles specific architectures, operating systems, target interfaces, or
hosts, is not acceptable in generic code.
One particularly notorious area where system dependencies tend to creep in is handling
of file names. The mainline gdb code assumes Posix semantics of file names: absolute
file names begin with a forward slash ‘/’, slashes are used to separate leading directories,
case-sensitive file names. These assumptions are not necessarily true on non-Posix systems
such as MS-Windows. To avoid system-dependent code where you need to take apart or
construct a file name, use the following portable macros:
HAVE_DOS_BASED_FILE_SYSTEM
This preprocessing symbol is defined to a non-zero value on hosts whose filesystems belong to the MS-DOS/MS-Windows family. Use this symbol to write
conditional code which should only be compiled for such hosts.
IS_DIR_SEPARATOR (c )
Evaluates to a non-zero value if c is a directory separator character. On Unix
and GNU/Linux systems, only a slash ‘/’ is such a character, but on Windows,
both ‘/’ and ‘\’ will pass.
IS_ABSOLUTE_PATH (file )
Evaluates to a non-zero value if file is an absolute file name. For Unix and
GNU/Linux hosts, a name which begins with a slash ‘/’ is absolute. On DOS
and Windows, ‘d:/foo’ and ‘x:\bar’ are also absolute file names.
FILENAME_CMP (f1, f2 )
Calls a function which compares file names f1 and f2 as appropriate for the
underlying host filesystem. For Posix systems, this simply calls strcmp; on
case-insensitive filesystems it will call strcasecmp instead.
DIRNAME_SEPARATOR
Evaluates to a character which separates directories in PATH-style lists, typically
held in environment variables. This character is ‘:’ on Unix, ‘;’ on DOS and
Windows.
Chapter 14: Porting gdb
76
SLASH_STRING
This evaluates to a constant string you should use to produce an absolute
filename from leading directories and the file’s basename. SLASH_STRING is "/"
on most systems, but might be "\\" for some Windows-based ports.
In addition to using these macros, be sure to use portable library functions whenever
possible. For example, to extract a directory or a basename part from a file name, use the
dirname and basename library functions (available in libiberty for platforms which don’t
provide them), instead of searching for a slash with strrchr.
Another way to generalize gdb along a particular interface is with an attribute struct.
For example, gdb has been generalized to handle multiple kinds of remote interfaces—not
by #ifdefs everywhere, but by defining the target_ops structure and having a current
target (as well as a stack of targets below it, for memory references). Whenever something
needs to be done that depends on which remote interface we are using, a flag in the current
target ops structure is tested (e.g., target_has_stack), or a function is called through a
pointer in the current target ops structure. In this way, when a new remote interface is
added, only one module needs to be touched—the one that actually implements the new
remote interface. Other examples of attribute-structs are BFD access to multiple kinds of
object file formats, or gdb’s access to multiple source languages.
Please avoid duplicating code. For example, in gdb 3.x all the code interfacing between
ptrace and the rest of gdb was duplicated in ‘*-dep.c’, and so changing something was very
painful. In gdb 4.x, these have all been consolidated into ‘infptrace.c’. ‘infptrace.c’
can deal with variations between systems the same way any system-independent file would
(hooks, #if defined, etc.), and machines which are radically different don’t need to use
‘infptrace.c’ at all.
All debugging code must be controllable using the ‘set debug module ’ command. Do
not use printf to print trace messages. Use fprintf_unfiltered(gdb_stdlog, .... Do
not use #ifdef DEBUG.
14 Porting gdb
Most of the work in making gdb compile on a new machine is in specifying the configuration of the machine. This is done in a dizzying variety of header files and configuration
scripts, which we hope to make more sensible soon. Let’s say your new host is called
an xyz (e.g., ‘sun4’), and its full three-part configuration name is arch -xvend -xos (e.g.,
‘sparc-sun-sunos4’). In particular:
• In the top level directory, edit ‘config.sub’ and add arch, xvend, and xos to the lists
of supported architectures, vendors, and operating systems near the bottom of the file.
Also, add xyz as an alias that maps to arch -xvend -xos . You can test your changes
by running
./config.sub xyz
and
./config.sub arch -xvend -xos
which should both respond with arch -xvend -xos and no error messages.
You need to port BFD, if that hasn’t been done already. Porting BFD is beyond the
scope of this manual.
Chapter 15: Versions and Branches
77
• To configure gdb itself, edit ‘gdb/configure.host’ to recognize your system and
set gdb_host to xyz, and (unless your desired target is already available) also edit
‘gdb/configure.tgt’, setting gdb_target to something appropriate (for instance,
xyz).
Maintainer’s note: Work in progress. The file ‘gdb/configure.host’ originally needed
to be modified when either a new native target or a new host machine was being added
to gdb. Recent changes have removed this requirement. The file now only needs to be
modified when adding a new native configuration. This will likely changed again in the
future.
• Finally, you’ll need to specify and define gdb’s host-, native-, and target-dependent
‘.h’ and ‘.c’ files used for your configuration.
15 Versions and Branches
15.1 Versions
gdb’s version is determined by the file ‘gdb/version.in’ and takes one of the following
forms:
major.minor
major.minor.patchlevel
an official release (e.g., 6.2 or 6.2.1)
major.minor.patchlevel.YYYY MM DD
a snapshot taken at YYYY-MM-DD-gmt
6.1.90.20020304, or 6.1.0.20020308)
(e.g.,
6.1.50.20020302,
major.minor.patchlevel.YYYY MM DD-cvs
a cvs check out drawn on YYYY-MM-DD (e.g., 6.1.50.20020302-cvs,
6.1.90.20020304-cvs, or 6.1.0.20020308-cvs)
major.minor.patchlevel.YYYY MM DD (vendor)
a vendor specific release of gdb, that while based on
major.minor.patchlevel.YYYY MM DD, may include additional changes
gdb’s mainline uses the major and minor version numbers from the most recent release
branch, with a patchlevel of 50. At the time each new release branch is created, the
mainline’s major and minor version numbers are updated.
gdb’s release branch is similar. When the branch is cut, the patchlevel is changed from
50 to 90. As draft releases are drawn from the branch, the patchlevel is incremented. Once
the first release (major.minor) has been made, the patchlevel is set to 0 and updates have
an incremented patchlevel.
For snapshots, and cvs check outs, it is also possible to identify the cvs origin:
major.minor.50.YYYY MM DD
drawn from the head of mainline cvs (e.g., 6.1.50.20020302)
major.minor.90.YYYY MM DD
major.minor.91.YYYY MM DD . . .
drawn from a release branch prior to the release (e.g., 6.1.90.20020304)
Chapter 15: Versions and Branches
78
major.minor.0.YYYY MM DD
major.minor.1.YYYY MM DD . . .
drawn from a release branch after the release (e.g., 6.2.0.20020308)
If the previous gdb version is 6.1 and the current version is 6.2, then, substituting 6 for
major and 1 or 2 for minor, here’s an illustration of a typical sequence:
<HEAD>
|
6.1.50.20020302-cvs
|
+--------------------------.
|
<gdb_6_2-branch>
|
|
6.2.50.20020303-cvs
6.1.90 (draft #1)
|
|
6.2.50.20020304-cvs
6.1.90.20020304-cvs
|
|
6.2.50.20020305-cvs
6.1.91 (draft #2)
|
|
6.2.50.20020306-cvs
6.1.91.20020306-cvs
|
|
6.2.50.20020307-cvs
6.2 (release)
|
|
6.2.50.20020308-cvs
6.2.0.20020308-cvs
|
|
6.2.50.20020309-cvs
6.2.1 (update)
|
|
6.2.50.20020310-cvs
<branch closed>
|
6.2.50.20020311-cvs
|
+--------------------------.
|
<gdb_6_3-branch>
|
|
6.3.50.20020312-cvs
6.2.90 (draft #1)
|
|
15.2 Release Branches
gdb draws a release series (6.2, 6.2.1, . . . ) from a single release branch, and identifies that
branch using the cvs branch tags:
gdb_major _minor-YYYY MM DD-branchpoint
gdb_major _minor-branch
gdb_major _minor-YYYY MM DD-release
Pragmatics: To help identify the date at which a branch or release is made, both the
branchpoint and release tags include the date that they are cut (YYYY MM DD) in the tag.
The branch tag, denoting the head of the branch, does not need this.
15.3 Vendor Branches
To avoid version conflicts, vendors are expected to modify the file ‘gdb/version.in’ to
include a vendor unique alphabetic identifier (an official gdb release never uses alphabetic
characters in its version identifer). E.g., ‘6.2widgit2’, or ‘6.2 (Widgit Inc Patch 2)’.
Chapter 15: Versions and Branches
79
15.4 Experimental Branches
15.4.1 Guidelines
gdb permits the creation of branches, cut from the cvs repository, for experimental development. Branches make it possible for developers to share preliminary work, and maintainers
to examine significant new developments.
The following are a set of guidelines for creating such branches:
a branch has an owner
The owner can set further policy for a branch, but may not change the ground
rules. In particular, they can set a policy for commits (be it adding more
reviewers or deciding who can commit).
all commits are posted
All changes committed to a branch shall also be posted to the gdb patches
mailing list. While commentary on such changes are encouraged, people should
remember that the changes only apply to a branch.
all commits are covered by an assignment
This ensures that all changes belong to the Free Software Foundation, and
avoids the possibility that the branch may become contaminated.
a branch is focused
A focused branch has a single objective or goal, and does not contain unnecessary or irrelevant changes. Cleanups, where identified, being be pushed into
the mainline as soon as possible.
a branch tracks mainline
This keeps the level of divergence under control. It also keeps the pressure on
developers to push cleanups and other stuff into the mainline.
a branch shall contain the entire gdb module
The gdb module gdb should be specified when creating a branch (branches of
individual files should be avoided). See [Tags], page 79.
a branch shall be branded using ‘version.in’
The file ‘gdb/version.in’ shall be modified so that it identifies the branch
owner and branch name, e.g., ‘6.2.50.20030303_owner_name’ or ‘6.2 (Owner
Name)’.
15.4.2 Tags
To simplify the identification of gdb branches, the following branch tagging convention is
strongly recommended:
owner _name-YYYYMMDD-branchpoint
owner _name-YYYYMMDD-branch
The branch point and corresponding branch tag. YYYYMMDD is the date
that the branch was created. A branch is created using the sequence:
cvs rtag owner _name-YYYYMMDD-branchpoint gdb
cvs rtag -b -r owner _name-YYYYMMDD-branchpoint \
owner _name-YYYYMMDD-branch gdb
Chapter 17: Releasing gdb
80
owner _name-yyyymmdd-mergepoint
The tagged point, on the mainline, that was used when merging the branch on
yyyymmdd. To merge in all changes since the branch was cut, use a command
sequence like:
cvs rtag owner _name-yyyymmdd-mergepoint gdb
cvs update \
-jowner _name-YYYYMMDD-branchpoint
-jowner _name-yyyymmdd-mergepoint
Similar sequences can be used to just merge in changes since the last merge.
For further information on cvs, see Concurrent Versions System.
16 Start of New Year Procedure
At the start of each new year, the following actions should be performed:
• Rotate the ChangeLog file
The current ‘ChangeLog’ file should be renamed into ‘ChangeLog-YYYY’ where YYYY
is the year that has just passed. A new ‘ChangeLog’ file should be created, and its
contents should contain a reference to the previous ChangeLog. The following should
also be preserved at the end of the new ChangeLog, in order to provide the appropriate
settings when editing this file with Emacs:
Local Variables:
mode: change-log
left-margin: 8
fill-column: 74
version-control: never
End:
• Update the copyright year in the startup message
Update the copyright year in file ‘top.c’, function print_gdb_version.
17 Releasing gdb
17.1 Branch Commit Policy
The branch commit policy is pretty slack. gdb releases 5.0, 5.1 and 5.2 all used the below:
• The ‘gdb/MAINTAINERS’ file still holds.
• Don’t fix something on the branch unless/until it is also fixed in the trunk. If this isn’t
possible, mentioning it in the ‘gdb/PROBLEMS’ file is better than committing a hack.
• When considering a patch for the branch, suggested criteria include: Does it fix a build?
Does it fix the sequence break main; run when debugging a static binary?
• The further a change is from the core of gdb, the less likely the change will worry
anyone (e.g., target specific code).
• Only post a proposal to change the core of gdb after you’ve sent individual bribes to
all the people listed in the ‘MAINTAINERS’ file ;-)
Pragmatics: Provided updates are restricted to non-core functionality there is little chance
that a broken change will be fatal. This means that changes such as adding a new architectures or (within reason) support for a new host are considered acceptable.
Chapter 17: Releasing gdb
81
17.2 Obsoleting code
Before anything else, poke the other developers (and around the source code) to see if there
is anything that can be removed from gdb (an old target, an unused file).
Obsolete code is identified by adding an OBSOLETE prefix to every line. Doing this means
that it is easy to identify something that has been obsoleted when greping through the
sources.
The process is done in stages — this is mainly to ensure that the wider gdb community
has a reasonable opportunity to respond. Remember, everything on the Internet takes a
week.
1. Post the proposal on the GDB mailing list Creating a bug report to track the task’s
state, is also highly recommended.
2. Wait a week or so.
3. Post the proposal on the GDB Announcement mailing list.
4. Wait a week or so.
5. Go through and edit all relevant files and lines so that they are prefixed with the word
OBSOLETE.
6. Wait until the next GDB version, containing this obsolete code, has been released.
7. Remove the obsolete code.
Maintainer note: While removing old code is regrettable it is hopefully better for gdb’s long
term development. Firstly it helps the developers by removing code that is either no longer
relevant or simply wrong. Secondly since it removes any history associated with the file
(effectively clearing the slate) the developer has a much freer hand when it comes to fixing
broken files.
17.3 Before the Branch
The most important objective at this stage is to find and fix simple changes that become a
pain to track once the branch is created. For instance, configuration problems that stop gdb
from even building. If you can’t get the problem fixed, document it in the ‘gdb/PROBLEMS’
file.
Prompt for ‘gdb/NEWS’
People always forget. Send a post reminding them but also if you know something interesting
happened add it yourself. The schedule script will mention this in its e-mail.
Review ‘gdb/README’
Grab one of the nightly snapshots and then walk through the ‘gdb/README’ looking for
anything that can be improved. The schedule script will mention this in its e-mail.
Refresh any imported files.
A number of files are taken from external repositories. They include:
• ‘texinfo/texinfo.tex’
• ‘config.guess’ et. al. (see the top-level ‘MAINTAINERS’ file)
• ‘etc/standards.texi’, ‘etc/make-stds.texi’
Chapter 17: Releasing gdb
82
Check the ARI
A.R.I. is an awk script (Awk Regression Index ;-) that checks for a number of errors and
coding conventions. The checks include things like using malloc instead of xmalloc and
file naming problems. There shouldn’t be any regressions.
17.3.1 Review the bug data base
Close anything obviously fixed.
17.3.2 Check all cross targets build
The targets are listed in ‘gdb/MAINTAINERS’.
17.4 Cut the Branch
Create the branch
$ u=5.1
$ v=5.2
$ V=‘echo $v | sed ’s/\./_/g’‘
$ D=‘date -u +%Y-%m-%d‘
$ echo $u $V $D
5.1 5_2 2002-03-03
$ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
-D $D-gmt gdb_$V-$D-branchpoint insight+dejagnu
cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
-D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight+dejagnu
$ ^echo ^^
...
$ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
-b -r gdb_$V-$D-branchpoint gdb_$V-branch insight+dejagnu
cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
-b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight+dejagnu
$ ^echo ^^
...
$
•
•
•
•
•
by using -D YYYY-MM-DD-gmt the branch is forced to an exact date/time.
the trunk is first taged so that the branch point can easily be found
Insight (which includes GDB) and dejagnu are all tagged at the same time
‘version.in’ gets bumped to avoid version number conflicts
the reading of ‘.cvsrc’ is disabled using ‘-f’
Update ‘version.in’
$ u=5.1
$ v=5.2
$ V=‘echo $v | sed ’s/\./_/g’‘
$ echo $u $v$V
5.1 5_2
$ cd /tmp
$ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
-r gdb_$V-branch src/gdb/version.in
cvs -f -d :ext:sources.redhat.com:/cvs/src co
-r gdb_5_2-branch src/gdb/version.in
$ ^echo ^^
Chapter 17: Releasing gdb
83
U src/gdb/version.in
$ cd src/gdb
$ echo $u.90-0000-00-00-cvs > version.in
$ cat version.in
5.1.90-0000-00-00-cvs
$ cvs -f commit version.in
• ‘0000-00-00’ is used as a date to pump prime the version.in update mechanism
• ‘.90’ and the previous branch version are used as fairly arbitrary initial branch version
number
Update the web and news pages
Something?
Tweak cron to track the new branch
The file ‘gdbadmin/cron/crontab’ contains gdbadmin’s cron table. This file needs to be
updated so that:
• a daily timestamp is added to the file ‘version.in’
• the new branch is included in the snapshot process
See the file ‘gdbadmin/cron/README’ for how to install the updated cron table.
The file ‘gdbadmin/ss/README’ should also be reviewed to reflect any changes. That file
is copied to both the branch/ and current/ snapshot directories.
Update the NEWS and README files
The ‘NEWS’ file needs to be updated so that on the branch it refers to changes in the current
release while on the trunk it also refers to changes since the current release.
The ‘README’ file needs to be updated so that it refers to the current release.
Post the branch info
Send an announcement to the mailing lists:
• GDB Announcement mailing list
• GDB Discsussion mailing list and GDB Discsussion mailing list
Pragmatics: The branch creation is sent to the announce list to ensure that people people
not subscribed to the higher volume discussion list are alerted.
The announcement should include:
• the branch tag
• how to check out the branch using CVS
• the date/number of weeks until the release
• the branch commit policy still holds.
17.5 Stabilize the branch
Something goes here.
Chapter 17: Releasing gdb
84
17.6 Create a Release
The process of creating and then making available a release is broken down into a number
of stages. The first part addresses the technical process of creating a releasable tar ball.
The later stages address the process of releasing that tar ball.
When making a release candidate just the first section is needed.
17.6.1 Create a release candidate
The objective at this stage is to create a set of tar balls that can be made available as a
formal release (or as a less formal release candidate).
Freeze the branch
Send out an e-mail notifying everyone that the branch is frozen to [email protected].
Establish a few defaults.
$ b=gdb_5_2-branch
$ v=5.2
$ t=/sourceware/snapshot-tmp/gdbadmin-tmp
$ echo $t/$b/$v
/sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
$ mkdir -p $t/$b/$v
$ cd $t/$b/$v
$ pwd
/sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
$ which autoconf
/home/gdbadmin/bin/autoconf
$
Notes:
• Check the autoconf version carefully.
You want to be using the version taken from the ‘binutils’ snapshot directory, which can be found at
ftp://sources.redhat.com/pub/binutils/. It is very unlikely that a system
installed version of autoconf (e.g., ‘/usr/bin/autoconf’) is correct.
Check out the relevant modules:
$ for m in gdb insight dejagnu
do
( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
done
$
Note:
• The reading of ‘.cvsrc’ is disabled (‘-f’) so that there isn’t any confusion between
what is written here and what your local cvs really does.
Update relevant files.
‘gdb/NEWS’
Major releases get their comments added as part of the mainline. Minor releases
should probably mention any significant bugs that were fixed.
Don’t forget to include the ‘ChangeLog’ entry.
$
emacs gdb/src/gdb/NEWS
Chapter 17: Releasing gdb
85
...
c-x 4 a
...
c-x c-s c-x c-c
$ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
$ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
‘gdb/README’
You’ll need to update:
• the version
• the update date
• who did it
$ emacs gdb/src/gdb/README
...
c-x 4 a
...
c-x c-s c-x c-c
$ cp gdb/src/gdb/README insight/src/gdb/README
$ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
Maintainer note: Hopefully the ‘README’ file was reviewed before the initial
branch was cut so just a simple substitute is needed to get it updated.
Maintainer note: Other projects generate ‘README’ and ‘INSTALL’ from the core
documentation. This might be worth pursuing.
‘gdb/version.in’
$ echo $v > gdb/src/gdb/version.in
$ cat gdb/src/gdb/version.in
5.2
$ emacs gdb/src/gdb/version.in
...
c-x 4 a
... Bump to version ...
c-x c-s c-x c-c
$ cp gdb/src/gdb/version.in insight/src/gdb/version.in
$ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
‘dejagnu/src/dejagnu/configure.in’
Dejagnu is more complicated. The version number is a parameter to AM_INIT_
AUTOMAKE. Tweak it to read something like gdb-5.1.91.
Don’t forget to re-generate ‘configure’.
Don’t forget to include a ‘ChangeLog’ entry.
$ emacs dejagnu/src/dejagnu/configure.in
...
c-x 4 a
...
c-x c-s c-x c-c
$ ( cd dejagnu/src/dejagnu && autoconf )
Do the dirty work
This is identical to the process used to create the daily snapshot.
$ for m in gdb insight
do
Chapter 17: Releasing gdb
86
( cd $m/src && gmake -f src-release $m.tar )
done
$ ( m=dejagnu; cd $m/src && gmake -f src-release $m.tar.bz2 )
If the top level source directory does not have ‘src-release’ (gdb version 5.3.1 or
earlier), try these commands instead:
$ for m in gdb insight
do
( cd $m/src && gmake -f Makefile.in $m.tar )
done
$ ( m=dejagnu; cd $m/src && gmake -f Makefile.in $m.tar.bz2 )
Check the source files
You’re looking for files that have mysteriously disappeared. distclean has the habit of
deleting files it shouldn’t. Watch out for the ‘version.in’ update cronjob.
$ ( cd gdb/src && cvs -f -q -n update )
M djunpack.bat
? gdb-5.1.91.tar
? proto-toplev
... lots of generated files ...
M gdb/ChangeLog
M gdb/NEWS
M gdb/README
M gdb/version.in
... lots of generated files ...
$
Don’t worry about the ‘gdb.info-??’ or ‘gdb/p-exp.tab.c’. They were generated (and yes
‘gdb.info-1’ was also generated only something strange with CVS means that they didn’t
get supressed). Fixing it would be nice though.
Create compressed versions of the release
$ cp */src/*.tar .
$ cp */src/*.bz2 .
$ ls -F
dejagnu/ dejagnu-gdb-5.2.tar.bz2 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
$ for m in gdb insight
do
bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
done
$
Note:
• A pipe such as bunzip2 < xxx.bz2 | gzip -9 > xxx.gz is not since, in that mode, gzip
does not know the name of the file and, hence, can not include it in the compressed
file. This is also why the release process runs tar and bzip2 as separate passes.
17.6.2 Sanity check the tar ball
Pick a popular machine (Solaris/PPC?) and try the build on that.
$ bunzip2 < gdb-5.2.tar.bz2 | tar xpf $ cd gdb-5.2
$ ./configure
$ make
...
Chapter 17: Releasing gdb
87
$ ./gdb/gdb ./gdb/gdb
GNU gdb 5.2
...
(gdb) b main
Breakpoint 1 at 0x80732bc: file main.c, line 734.
(gdb) run
Starting program: /tmp/gdb-5.2/gdb/gdb
Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
734
catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
(gdb) print args
$1 = {argc = 136426532, argv = 0x821b7f0}
(gdb)
17.6.3 Make a release candidate available
If this is a release candidate then the only remaining steps are:
1. Commit ‘version.in’ and ‘ChangeLog’
2. Tweak ‘version.in’ (and ‘ChangeLog’ to read L.M.N-0000-00-00-cvs so that the version update process can restart.
3. Make the release candidate available in ftp://sources.redhat.com/pub/gdb/snapshots/branch
4. Notify the relevant mailing lists ( [email protected] and [email protected]
that the candidate is available.
17.6.4 Make a formal release available
(And you thought all that was required was to post an e-mail.)
Install on sware
Copy the new files to both the release and the old release directory:
$
$
cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
cp *.bz2 *.gz ~ftp/pub/gdb/releases
Clean up the releases directory so that only the most recent releases are available (e.g. keep
5.2 and 5.2.1 but remove 5.1):
$
$
cd ~ftp/pub/gdb/releases
rm ...
Update the file ‘README’ and ‘.message’ in the releases directory:
$ vi README
...
$ rm -f .message
$ ln README .message
Update the web pages.
‘htdocs/download/ANNOUNCEMENT’
This file, which is posted as the official announcement, includes:
• General announcement
• News. If making an M.N.1 release, retain the news from earlier M.N release.
• Errata
Chapter 17: Releasing gdb
88
‘htdocs/index.html’
‘htdocs/news/index.html’
‘htdocs/download/index.html’
These files include:
• announcement of the most recent release
• news entry (remember to update both the top level and the news directory).
These pages also need to be regenerate using index.sh.
‘download/onlinedocs/’
You need to find the magic command that is used to generate the online docs
from the ‘.tar.bz2’. The best way is to look in the output from one of the
nightly cron jobs and then just edit accordingly. Something like:
$ ~/ss/update-web-docs \
~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
$PWD/www \
/www/sourceware/htdocs/gdb/download/onlinedocs \
gdb
‘download/ari/’
Just like the online documentation. Something like:
$ /bin/sh ~/ss/update-web-ari \
~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
$PWD/www \
/www/sourceware/htdocs/gdb/download/ari \
gdb
Shadow the pages onto gnu
Something goes here.
Install the gdb tar ball on GNU
At the time of writing, the GNU machine was gnudist.gnu.org in ‘~ftp/gnu/gdb’.
Make the ‘ANNOUNCEMENT’
Post the ‘ANNOUNCEMENT’ file you created above to:
• GDB Announcement mailing list
• General GNU Announcement list (but delay it a day or so to let things get out)
• GDB Bug Report mailing list
17.6.5 Cleanup
The release is out but you’re still not finished.
Commit outstanding changes
In particular you’ll need to commit any changes to:
• ‘gdb/ChangeLog’
• ‘gdb/version.in’
• ‘gdb/NEWS’
• ‘gdb/README’
Chapter 18: Testsuite
89
Tag the release
Something like:
$ d=‘date -u +%Y-%m-%d‘
$ echo $d
2002-01-24
$ ( cd insight/src/gdb && cvs -f -q update )
$ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
Insight is used since that contains more of the release than gdb (dejagnu doesn’t get
tagged but I think we can live with that).
Mention the release on the trunk
Just put something in the ‘ChangeLog’ so that the trunk also indicates when the release
was made.
Restart ‘gdb/version.in’
If ‘gdb/version.in’ does not contain an ISO date such as 2002-01-24 then the daily
cronjob won’t update it. Having committed all the release changes it can be set to
‘5.2.0_0000-00-00-cvs’ which will restart things (yes the _ is important - it affects the
snapshot process).
Don’t forget the ‘ChangeLog’.
Merge into trunk
The files committed to the branch may also need changes merged into the trunk.
Revise the release schedule
Post a revised release schedule to GDB Discussion List with an updated announcement.
The schedule can be generated by running:
$
~/ss/schedule ‘date +%s‘ schedule
The first parameter is approximate date/time in seconds (from the epoch) of the most recent
release.
Also update the schedule cronjob.
17.7 Post release
Remove any OBSOLETE code.
18 Testsuite
The testsuite is an important component of the gdb package. While it is always worthwhile
to encourage user testing, in practice this is rarely sufficient; users typically use only a small
subset of the available commands, and it has proven all too common for a change to cause
a significant regression that went unnoticed for some time.
The gdb testsuite uses the DejaGNU testing framework. DejaGNU is built using Tcl
and expect. The tests themselves are calls to various Tcl procs; the framework runs all
the procs and summarizes the passes and fails.
Chapter 18: Testsuite
90
18.1 Using the Testsuite
To run the testsuite, simply go to the gdb object directory (or to the testsuite’s objdir) and
type make check. This just sets up some environment variables and invokes DejaGNU’s
runtest script. While the testsuite is running, you’ll get mentions of which test file is in
use, and a mention of any unexpected passes or fails. When the testsuite is finished, you’ll
get a summary that looks like this:
=== gdb Summary ===
#
#
#
#
#
#
of
of
of
of
of
of
expected passes
unexpected failures
unexpected successes
expected failures
unresolved testcases
untested testcases
6016
58
5
183
3
5
To run a specific test script, type:
make check RUNTESTFLAGS=’tests ’
where tests is a list of test script file names, separated by spaces.
The ideal test run consists of expected passes only; however, reality conspires to keep
us from this ideal. Unexpected failures indicate real problems, whether in gdb or in the
testsuite. Expected failures are still failures, but ones which have been decided are too hard
to deal with at the time; for instance, a test case might work everywhere except on AIX,
and there is no prospect of the AIX case being fixed in the near future. Expected failures
should not be added lightly, since you may be masking serious bugs in gdb. Unexpected
successes are expected fails that are passing for some reason, while unresolved and untested
cases often indicate some minor catastrophe, such as the compiler being unable to deal with
a test program.
When making any significant change to gdb, you should run the testsuite before and
after the change, to confirm that there are no regressions. Note that truly complete testing
would require that you run the testsuite with all supported configurations and a variety of
compilers; however this is more than really necessary. In many cases testing with a single
configuration is sufficient. Other useful options are to test one big-endian (Sparc) and one
little-endian (x86) host, a cross config with a builtin simulator (powerpc-eabi, mips-elf), or
a 64-bit host (Alpha).
If you add new functionality to gdb, please consider adding tests for it as well; this way
future gdb hackers can detect and fix their changes that break the functionality you added.
Similarly, if you fix a bug that was not previously reported as a test failure, please add a
test case for it. Some cases are extremely difficult to test, such as code that handles host
OS failures or bugs in particular versions of compilers, and it’s OK not to try to write tests
for all of those.
DejaGNU supports separate build, host, and target machines. However, some gdb test
scripts do not work if the build machine and the host machine are not the same. In such
an environment, these scripts will give a result of “UNRESOLVED”, like this:
UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host.
Chapter 18: Testsuite
91
18.2 Testsuite Organization
The testsuite is entirely contained in ‘gdb/testsuite’. While the testsuite includes some
makefiles and configury, these are very minimal, and used for little besides cleaning up,
since the tests themselves handle the compilation of the programs that gdb will run. The
file ‘testsuite/lib/gdb.exp’ contains common utility procs useful for all gdb tests, while
the directory ‘testsuite/config’ contains configuration-specific files, typically used for
special-purpose definitions of procs like gdb_load and gdb_start.
The tests themselves are to be found in ‘testsuite/gdb.*’ and subdirectories of those.
The names of the test files must always end with ‘.exp’. DejaGNU collects the test files
by wildcarding in the test directories, so both subdirectories and individual files get chosen
and run in alphabetical order.
The following table lists the main types of subdirectories and what they are for. Since
DejaGNU finds test files no matter where they are located, and since each test file sets up
its own compilation and execution environment, this organization is simply for convenience
and intelligibility.
‘gdb.base’
This is the base testsuite. The tests in it should apply to all configurations of
gdb (but generic native-only tests may live here). The test programs should be
in the subset of C that is valid K&R, ANSI/ISO, and C++ (#ifdefs are allowed
if necessary, for instance for prototypes).
‘gdb.lang ’
Language-specific tests for any language lang besides C. Examples are ‘gdb.cp’
and ‘gdb.java’.
‘gdb.platform ’
Non-portable tests. The tests are specific to a specific configuration (host or
target), such as HP-UX or eCos. Example is ‘gdb.hp’, for HP-UX.
‘gdb.compiler ’
Tests specific to a particular compiler. As of this writing (June 1999), there
aren’t currently any groups of tests in this category that couldn’t just as sensibly
be made platform-specific, but one could imagine a ‘gdb.gcc’, for tests of gdb’s
handling of GCC extensions.
‘gdb.subsystem ’
Tests that exercise a specific gdb subsystem in more depth. For instance,
‘gdb.disasm’ exercises various disassemblers, while ‘gdb.stabs’ tests pathways
through the stabs symbol reader.
18.3 Writing Tests
In many areas, the gdb tests are already quite comprehensive; you should be able to copy
existing tests to handle new cases.
You should try to use gdb_test whenever possible, since it includes cases to handle all
the unexpected errors that might happen. However, it doesn’t cost anything to add new test
procedures; for instance, ‘gdb.base/exprs.exp’ defines a test_expr that calls gdb_test
multiple times.
Chapter 19: Hints
92
Only use send_gdb and gdb_expect when absolutely necessary, such as when gdb has
several valid responses to a command.
The source language programs do not need to be in a consistent style. Since gdb is used
to debug programs written in many different styles, it’s worth having a mix of styles in
the testsuite; for instance, some gdb bugs involving the display of source lines would never
manifest themselves if the programs used GNU coding style uniformly.
19 Hints
Check the ‘README’ file, it often has useful information that does not appear anywhere else
in the directory.
19.1 Getting Started
gdb is a large and complicated program, and if you first starting to work on it, it can be
hard to know where to start. Fortunately, if you know how to go about it, there are ways
to figure out what is going on.
This manual, the gdb Internals manual, has information which applies generally to many
parts of gdb.
Information about particular functions or data structures are located in comments with
those functions or data structures. If you run across a function or a global variable which
does not have a comment correctly explaining what is does, this can be thought of as a bug
in gdb; feel free to submit a bug report, with a suggested comment if you can figure out
what the comment should say. If you find a comment which is actually wrong, be especially
sure to report that.
Comments explaining the function of macros defined in host, target, or native dependent
files can be in several places. Sometimes they are repeated every place the macro is defined.
Sometimes they are where the macro is used. Sometimes there is a header file which supplies
a default definition of the macro, and the comment is there. This manual also documents
all the available macros.
Start with the header files. Once you have some idea of how gdb’s internal symbol tables
are stored (see ‘symtab.h’, ‘gdbtypes.h’), you will find it much easier to understand the
code which uses and creates those symbol tables.
You may wish to process the information you are getting somehow, to enhance your
understanding of it. Summarize it, translate it to another language, add some (perhaps
trivial or non-useful) feature to gdb, use the code to predict what a test case would do and
write the test case and verify your prediction, etc. If you are reading code and your eyes
are starting to glaze over, this is a sign you need to use a more active approach.
Once you have a part of gdb to start with, you can find more specifically the part you
are looking for by stepping through each function with the next command. Do not use step
or you will quickly get distracted; when the function you are stepping through calls another
function try only to get a big-picture understanding (perhaps using the comment at the
beginning of the function being called) of what it does. This way you can identify which of
the functions being called by the function you are stepping through is the one which you
are interested in. You may need to examine the data structures generated at each stage,
Chapter 19: Hints
93
with reference to the comments in the header files explaining what the data structures are
supposed to look like.
Of course, this same technique can be used if you are just reading the code, rather than
actually stepping through it. The same general principle applies—when the code you are
looking at calls something else, just try to understand generally what the code being called
does, rather than worrying about all its details.
A good place to start when tracking down some particular area is with a command which
invokes that feature. Suppose you want to know how single-stepping works. As a gdb user,
you know that the step command invokes single-stepping. The command is invoked via
command tables (see ‘command.h’); by convention the function which actually performs
the command is formed by taking the name of the command and adding ‘_command’, or
in the case of an info subcommand, ‘_info’. For example, the step command invokes
the step_command function and the info display command invokes display_info. When
this convention is not followed, you might have to use grep or M-x tags-search in emacs,
or run gdb on itself and set a breakpoint in execute_command.
If all of the above fail, it may be appropriate to ask for information on bug-gdb. But
never post a generic question like “I was wondering if anyone could give me some tips
about understanding gdb”—if we had some magic secret we would put it in this manual.
Suggestions for improving the manual are always welcome, of course.
19.2 Debugging gdb with itself
If gdb is limping on your machine, this is the preferred way to get it fully functional. Be
warned that in some ancient Unix systems, like Ultrix 4.2, a program can’t be running
in one process while it is being debugged in another. Rather than typing the command
./gdb ./gdb, which works on Suns and such, you can copy ‘gdb’ to ‘gdb2’ and then type
./gdb ./gdb2.
When you run gdb in the gdb source directory, it will read a ‘.gdbinit’ file that sets
up some simple things to make debugging gdb easier. The info command, when executed
without a subcommand in a gdb being debugged by gdb, will pop you back up to the top
level gdb. See ‘.gdbinit’ for details.
If you use emacs, you will probably want to do a make TAGS after you configure your
distribution; this will put the machine dependent routines for your local machine where
they will be accessed first by M-.
Also, make sure that you’ve either compiled gdb with your local cc, or have run
fixincludes if you are compiling with gcc.
19.3 Submitting Patches
Thanks for thinking of offering your changes back to the community of gdb users. In general
we like to get well designed enhancements. Thanks also for checking in advance about the
best way to transfer the changes.
The gdb maintainers will only install “cleanly designed” patches. This manual summarizes what we believe to be clean design for gdb.
Chapter 19: Hints
94
If the maintainers don’t have time to put the patch in when it arrives, or if there is any
question about a patch, it goes into a large queue with everyone else’s patches and bug
reports.
The legal issue is that to incorporate substantial changes requires a copyright assignment from you and/or your employer, granting ownership of the changes to the Free Software Foundation. You can get the standard documents for doing this by sending mail to
[email protected] and asking for it. We recommend that people write in "All programs owned
by the Free Software Foundation" as "NAME OF PROGRAM", so that changes in many
programs (not just gdb, but GAS, Emacs, GCC, etc) can be contributed with only one
piece of legalese pushed through the bureaucracy and filed with the FSF. We can’t start
merging changes until this paperwork is received by the FSF (their rules, which we follow
since we maintain it for them).
Technically, the easiest way to receive changes is to receive each feature as a small
context diff or unidiff, suitable for patch. Each message sent to me should include the
changes to C code and header files for a single feature, plus ‘ChangeLog’ entries for each
directory where files were modified, and diffs for any changes needed to the manuals
(‘gdb/doc/gdb.texinfo’ or ‘gdb/doc/gdbint.texinfo’). If there are a lot of changes for
a single feature, they can be split down into multiple messages.
In this way, if we read and like the feature, we can add it to the sources with a single
patch command, do some testing, and check it in. If you leave out the ‘ChangeLog’, we
have to write one. If you leave out the doc, we have to puzzle out what needs documenting.
Etc., etc.
The reason to send each change in a separate message is that we will not install some
of the changes. They’ll be returned to you with questions or comments. If we’re doing our
job correctly, the message back to you will say what you have to fix in order to make the
change acceptable. The reason to have separate messages for separate features is so that
the acceptable changes can be installed while one or more changes are being reworked. If
multiple features are sent in a single message, we tend to not put in the effort to sort out
the acceptable changes from the unacceptable, so none of the features get installed until all
are acceptable.
If this sounds painful or authoritarian, well, it is. But we get a lot of bug reports and
a lot of patches, and many of them don’t get installed because we don’t have the time to
finish the job that the bug reporter or the contributor could have done. Patches that arrive
complete, working, and well designed, tend to get installed on the day they arrive. The
others go into a queue and get installed as time permits, which, since the maintainers have
many demands to meet, may not be for quite some time.
Please send patches directly to the gdb maintainers.
19.4 Obsolete Conditionals
Fragments of old code in gdb sometimes reference or set the following configuration macros.
They should not be used by new code, and old uses should be removed as those parts of
the debugger are otherwise touched.
STACK_END_ADDR
This macro used to define where the end of the stack appeared, for use in
interpreting core file formats that don’t record this address in the core file itself.
Appendix A: gdb Currently available observers
95
This information is now configured in BFD, and gdb gets the info portably
from there. The values in gdb’s configuration files should be moved into BFD
configuration files (if needed there), and deleted from all of gdb’s config files.
Any ‘foo-xdep.c’ file that references STACK END ADDR is so old that it has
never been converted to use BFD. Now that’s old!
Appendix A gdb Currently available observers
A.1 Implementation rationale
An observer is an entity which is interested in being notified when GDB reaches certain
states, or certain events occur in GDB. The entity being observed is called the subject. To
receive notifications, the observer attaches a callback to the subject. One subject can have
several observers.
‘observer.c’ implements an internal generic low-level event notification mechanism.
This generic event notification mechanism is then re-used to implement the exported highlevel notification management routines for all possible notifications.
The current implementation of the generic observer provides support for contextual data.
This contextual data is given to the subject when attaching the callback. In return, the
subject will provide this contextual data back to the observer as a parameter of the callback.
Note that the current support for the contextual data is only partial, as it lacks a
mechanism that would deallocate this data when the callback is detached. This is not a
problem so far, as this contextual data is only used internally to hold a function pointer.
Later on, if a certain observer needs to provide support for user-level contextual data, then
the generic notification mechanism will need to be enhanced to allow the observer to provide
a routine to deallocate the data when attaching the callback.
The observer implementation is also currently not reentrant. In particular, it is therefore
not possible to call the attach or detach routines during a notification.
A.2 Debugging
Observer notifications can be traced using the command ‘set debug observer 1’ (see section “Optional messages about internal happenings” in Debugging with GDBN ).
A.3 normal_stop Notifications
gdb notifies all normal_stop observers when the inferior execution has just stopped, the
associated messages and annotations have been printed, and the control is about to be
returned to the user.
Note that the normal_stop notification is not emitted when the execution stops due to
a breakpoint, and this breakpoint has a condition that is not met. If the breakpoint has
any associated commands list, the commands are executed after the notification is emitted.
The following interfaces are available to manage observers:
Appendix B: GNU Free Documentation License
extern struct observer *observer attach event (observer event ftype
*f )
96
[Function]
Using the function f, create an observer that is notified when ever event occures,
return the observer.
extern void observer detach event (struct observer *observer );
[Function]
Remove observer from the list of observers to be notified when event occurs.
extern void observer notify event (void);
[Function]
Send a notification to all event observers.
The following observable events are defined:
void normal_stop (struct bpstats *bs )
[Function]
The inferior has stopped for real.
void target_changed (struct target ops *target )
[Function]
The target’s register contents have changed.
void executable_changed (void *unused_args )
[Function]
The executable being debugged by GDB has changed: The user decided to debug a
different program, or the program he was debugging has been modified since being
loaded by the debugger (by being recompiled, for instance).
void inferior_created (struct target ops *objfile, int from_tty )
[Function]
gdb has just connected to an inferior. For ‘run’, gdb calls this observer while the inferior is still stopped at the entry-point instruction. For ‘attach’ and ‘core’, gdb calls
this observer immediately after connecting to the inferior, and before any information
on the inferior has been printed.
void solib_loaded (struct so list *solib )
[Function]
The shared library specified by solib has been loaded. Note that when gdb calls this
observer, the library’s symbols probably haven’t been loaded yet.
void solib_unloaded (struct so list *solib )
[Function]
The shared library specified by solib has been unloaded.
Appendix B GNU Free Documentation License
Version 1.2, November 2002
c 2000,2001,2002 Free Software Foundation, Inc.
Copyright 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other functional and
useful document free in the sense of freedom: to assure everyone the effective freedom
Appendix B: GNU Free Documentation License
97
to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible for modifications
made by others.
This License is a kind of “copyleft”, which means that derivative works of the document
must themselves be free in the same sense. It complements the GNU General Public
License, which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for free software, because
free software needs free documentation: a free program should come with manuals
providing the same freedoms that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License principally for
works whose purpose is instruction or reference.
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that contains a
notice placed by the copyright holder saying it can be distributed under the terms
of this License. Such a notice grants a world-wide, royalty-free license, unlimited in
duration, to use that work under the conditions stated herein. The “Document”,
below, refers to any such manual or work. Any member of the public is a licensee, and
is addressed as “you”. You accept the license if you copy, modify or distribute the work
in a way requiring permission under copyright law.
A “Modified Version” of the Document means any work containing the Document or
a portion of it, either copied verbatim, or with modifications and/or translated into
another language.
A “Secondary Section” is a named appendix or a front-matter section of the Document
that deals exclusively with the relationship of the publishers or authors of the Document
to the Document’s overall subject (or to related matters) and contains nothing that
could fall directly within that overall subject. (Thus, if the Document is in part a
textbook of mathematics, a Secondary Section may not explain any mathematics.) The
relationship could be a matter of historical connection with the subject or with related
matters, or of legal, commercial, philosophical, ethical or political position regarding
them.
The “Invariant Sections” are certain Secondary Sections whose titles are designated, as
being those of Invariant Sections, in the notice that says that the Document is released
under this License. If a section does not fit the above definition of Secondary then it is
not allowed to be designated as Invariant. The Document may contain zero Invariant
Sections. If the Document does not identify any Invariant Sections then there are none.
The “Cover Texts” are certain short passages of text that are listed, as Front-Cover
Texts or Back-Cover Texts, in the notice that says that the Document is released under
this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
A “Transparent” copy of the Document means a machine-readable copy, represented
in a format whose specification is available to the general public, that is suitable for
revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing
Appendix B: GNU Free Documentation License
98
editor, and that is suitable for input to text formatters or for automatic translation to
a variety of formats suitable for input to text formatters. A copy made in an otherwise
Transparent file format whose markup, or absence of markup, has been arranged to
thwart or discourage subsequent modification by readers is not Transparent. An image
format is not Transparent if used for any substantial amount of text. A copy that is
not “Transparent” is called “Opaque”.
Examples of suitable formats for Transparent copies include plain ascii without
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The “Title Page” means, for a printed book, the title page itself, plus such following
pages as are needed to hold, legibly, the material this License requires to appear in the
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A section “Entitled XYZ” means a named subunit of the Document whose title either
is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in
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as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve
the Title” of such a section when you modify the Document means that it remains a
section “Entitled XYZ” according to this definition.
The Document may include Warranty Disclaimers next to the notice which states that
this License applies to the Document. These Warranty Disclaimers are considered to
be included by reference in this License, but only as regards disclaiming warranties:
any other implication that these Warranty Disclaimers may have is void and has no
effect on the meaning of this License.
2. VERBATIM COPYING
You may copy and distribute the Document in any medium, either commercially or
noncommercially, provided that this License, the copyright notices, and the license
notice saying this License applies to the Document are reproduced in all copies, and
that you add no other conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further copying of the copies
you make or distribute. However, you may accept compensation in exchange for copies.
If you distribute a large enough number of copies you must also follow the conditions
in section 3.
You may also lend copies, under the same conditions stated above, and you may publicly
display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have printed covers) of
the Document, numbering more than 100, and the Document’s license notice requires
Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all
Appendix B: GNU Free Documentation License
99
these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover. Both covers must also clearly and legibly identify you as the publisher
of these copies. The front cover must present the full title with all words of the title
equally prominent and visible. You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve the title of the
Document and satisfy these conditions, can be treated as verbatim copying in other
respects.
If the required texts for either cover are too voluminous to fit legibly, you should put
the first ones listed (as many as fit reasonably) on the actual cover, and continue the
rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more than 100,
you must either include a machine-readable Transparent copy along with each Opaque
copy, or state in or with each Opaque copy a computer-network location from which
the general network-using public has access to download using public-standard network
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you use the latter option, you must take reasonably prudent steps, when you begin
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remain thus accessible at the stated location until at least one year after the last time
you distribute an Opaque copy (directly or through your agents or retailers) of that
edition to the public.
It is requested, but not required, that you contact the authors of the Document well
before redistributing any large number of copies, to give them a chance to provide you
with an updated version of the Document.
4. MODIFICATIONS
You may copy and distribute a Modified Version of the Document under the conditions
of sections 2 and 3 above, provided that you release the Modified Version under precisely
this License, with the Modified Version filling the role of the Document, thus licensing
distribution and modification of the Modified Version to whoever possesses a copy of
it. In addition, you must do these things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title distinct from that of the
Document, and from those of previous versions (which should, if there were any,
be listed in the History section of the Document). You may use the same title as
a previous version if the original publisher of that version gives permission.
B. List on the Title Page, as authors, one or more persons or entities responsible for
authorship of the modifications in the Modified Version, together with at least five
of the principal authors of the Document (all of its principal authors, if it has fewer
than five), unless they release you from this requirement.
C. State on the Title page the name of the publisher of the Modified Version, as the
publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications adjacent to the other
copyright notices.
F. Include, immediately after the copyright notices, a license notice giving the public
permission to use the Modified Version under the terms of this License, in the form
shown in the Addendum below.
Appendix B: GNU Free Documentation License
100
G. Preserve in that license notice the full lists of Invariant Sections and required Cover
Texts given in the Document’s license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled “History”, Preserve its Title, and add to it an item
stating at least the title, year, new authors, and publisher of the Modified Version
as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document
as given on its Title Page, then add an item describing the Modified Version as
stated in the previous sentence.
J. Preserve the network location, if any, given in the Document for public access to
a Transparent copy of the Document, and likewise the network locations given in
the Document for previous versions it was based on. These may be placed in the
“History” section. You may omit a network location for a work that was published
at least four years before the Document itself, or if the original publisher of the
version it refers to gives permission.
K. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title
of the section, and preserve in the section all the substance and tone of each of the
contributor acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document, unaltered in their text and
in their titles. Section numbers or the equivalent are not considered part of the
section titles.
M. Delete any section Entitled “Endorsements”. Such a section may not be included
in the Modified Version.
N. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in
title with any Invariant Section.
O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or appendices that qualify
as Secondary Sections and contain no material copied from the Document, you may at
your option designate some or all of these sections as invariant. To do this, add their
titles to the list of Invariant Sections in the Modified Version’s license notice. These
titles must be distinct from any other section titles.
You may add a section Entitled “Endorsements”, provided it contains nothing but
endorsements of your Modified Version by various parties—for example, statements of
peer review or that the text has been approved by an organization as the authoritative
definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up
to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified
Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or by arrangement
made by the same entity you are acting on behalf of, you may not add another; but
you may replace the old one, on explicit permission from the previous publisher that
added the old one.
Appendix B: GNU Free Documentation License
5.
6.
7.
8.
101
The author(s) and publisher(s) of the Document do not by this License give permission
to use their names for publicity for or to assert or imply endorsement of any Modified
Version.
COMBINING DOCUMENTS
You may combine the Document with other documents released under this License,
under the terms defined in section 4 above for modified versions, provided that you
include in the combination all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your combined work in its license
notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical
Invariant Sections may be replaced with a single copy. If there are multiple Invariant
Sections with the same name but different contents, make the title of each such section
unique by adding at the end of it, in parentheses, the name of the original author or
publisher of that section if known, or else a unique number. Make the same adjustment
to the section titles in the list of Invariant Sections in the license notice of the combined
work.
In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any
sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You
must delete all sections Entitled “Endorsements.”
COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents released
under this License, and replace the individual copies of this License in the various
documents with a single copy that is included in the collection, provided that you
follow the rules of this License for verbatim copying of each of the documents in all
other respects.
You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted
document, and follow this License in all other respects regarding verbatim copying of
that document.
AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate and independent
documents or works, in or on a volume of a storage or distribution medium, is called
an “aggregate” if the copyright resulting from the compilation is not used to limit the
legal rights of the compilation’s users beyond what the individual works permit. When
the Document is included in an aggregate, this License does not apply to the other
works in the aggregate which are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document,
then if the Document is less than one half of the entire aggregate, the Document’s Cover
Texts may be placed on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form. Otherwise they
must appear on printed covers that bracket the whole aggregate.
TRANSLATION
Translation is considered a kind of modification, so you may distribute translations
of the Document under the terms of section 4. Replacing Invariant Sections with
Appendix B: GNU Free Documentation License
102
translations requires special permission from their copyright holders, but you may
include translations of some or all Invariant Sections in addition to the original versions
of these Invariant Sections. You may include a translation of this License, and all the
license notices in the Document, and any Warranty Disclaimers, provided that you
also include the original English version of this License and the original versions of
those notices and disclaimers. In case of a disagreement between the translation and
the original version of this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require
changing the actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document except as expressly
provided for under this License. Any other attempt to copy, modify, sublicense or
distribute the Document is void, and will automatically terminate your rights under
this License. However, parties who have received copies, or rights, from you under this
License will not have their licenses terminated so long as such parties remain in full
compliance.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of the GNU Free
Documentation License from time to time. Such new versions will be similar in spirit
to the present version, but may differ in detail to address new problems or concerns.
See http://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the Document
specifies that a particular numbered version of this License “or any later version”
applies to it, you have the option of following the terms and conditions either of that
specified version or of any later version that has been published (not as a draft) by
the Free Software Foundation. If the Document does not specify a version number of
this License, you may choose any version ever published (not as a draft) by the Free
Software Foundation.
Appendix B: Index
103
B.1 ADDENDUM: How to use this License for your
documents
To use this License in a document you have written, include a copy of the License in the
document and put the following copyright and license notices just after the title page:
Copyright (C) year your name.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ‘‘GNU
Free Documentation License’’.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the
“with...Texts.” line with this:
with the Invariant Sections being list their titles, with
the Front-Cover Texts being list, and with the Back-Cover Texts
being list.
If you have Invariant Sections without Cover Texts, or some other combination of the
three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing
these examples in parallel under your choice of free software license, such as the GNU
General Public License, to permit their use in free software.
Index
*
*ADDRESS_CLASS_TYPE_FLAGS_TO_NAME. . . . . . . . . 38
*gdbarch_data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
_initialize_language . . . . . . . . . . . . . . . . . . . . . . . 30
A
a.out format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
abstract interpretation of function prologues . . . . 3
add_cmd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
add_com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
add_setshow_cmd . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
add_setshow_cmd_full . . . . . . . . . . . . . . . . . . . . . . . 12
add_symtab_fns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
adding a new host . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
adding a symbol-reading module . . . . . . . . . . . . . . 23
adding a target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
adding debugging info reader . . . . . . . . . . . . . . . . . 28
adding source language . . . . . . . . . . . . . . . . . . . . . . . 29
ADDR_BITS_REMOVE . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
address classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
address representation. . . . . . . . . . . . . . . . . . . . . . . . 36
address spaces, separate data and code . . . . . . . . 36
ADDRESS_CLASS_NAME_to_TYPE_FLAGS . . . . . . . . . . 38
ADDRESS_CLASS_NAME_TO_TYPE_FLAGS . . . . . . . . . . 42
ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P . . . . . . . 42
ADDRESS_CLASS_TYPE_FLAGS . . . . . . . . . . . . . . . . . . 38
ADDRESS_CLASS_TYPE_FLAGS (byte_size,
dwarf2_addr_class ) . . . . . . . . . . . . . . . . . . . . 42
ADDRESS_CLASS_TYPE_FLAGS_P . . . . . . . . . . . . . . . . 42
ADDRESS_CLASS_TYPE_FLAGS_TO_NAME . . . . . . . . . . 42
ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P . . . . . . . 42
ADDRESS_TO_POINTER . . . . . . . . . . . . . . . . . . . . . 38, 43
ADJUST_BREAKPOINT_ADDRESS . . . . . . . . . . . . . . . . . 44
algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ALIGN_STACK_ON_STARTUP . . . . . . . . . . . . . . . . . . . . 32
allocate_symtab . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
assumptions about targets . . . . . . . . . . . . . . . . . . . . 74
ATTR_NORETURN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
B
BELIEVE_PCC_PROMOTION . . . . . . . . . . . . . . . . . . . . . 43
BFD library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
BIG_BREAKPOINT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
BITS_BIG_ENDIAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
BPT_VECTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
BREAKPOINT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6, 43
breakpoint address adjusted . . . . . . . . . . . . . . . . . . 44
BREAKPOINT_FROM_PC . . . . . . . . . . . . . . . . . . . . . . . . . 43
breakpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
bug-gdb mailing list . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Appendix B: Index
104
C
C data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
call frame information . . . . . . . . . . . . . . . . . . . . . . . . . 3
call stack frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
CALL_DUMMY_LOCATION . . . . . . . . . . . . . . . . . . . . . . . . 44
CANNOT_FETCH_REGISTER . . . . . . . . . . . . . . . . . . . . . 44
CANNOT_STEP_HW_WATCHPOINTS . . . . . . . . . . . . . . . . . 8
CANNOT_STORE_REGISTER . . . . . . . . . . . . . . . . . . . . . 45
CC_HAS_LONG_LONG . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
CFI (call frame information) . . . . . . . . . . . . . . . . . . . 3
char . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
checkpoints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
CHILD_PREPARE_TO_STORE . . . . . . . . . . . . . . . . . . . . 63
cleanup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15, 16
cleanups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
CLEAR_SOLIB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
CLI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
code pointers, word-addressed . . . . . . . . . . . . . . . . 36
coding standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
COFF debugging info . . . . . . . . . . . . . . . . . . . . . . . . 28
COFF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
command implementation . . . . . . . . . . . . . . . . . . . . 93
command interpreter . . . . . . . . . . . . . . . . . . . . . . . . . 12
comment formatting . . . . . . . . . . . . . . . . . . . . . . . . . 72
compiler warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
CONVERT_REGISTER_P . . . . . . . . . . . . . . . . . . . . . 41, 45
converting between pointers and addresses . . . . . 36
converting integers to addresses . . . . . . . . . . . . . . . 50
converting targets to multi-arch . . . . . . . . . . . . . . . 58
CRLF_SOURCE_FILES . . . . . . . . . . . . . . . . . . . . . . . . . . 32
current_language . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
D
D10V addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
data output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
data-pointer, per-architecture/per-module . . . . .
DEBUG_PTRACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
debugging gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DECR_PC_AFTER_BREAK . . . . . . . . . . . . . . . . . . . . . . . .
DEFAULT_PROMPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
deprecate_cmd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DEPRECATED_BIG_REMOTE_BREAKPOINT . . . . . . . . . .
DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS . .
DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P
........................................
DEPRECATED_FP_REGNUM . . . . . . . . . . . . . . . . . . . . . . .
DEPRECATED_FRAME_CHAIN . . . . . . . . . . . . . . . . . . . .
DEPRECATED_FRAME_CHAIN_VALID . . . . . . . . . . . . . .
DEPRECATED_FRAME_INIT_SAVED_REGS . . . . . . . . . .
DEPRECATED_FRAME_SAVED_PC . . . . . . . . . . . . . . . . .
DEPRECATED_FRAMELESS_FUNCTION_INVOCATION
........................................
DEPRECATED_FUNCTION_START_OFFSET . . . . . . . . . .
DEPRECATED_GET_SAVED_REGISTER . . . . . . . . . . . . .
DEPRECATED_IBM6000_TARGET . . . . . . . . . . . . . . . . .
DEPRECATED_INIT_EXTRA_FRAME_INFO . . . . . . . . . .
DEPRECATED_INIT_FRAME_PC . . . . . . . . . . . . . . . . . .
36
16
68
65
93
45
32
12
43
46
46
46
46
47
47
47
46
48
48
48
49
49
DEPRECATED_LITTLE_REMOTE_BREAKPOINT . . . . . .
DEPRECATED_POP_FRAME . . . . . . . . . . . . . . . . . . . . . . .
DEPRECATED_PUSH_ARGUMENTS. . . . . . . . . . . . . . . . .
DEPRECATED_REG_STRUCT_HAS_ADDR . . . . . . . . 52,
DEPRECATED_REGISTER_RAW_SIZE. . . . . . . . . . . 40,
DEPRECATED_REGISTER_VIRTUAL_SIZE . . . . . . 40,
DEPRECATED_REMOTE_BREAKPOINT . . . . . . . . . . . . . .
DEPRECATED_SIGTRAMP_END . . . . . . . . . . . . . . . . . . .
DEPRECATED_SIGTRAMP_START . . . . . . . . . . . . . . . . .
DEPRECATED_STACK_ALIGN . . . . . . . . . . . . . . . . . . . .
DEPRECATED_USE_STRUCT_CONVENTION . . . . . . . . . .
deprecating commands . . . . . . . . . . . . . . . . . . . . . . .
design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DEV_TTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DIRNAME_SEPARATOR . . . . . . . . . . . . . . . . . . . . . . . . . .
DISABLE_UNSETTABLE_BREAK . . . . . . . . . . . . . . . . . .
discard_cleanups . . . . . . . . . . . . . . . . . . . . . . . . . . .
do_cleanups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DOS text files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DW AT address class . . . . . . . . . . . . . . . . . . . . . . . .
DW AT byte size . . . . . . . . . . . . . . . . . . . . . . . . . . .
DWARF 1 debugging info . . . . . . . . . . . . . . . . . . . .
DWARF 2 debugging info . . . . . . . . . . . . . . . . . . . .
DWARF_REG_TO_REGNUM . . . . . . . . . . . . . . . . . . . . . . . .
DWARF2_REG_TO_REGNUM . . . . . . . . . . . . . . . . . . . . . . .
43
52
52
53
50
51
43
49
49
54
56
12
74
32
75
45
67
67
32
38
38
28
28
45
45
E
ECOFF debugging info. . . . . . . . . . . . . . . . . . . . . . .
ECOFF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ECOFF_REG_TO_REGNUM . . . . . . . . . . . . . . . . . . . . . . . .
ELF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
END_OF_TEXT_DEFAULT . . . . . . . . . . . . . . . . . . . . . . . .
evaluate_subexp . . . . . . . . . . . . . . . . . . . . . . . . . . . .
executable_changed . . . . . . . . . . . . . . . . . . . . . . . . .
experimental branches . . . . . . . . . . . . . . . . . . . . . . .
expression evaluation routines . . . . . . . . . . . . . . . .
expression parser . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EXTRACT_RETURN_VALUE . . . . . . . . . . . . . . . . . . . . . . .
extract_typed_address . . . . . . . . . . . . . . . . . . . . .
28
27
45
27
45
29
96
79
29
29
46
37
F
FDL, GNU Free Documentation License . . . . . . . 96
fetch_core_registers . . . . . . . . . . . . . . . . . . . . . . . 62
FETCH_INFERIOR_REGISTERS . . . . . . . . . . . . . . . . . . 63
field output functions . . . . . . . . . . . . . . . . . . . . . . . . 16
file names, portability . . . . . . . . . . . . . . . . . . . . . . . . 75
FILENAME_CMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
find_pc_function . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
find_pc_line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
find_sym_fns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
finding a symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
fine-tuning gdbarch structure . . . . . . . . . . . . . . . . . 34
FOPEN_RB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
FP0_REGNUM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
frame, unwind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Appendix B: Index
frame_align . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
FRAME_NUM_ARGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
frame_pop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
frame_register_unwind. . . . . . . . . . . . . . . . . . . . . . . 3
full symbol table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
function prototypes . . . . . . . . . . . . . . . . . . . . . . . . . . 73
function usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
FUNCTION_EPILOGUE_SIZE . . . . . . . . . . . . . . . . . . . . 47
fundamental types . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
G
GCC_COMPILED_FLAG_SYMBOL . . . . . . . . . . . . . . . . . . 48
GCC2_COMPILED_FLAG_SYMBOL . . . . . . . . . . . . . . . . . 48
gdb_MULTI_ARCH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
gdb_osabi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_ARM_APCS . . . . . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_ARM_EABI_V1 . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_ARM_EABI_V2 . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_FREEBSD_AOUT . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_FREEBSD_ELF . . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_GO32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_HURD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_LINUX . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_NETBSD_AOUT . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_NETBSD_ELF . . . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_NETWARE . . . . . . . . . . . . . . . . . . . . . . . . . . 35
GDB_OSABI_OSF1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_SOLARIS . . . . . . . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_SVR4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_UNKNOWN . . . . . . . . . . . . . . . . . . . . . . . . . . 34
GDB_OSABI_WINCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
gdb_TARGET_IS_HPPA . . . . . . . . . . . . . . . . . . . . . . . . 48
gdbarch_data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
gdbarch_in_function_epilogue_p . . . . . . . . . . . . 49
gdbarch_init_osabi . . . . . . . . . . . . . . . . . . . . . . . . . 35
gdbarch_register_osabi . . . . . . . . . . . . . . . . . . . . 35
gdbarch_register_osabi_sniffer . . . . . . . . . . . . 35
gdbarch_return_value . . . . . . . . . . . . . . . . . . . . . . . 53
gdbINIT_FILENAME . . . . . . . . . . . . . . . . . . . . . . . . . . 32
generic host support . . . . . . . . . . . . . . . . . . . . . . . . . 31
get_frame_register . . . . . . . . . . . . . . . . . . . . . . . . . . 3
get_frame_type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
GET_LONGJMP_TARGET . . . . . . . . . . . . . . . . . . . 7, 48, 63
H
hardware breakpoints . . . . . . . . . . . . . . . . . . . . . . . . . 5
hardware watchpoints . . . . . . . . . . . . . . . . . . . . . . . . . 7
HAVE_CONTINUABLE_WATCHPOINT . . . . . . . . . . . . . . . . 8
HAVE_DOS_BASED_FILE_SYSTEM . . . . . . . . . . . . . . . . 75
HAVE_LONG_DOUBLE . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
HAVE_MMAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
HAVE_NONSTEPPABLE_WATCHPOINT . . . . . . . . . . . . . . . 8
HAVE_STEPPABLE_WATCHPOINT . . . . . . . . . . . . . . . . . . 8
HAVE_TERMIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
host . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
host, adding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
105
I
i386_cleanup_dregs . . . . . . . . . . . . . . . . . . . . . . . . . 11
I386_DR_LOW_GET_STATUS . . . . . . . . . . . . . . . . . . . . . 9
I386_DR_LOW_RESET_ADDR . . . . . . . . . . . . . . . . . . . . . 9
I386_DR_LOW_SET_ADDR . . . . . . . . . . . . . . . . . . . . . . . . 9
I386_DR_LOW_SET_CONTROL . . . . . . . . . . . . . . . . . . . . 9
i386_insert_hw_breakpoint . . . . . . . . . . . . . . . . . 10
i386_insert_watchpoint . . . . . . . . . . . . . . . . . . . . 10
i386_region_ok_for_watchpoint . . . . . . . . . . . . . 10
i386_remove_hw_breakpoint . . . . . . . . . . . . . . . . . 10
i386_remove_watchpoint . . . . . . . . . . . . . . . . . . . . 10
i386_stopped_by_hwbp . . . . . . . . . . . . . . . . . . . . . . . 11
i386_stopped_by_watchpoint . . . . . . . . . . . . . . . . 10
i386_stopped_data_address . . . . . . . . . . . . . . . . . 10
I386_USE_GENERIC_WATCHPOINTS . . . . . . . . . . . . . . . 9
IN_SOLIB_CALL_TRAMPOLINE . . . . . . . . . . . . . . . . . . 49
IN_SOLIB_DYNSYM_RESOLVE_CODE . . . . . . . . . . . . . . 49
IN_SOLIB_RETURN_TRAMPOLINE . . . . . . . . . . . . . . . . 49
inferior_created . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
INNER_THAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
insert or remove hardware breakpoint . . . . . . . . . . 6
insert or remove hardware watchpoint . . . . . . . . . . 8
insert or remove software breakpoint . . . . . . . . . . . 6
INT_MAX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
INT_MIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
INTEGER_TO_ADDRESS . . . . . . . . . . . . . . . . . . . . . . . . . 50
IS_ABSOLUTE_PATH . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
IS_DIR_SEPARATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
ISATTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
item output functions . . . . . . . . . . . . . . . . . . . . . . . . 16
K
KERNEL_U_ADDR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
KERNEL_U_ADDR_HPUX . . . . . . . . . . . . . . . . . . . . . . . . . 64
L
L_SET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
language parser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
language support . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
legal papers for code contributions . . . . . . . . . . . . 94
length_of_subexp . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
libgdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21, 22
libiberty library . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
line wrap in output . . . . . . . . . . . . . . . . . . . . . . . . . . 70
lint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
list output functions . . . . . . . . . . . . . . . . . . . . . . . . . 14
LITTLE_BREAKPOINT . . . . . . . . . . . . . . . . . . . . . . . . . . 43
long long data type . . . . . . . . . . . . . . . . . . . . . . . . . 33
LONG_MAX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
LONGEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
longjmp debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
lookup symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
LSEEK_NOT_LINEAR . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Appendix B: Index
106
M
make_cleanup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
making a new release of gdb . . . . . . . . . . . . . . . . . .
memory representation . . . . . . . . . . . . . . . . . . . . . . .
MEMORY_INSERT_BREAKPOINT . . . . . . . . . . . . . . . . . .
MEMORY_REMOVE_BREAKPOINT . . . . . . . . . . . . . . . . . .
minimal symbol table . . . . . . . . . . . . . . . . . . . . . . . .
minsymtabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
mmap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
multi-arch data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
67
80
40
44
44
25
25
32
68
N
NAME_OF_MALLOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NATDEPFILES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
native conditionals . . . . . . . . . . . . . . . . . . . . . . . . . . .
native core files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
native debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . .
nesting level in ui_out functions . . . . . . . . . . . . . .
Netware Loadable Module format . . . . . . . . . . . . .
new year procedure . . . . . . . . . . . . . . . . . . . . . . . . . .
NO_HIF_SUPPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NO_STD_REGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NORETURN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
normal_stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
normal_stop observer . . . . . . . . . . . . . . . . . . . . . . . .
notification about inferior execution stop . . . . . .
notifications about changes in internals . . . . . . . .
57
61
63
62
61
14
27
80
50
32
33
96
95
95
12
O
object file formats . . . . . . . . . . . . . . . . . . . . . . . . . . .
observer pattern interface . . . . . . . . . . . . . . . . . . . .
observers implementation rationale . . . . . . . . . . . .
obsolete code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
obstacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ONE_PROCESS_WRITETEXT . . . . . . . . . . . . . . . . . . . . .
op_print_tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
opcodes library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OS ABI variants . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OS9K_VARIABLES_INSIDE_BLOCK . . . . . . . . . . . . . . .
26
12
95
94
66
64
30
65
34
57
P
PARM_BOUNDARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
parse_exp_1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
partial symbol table. . . . . . . . . . . . . . . . . . . . . . . . . .
PC_LOAD_SEGMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PC_REGNUM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PE-COFF format . . . . . . . . . . . . . . . . . . . . . . . . . . . .
per-architecture module data . . . . . . . . . . . . . . . . .
pointer representation . . . . . . . . . . . . . . . . . . . . . . . .
POINTER_TO_ADDRESS . . . . . . . . . . . . . . . . . . . . . 37,
portability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
portable file name handling . . . . . . . . . . . . . . . . . . .
porting to new machines . . . . . . . . . . . . . . . . . . . . .
prefixify_subexp . . . . . . . . . . . . . . . . . . . . . . . . . . .
PRINT_FLOAT_INFO . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
30
25
52
52
27
68
36
50
75
75
76
29
45
print_registers_info . . . . . . . . . . . . . . . . . . . . . . . 45
print_subexp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
PRINT_VECTOR_INFO . . . . . . . . . . . . . . . . . . . . . . . . . . 45
PRINTF_HAS_LONG_DOUBLE . . . . . . . . . . . . . . . . . . . . 33
PRINTF_HAS_LONG_LONG . . . . . . . . . . . . . . . . . . . . . . . 33
PROC_NAME_FMT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
PROCESS_LINENUMBER_HOOK . . . . . . . . . . . . . . . . . . . 52
program counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
prologue analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
‘prologue-value.c’ . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
PROLOGUE_FIRSTLINE_OVERLAP . . . . . . . . . . . . . . . . 52
prompt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
PS_REGNUM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
pseudo-evaluation of function prologues . . . . . . . . . 3
psymtabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
PTRACE_ARG3_TYPE . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
push_dummy_call . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
push_dummy_code . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
R
raw register representation . . . . . . . . . . . . . . . . . . . 39
read_fp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
read_pc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
read_sp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
reading of symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
red zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
register data formats, converting . . . . . . . . . . . . . . 40
register groups. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
register representation. . . . . . . . . . . . . . . . . . . . . . . . 40
REGISTER_CONVERT_TO_RAW . . . . . . . . . . . . . . . . 40, 51
REGISTER_CONVERT_TO_TYPE . . . . . . . . . . . . . . . . . . 41
REGISTER_CONVERT_TO_VIRTUAL . . . . . . . . . . . . 40, 51
REGISTER_CONVERTIBLE . . . . . . . . . . . . . . . . . . . 40, 50
REGISTER_NAME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
register_reggroup_p . . . . . . . . . . . . . . . . . . . . . . . . 50
REGISTER_TO_VALUE . . . . . . . . . . . . . . . . . . . . . . 41, 50
register_type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
REGISTER_U_ADDR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
REGISTER_VIRTUAL_TYPE . . . . . . . . . . . . . . . . . . . . . 51
regset_from_core_section . . . . . . . . . . . . . . . . . . 51
regular expressions library . . . . . . . . . . . . . . . . . . . . 66
Release Branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
remote debugging support . . . . . . . . . . . . . . . . . . . . 31
REMOTE_BPT_VECTOR . . . . . . . . . . . . . . . . . . . . . . . . . . 57
representations, raw and virtual registers . . . . . . 39
representations, register and memory . . . . . . . . . . 40
requirements for gdb . . . . . . . . . . . . . . . . . . . . . . . . . . 1
restart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
running the test suite . . . . . . . . . . . . . . . . . . . . . . . . 90
Appendix B: Index
107
S
T
SAVE_DUMMY_FRAME_TOS . . . . . . . . . . . . . . . . . . . . . . . 53
SCANF_HAS_LONG_DOUBLE . . . . . . . . . . . . . . . . . . . . . 33
SDB_REG_TO_REGNUM . . . . . . . . . . . . . . . . . . . . . . . . . . 53
secondary symbol file . . . . . . . . . . . . . . . . . . . . . . . . 24
SEEK_CUR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
SEEK_SET. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
sentinel frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SENTINEL_FRAME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
separate data and code address spaces . . . . . . . . . 36
serial line support. . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
SHELL_COMMAND_CONCAT . . . . . . . . . . . . . . . . . . . . . . . 64
SHELL_FILE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
SIGWINCH_HANDLER . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
SIGWINCH_HANDLER_BODY . . . . . . . . . . . . . . . . . . . . . 32
SKIP_PERMANENT_BREAKPOINT . . . . . . . . . . . . . . . . . 54
SKIP_PROLOGUE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
SKIP_SOLIB_RESOLVER . . . . . . . . . . . . . . . . . . . . . . . . 49
SKIP_TRAMPOLINE_CODE . . . . . . . . . . . . . . . . . . . . . . . 54
SLASH_STRING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
software breakpoints . . . . . . . . . . . . . . . . . . . . . . . . . . 5
software watchpoints . . . . . . . . . . . . . . . . . . . . . . . . . . 7
SOFTWARE_SINGLE_STEP . . . . . . . . . . . . . . . . . . . . . . . 51
SOFTWARE_SINGLE_STEP_P . . . . . . . . . . . . . . . . . . . . 51
SOFUN_ADDRESS_MAYBE_MISSING . . . . . . . . . . . . . . . 51
SOLIB_ADD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
SOLIB_CREATE_INFERIOR_HOOK . . . . . . . . . . . . . . . . 64
solib_loaded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
solib_unloaded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
SOM debugging info . . . . . . . . . . . . . . . . . . . . . . . . . 28
SOM format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
source code formatting . . . . . . . . . . . . . . . . . . . . . . . 72
SP_REGNUM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
spaces, separate data and code address . . . . . . . . 36
STAB_REG_TO_REGNUM . . . . . . . . . . . . . . . . . . . . . . . . . 54
stabs debugging info . . . . . . . . . . . . . . . . . . . . . . . . . 27
stabs_argument_has_addr . . . . . . . . . . . . . . . . . . . 52
stack alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
START_INFERIOR_TRAPS_EXPECTED . . . . . . . . . . . . . 64
STEP_SKIPS_DELAY . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
STOP_SIGNAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
STOPPED_BY_WATCHPOINT. . . . . . . . . . . . . . . . . . . . . . . 8
STORE_RETURN_VALUE . . . . . . . . . . . . . . . . . . . . . . . . . 55
store_typed_address . . . . . . . . . . . . . . . . . . . . . . . . 37
struct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
struct value, converting register contents to . . 40
submitting patches . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
sym_fns structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
symbol files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
symbol lookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
symbol reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SYMBOL_RELOADING_DEFAULT . . . . . . . . . . . . . . . . . . 55
SYMBOLS_CAN_START_WITH_DOLLAR . . . . . . . . . . . . . 49
symtabs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
system dependencies . . . . . . . . . . . . . . . . . . . . . . . . . 75
table output functions. . . . . . . . . . . . . . . . . . . . . . . . 14
target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
target architecture definition. . . . . . . . . . . . . . . . . . 34
target vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
TARGET_CAN_USE_HARDWARE_WATCHPOINT. . . . . . . . . 7
target_changed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
TARGET_CHAR_BIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_CHAR_SIGNED . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_COMPLEX_BIT . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_DOUBLE_BIT . . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_DOUBLE_COMPLEX_BIT . . . . . . . . . . . . . . . . . 55
TARGET_FLOAT_BIT . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_HAS_HARDWARE_WATCHPOINTS . . . . . . . . . . . . 7
target_insert_breakpoint . . . . . . . . . . . . . . . . . . . 6
target_insert_hw_breakpoint . . . . . . . . . . . . . . . . 6
target_insert_watchpoint . . . . . . . . . . . . . . . . . . . 8
TARGET_INT_BIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_LONG_BIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_LONG_DOUBLE_BIT . . . . . . . . . . . . . . . . . . . . 55
TARGET_LONG_LONG_BIT . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_PRINT_INSN . . . . . . . . . . . . . . . . . . . . . . . . . . 56
TARGET_PTR_BIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
TARGET_READ_FP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
TARGET_READ_PC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
TARGET_READ_SP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
TARGET_REGION_OK_FOR_HW_WATCHPOINT. . . . . . . . . 8
target_remove_breakpoint . . . . . . . . . . . . . . . . . . . 6
target_remove_hw_breakpoint . . . . . . . . . . . . . . . . 6
target_remove_watchpoint . . . . . . . . . . . . . . . . . . . 8
TARGET_SHORT_BIT . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
target_stopped_data_address . . . . . . . . . . . . . . . . 8
TARGET_VIRTUAL_FRAME_POINTER . . . . . . . . . . . . . . 56
TARGET_WRITE_PC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
TCP remote support . . . . . . . . . . . . . . . . . . . . . . . . . 31
TDEPFILES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
terminal device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
test suite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
test suite organization . . . . . . . . . . . . . . . . . . . . . . . . 91
trimming language-dependent code . . . . . . . . . . . . 30
tuple output functions . . . . . . . . . . . . . . . . . . . . . . . 14
type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
type codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
U
U_REGS_OFFSET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out functions, usage examples . . . . . . . . . . . . .
ui_out_field_core_addr . . . . . . . . . . . . . . . . . . . .
ui_out_field_fmt . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_field_fmt_int . . . . . . . . . . . . . . . . . . . . . . .
ui_out_field_int . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_field_skip . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_field_stream . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_field_string . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_flush . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64
13
18
16
16
16
16
17
17
16
18
Appendix B: Index
ui_out_list_begin . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_list_end . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_message . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_stream_delete . . . . . . . . . . . . . . . . . . . . . . .
ui_out_table_begin . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_table_body . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_table_end . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_table_header . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_tuple_begin . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_tuple_end . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_out_wrap_hint . . . . . . . . . . . . . . . . . . . . . . . . . . .
ui_stream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UINT_MAX. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ULONG_MAX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
unwind_dummy_id . . . . . . . . . . . . . . . . . . . . . . . . . . . .
unwind_pc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
unwind_sp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
USE_PROC_FS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
USG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
using ui_out functions . . . . . . . . . . . . . . . . . . . . . . .
108
16
16
18
18
17
14
15
15
15
18
15
15
18
17
32
32
56
47
47
64
33
18
V
value_as_address . . . . . . . . . . . . . . . . . . . . . . . . . . .
value_from_pointer . . . . . . . . . . . . . . . . . . . . . . . . .
VALUE_TO_REGISTER . . . . . . . . . . . . . . . . . . . . . . 41,
VARIABLES_INSIDE_BLOCK . . . . . . . . . . . . . . . . . . . .
vendor branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
virtual register representation . . . . . . . . . . . . . . . . .
void . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
volatile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
37
56
57
78
39
96
34
W
watchpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
watchpoints, on x86 . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
word-addressed machines . . . . . . . . . . . . . . . . . . . . . 36
wrap_here . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
write_pc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
writing tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
X
x86 debug registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
XCOFF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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