MPLAB® XC8 C Compiler Version 1.20 Release Notes - Digi-Key

MPLAB® XC8 C Compiler
Version 1.20 Release Notes
Produced on Wednesday, 12 June 2013
Previous Versions
System Requirements
Devices Supported
Editions and License Upgrades
Installation and Activation
Compiler Documentation
Customer Support
Documentation Updates
New Documents
User's Guide Clarifications and Corrections
Local Variable Qualification
Assembly Code Deviations
Device Family Macros
Disabling Optimizations
Fletcher's Algorithm
New Error/Warning Messages
What's New
Version 1.20
Version 1.12
Version 1.11
Migration Issues
Version 1.20
Version 1.12
Version 1.11
Fixed Issues
Version 1.20
Version 1.12
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Version 1.11
Known Issues
Microchip Errata
1. Overview
1.1. Introduction
This is a major update to the Microchip MPLAB® XC8 C compiler.
This compiler version introduces a significant new feature: generation of ELF/DWARF debugging files. In addition, there is new part support, and fixes to a number of reported bugs.
Previously, two HI-TECH C compilers supported Microchip 8-bit PIC devices: HI-TECH C
Compiler for PIC10/12/16 MCUs and HI-TECH C Compiler for PIC18 MCUs. MPLAB XC8
replaces both these compilers and supports all 8-bit PIC devices released as of this time.
1.2. Previous Versions
The previous version MPLAB XC8 C compiler was 1.12, released November 2012.
The last released version of HI-TECH C Compiler for PIC10/12/16 MCUs was 9.83, released in
September 2011. The previous HI-TECH C Compiler for PIC18 MCUs was 9.80, released in October 2011.
1.3. System Requirements
The MPLAB XC C compilers and the licensing software they utilize are available for a variety of
operating systems, including Microsoft Windows XP Professional SP3/Vista SP1/Windows 7
Professional; Ubuntu 9.10; or Mac OS X 10.5. The compiler may also run on the various other
Linux distributions, such as Oracle Enterprise Linux 5, Ubuntu 8.x and 10.04, Red Hat Enterprise Linux.
If you are running a license server, only computers with operating systems supported by the
compilers may be used to host the license server. The license server does not need to run on a
server version of the operating system. And specifically, Microsoft Windows Server platforms
are not supported by the compiler.
1.4. Devices Supported
This compiler supports all known 8-bit PIC devices at the time of release. See
pic_chipinfo.html (in the compiler's doc directory) for a list of all supported baseline and
mid-range devices and pic18_chipinfo.html for a list of all supported PIC18 devices. These
files also list configuration bit settings for each device.
1.5. Editions and License Upgrades
The MPLAB XC8 compiler can be activated in several different operating modes: Free, Standard
and PRO. The Standard and PRO modes are licensed modes and require a key for activation obtained after purchase. These two modes offer two levels of improved optimization features comMPLAB® XC8 C Compiler Version 1.20 Release Notes"
pared to the Free mode. A compiler operating in Free mode can be operated indefinitely without
a license. You can change to any operating mode (license permitting) from the MPLAB X IDE
project properties (or MPLAB IDE v8 Build Options) on a build-by-build basis.
The compiler can be evaluated in any licensed mode for 60 days free of charge. After the evaluation period has expired, the compiler reverts to the Free mode and the trial optimization features
are disabled.
You can choose the operating mode or choose to evaluate the compiler during the installation and
activation process.
1.6. Installation and Activation
See also the Migration Issues and Limitations sections for important information about the latest
license manager included with this compiler.
If using MPLAB IDE, be sure to install MPLAB IDE v8.10 (or later) or MPLAB X 1.2 (or later)
before installing these tools. Quit the IDE before installing the compiler. Run the .exe (Windows), .run (Linux) or .app (OS X) compiler installer application, e.g.
XC8-1.00.11403-windows.exe and follow the directions on the screen. The default installation directory is recommended. If you are using Linux, you must install the compiler using a
terminal and from a root account. Install using a Mac OS X account with administrator privileges.
The option "Update MPLAB IDE to use XC8 for existing C18 projects", if set, will change your
MPLAB IDE settings so that all existing legacy projects designated to use either MPLAB C18 or
MPLAB C Compiler for PIC18 MCUs, will, by default, use this MPLAB XC8 compiler in C18
compatibility mode. To revert this change if you select it here, you will need to manually adjust
the toolsuite settings for legacy projects that should continue to use the MPLAB C18 or MPLAB
C Compiler for PIC18 MCUs compilers. This option has no effect if you do not have legacy projects.
Activation is now carried out separately to installation. See the document License Manager for
MPLAB® XC C Compilers (DS52059) for more information.
The XC License Manager now supports roaming of floating network licenses. Aimed at mobile
users, this feature allows a floating license to go off network for a short period of time. Using
this feature, you can disconnect from the network and still use your MPLAB XC compiler. See
the doc folder of the XCLM install for more on this feature.
MPLAB X IDE v1.40 includes a Licenses window (Tools > Licenses) to visually manage roaming.
1.7. Compiler Documentation
The compiler's user's guide covers all aspects of the compiler's operation, as well as other useful
information. Check the well-populated index for your search term. A How-to chapter gives answers to common questions relating to the compiler and writing programs.
Customer Support
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Common problems are explained in the FAQ list. You can also ask questions of other users of
this product in the XC8 Forum.
Microchip welcomes bug reports, suggestions or comments regarding this compiler version.
Please direct any bug reports or feature requests via the Support System.
At times, advisory message 1395 may be issued by the compiler. This message is part of a new
testing process. The compiler will display this message if it encounters a specific code sequence
that results in internal compiler templates being used in a unique way. This message does not imply a bug in the generated code; however, the code sequence encountered could be used to further improve the compiler's performance. If you wish to participate by contributing the code that
generated this message, you are welcome to send the project to Support; otherwise, you may ignore this message.
2. Documentation Updates
2.1. New Documents
The user's guide associated with this 1.20 version has been updated. The guide details new compiler features and expands the description of some existing features.
A PDF version of the PIC18 peripheral library document has been added to the compiler docs
directory. This indicates those functions which are relevant to each device and the library interface.
2.2. User's Guide Clarifications and Corrections
The following sections provide additional information to that found in the user's guide shipped
with the compiler.
2.2.1. Checksums
The information contained in the user's guide relating to the generation of checksum values (Sections: 4.8.17 --CHECKSUM: Calculate a Checksum and -CK) does not clearly indicate
that when selecting any of the Fletcher algorithms, this selection overrides any width specified.
Algorithm 7 (Fletcher 8) will always reserve 2 words for the checksum value; Algorithm 8
(Fletcher 16) will reserve 4 words for the checksum value.
2.2.2. Local Variable Qualification
In sections Near Type Qualifier and Far Type Qualifier, they indicate that auto
objects cannot use either the near or far specifiers. This text should indicate that all local variables, even static local objects, cannot use the near or far specifiers. The same objects also
cannot be made absolute (see Section Absolute Variables in Data Memory).
Assembly Code Deviations
Section 6.4.1 Assembly Instruction Deviations does not list the format for the index form of the
MOVIW and MOVWI instructions. MPLAB XC8 uses the form:
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
for both instructions.
2.2.4. Device Family Macros
When compiling for PIC18 devices, a macro that indicates the device family is defined by the
compiler. For example, when compiling for a PIC18F2610, the corresponding family macro defined is _18F2X1X_FAMILY_. To determine the family macro relevant to your device, turn on
verbose compilation and observe the -D options passed to the preprocess, cpp. Alternatively, you
may look for the FAMILY field in the picc-18.ini file in the compiler's dat directory.
Disabling Optimizations
The user's guide indicates that the --OPT option (or the MPLAB X IDE project properties
equivalent widget) can be used to disable optimizations. Note that in order to disable intrinsic
features of OCG, you must also run the compiler in Free mode. Not all OCG features can be disabled.
2.2.6. Fletcher's Algorithm
The code for the fletcher 16-bit algorithm indicated in the user's guide contains a return statement that should not be present. The extraneous statement is towards the end of the fletcher16
function and is marked and bolded in the following:
sumB = (sumB & 0xFFFF) + (sumB>>16);
return sumB << 16 | sum;
// remove me
sumB <<= 16;
2.3. New Error/Warning Messages
The following message is not present in the compiler's user's guide.
1457 local variable "*" cannot be make absolute (Code Generator)
You cannot specify the address of any local variable, whether it be an auto, parameter or
static local object.
int pushState(int a) {
int cnt __at(0x100);
// oops -- you cannot specify an address
3. What's New
The following are new features the compiler now supports. The version number in the subheadings indicates the first compiler version to support the features that follow.
3.1. Version 1.20
New Device Support The following parts are now fully supported by this release: PIC16F1704,
PIC16LF1704, PIC16F1708, and PIC16LF1708.
ELF/DWARF Debugging Previously, COFF debug files were produced to allow source-level
debugging in MPLAB IDE. The compiler can now produce ELF/DWARF files, although
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
the default output format is still COFF. ELF/DWARF files are not compatible with
MPLAB IDE v8 but will be the preferred format if you are using MPLAB X IDE as they
have fewer limitations. You must be using a version of MPLAB X IDE that supports this
file format for the MPLAB XC8 compiler. Not all aspects of DWARF are implemented in
this compiler release. See the Known Issues section for more details.
New Free mode optimizations The assembler's jump-to-jump optimizations, which previously
was only available with a licensed compiler operating mode, is now available in Free
mode. By default, this optimization is disabled, but it can be enabled from the --OPT option or the Optimization category in MPLAB X IDE in the usual way. If enabled, this optimization reduced the size of code output by the compiler.
New language extension option A new driver option --EXT can be set to cci, iar or xc8 to
indicate that the C language extensions accepted by the compiler are those belonging to the
Common C Interface, IAR compatibility mode, or the native XC8 syntax, respectively. All
of these extensions are discussed in the user's guide.
Expanded hardware multiply usage The PIC18 hardware multiply instructions are now used
for 16x16 bit integer multiplication. The library routine that implements this feature breaks
the multiplication into several operations that can use the 8-bit hardware multiply instruction. The 32-bit integer multiplication routines continue to use an iterative solution and do
not use these instructions.
New listing option Previously a C list file was produced for each C source file being compiled.
If an assembly list file was request (which is the default in MPLAB IDE) then these listing
files were overwritten with the assembly listing content. The C listing files are no longer
produced by default. If you would like C listing files to be generated, a new option
--CLIST has been added to request this action.
3.2. Version 1.12
New Device Support The following parts are now fully supported by this release: MCP19114,
MCP19115, PIC16LF1824T39A, PIC16F570, PIC16F753 and PIC16HV753.
3.3. Version 1.11
New Device Support The following parts are now fully supported by this release: PIC16F1788,
PIC16F1789, PIC16LF1788 and PIC16LF1789.
New peripheral libraries The following devices (and their LF counterparts) now have peripheral library support: PIC18F45K50, PIC18F24K50 and PIC18F25K50. The peripheral libraries for all supported devices have been updated to the latest code base.
New parsing option A new driver option has been added that alters the generation of intermediate files produced by the parser. The option is --PARSER and can be set to lean or rich.
The lean suboption (the default) will not include unused symbols in intermediate files.
These are included when selecting the rich suboption, but not that this setting will generate
larger intermediate (p-code) files and will slow down the compilation considerably. The
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
operation of prior versions of the compiler was equivalent to the rich setting. Use the
rich setting if you need unused symbols to be included in the link stage.
New enhanced mid-range errata workaround The compiler now has the ability to employ an
errata workaround for some enhanced mid-range devices. This is controlled by the --ERRATA option (CLOCKSW), which is used to control other PIC18 errata workarounds. The
workaround will affect the device startup code, but is not enabled by default. Check your
device literature to see if this workaround should be enabled.
3.4. Version 1.10
New device support The following parts are now fully supported by this release: MCP19110,
MCP19111, RF675F, RF675H, RF675K, PIC12F529T39A, PIC12F529T48A,
PIC12LF1840T39A, PIC12LF1552, PIC16F527, PIC16F1454, PIC16LF1454,
PIC16F1455, PIC16LF1455, PIC16F1459, PIC16LF1459, PIC16F1784, PIC16LF1784,
PIC16F1786, PIC16LF1786, PIC16F1787, PIC16LF1787, PIC18F45K50, PIC18F24K50,
PIC18F25K50, PIC18LF45K50, PIC18LF24K50, PIC18LF25K50, PIC18F97J94,
PIC18F87J94, PIC18F67J94, PIC18F96J94, PIC18F86J94, PIC18F66J94, PIC18F95J94,
PIC18F65J94, PIC18F85J94, PIC18F96J99, PIC18F86J99, PIC18F66J99.
The Common C Interface (CCI) The Common C Interface is a documented set of ANSI standard refinements, non-standard extensions and guidelines to help you write code which is
more portable across all MPLAB XC C compilers. A new chapter has been added to the
XC8 User's Guide describing these features.
User's guide A new compiler user's guide has been included with this release. See the Documentation Updates section, above, for more information.
Roam-out Licensing A new “roam out” feature allows a network license to be checked out for
an extended period for use on a particular computer. While the license is checked out, the
computer has licensed use to an XC compiler, and need not be in contact with the network
license server. When the license is returned to the network license server, it is once more
available to be used as a floating license, or to be roamed out to other computers.
Psect allocation The CCI __section() specifier can also be used in non-CCI mode. Refer to
the CCI chapter in the user's guide. It can be used in place of the #pragma psect directive.
Function and module information Information about each function, which appears in the assembly list file, is now also displayed in the map file. In addition, a summary of program
memory usage on a module-by-module basis is shown in the map file. This allows an estimate of the size of the code (excluding data) being generated by each module.
Bank specification with PIC18 devices The qualifiers bank0 through bank3 may now be used
with PIC18 devices to allocate variables to a specific memory bank. These qualifiers must
be used with the --ADDRQUAL option.
Implementation of strftime function The strftime() function has been implemented and is
available in the standard libraries.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Qualifier synonyms A side effect of the CCI features is that when not in CCI or strict ANSI
mode, most of the non-standard specifiers, e.g. bit, near and far, can also be represented
with two leading underscores, as in __bit, __near and __far etc.
SFR structure types The structures that are defined to represent SFRs are now a typedef type
that is available for general use.
Function in-lining A new qualifier, inline, can be applied to some C functions. A call to any
function, thus qualified, will not generate a call-return sequence, but will be replaced by
the assembly code associated with the function body. This expansion will save stack usage
and may reduce code size if the function body is small. The assembler has always had the
ability to inline small assembly sequences, so code size reductions may not be large. The
operation of this qualifier is similar to use of the new #pragma inline directive. The
previous (version 1.00 and earlier) inline pragma implementation has been renamed to
instrinsic. (See Migration Issues below.)
Assembly psect flags To support function inlining, two new psect flags have been added: inline and keep. These indicate to the assembler, respectively, that the contents of a psect
may be inlined (and then removed), and that the contents of a psect may be inlined but
must never be removed.
3.5. Version 1.01
Enhanced PIC optimizations New optimizations, specifically aimed at the enhanced mid-range
PIC devices, have been added. These optimizations reduce code size and target any code
that indirectly accesses locations via the FSR registers.
3.6. Version 1.00
Psect merging and splitting Two new PSECT directive flags have been added to allow splitting
or merging of psects by the assembler optimizer. Now, by default, no splitting or merging
takes place, but the use of the split=allow and merge=allow flags can indicate that
these optimizations can take place. See the assembly language chapter in the user's guide.
Unified 8-bit device support This compiler unifies the two former HI-TECH C compilers which
previously supported Microchip 8-bit PIC devices: HI-TECH C Compiler for PIC10/12/16
MCUs and HI-TECH C Compiler for PIC18 MCUs. This MPLAB XC8 compiler supports
compilation for any supported 8-bit PIC device from the one application. A single device
driver, xc8, is used to invoke the compiler regardless of the target device. This driver will
invoke the appropriate internal applications based on your device selection. The picc and
picc18 drivers which controlled the former compilers are currently still employed, and the
baseline/mid-range and PIC18 code generator and assembler applications are still separate.
Only one copy of the generic applications, such as the preprocessor (cpp), the parser (p1),
the linker (hlink), and utilities like hexmate, objtohex and cromwell are included with
the compiler, and these are shared by all device targets.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Operating modes The former HI-TECH C Compiler for PIC18 MCUs only operated in a Lite or
PRO mode. With XC8, a Free (previously called Lite), Standard and PRO mode are available for all target devices.
4. Migration Issues
The following are features that are now handled differently by the compiler. These changes may
require modification to your source code if porting code to this compiler version. The version
number in the subheadings indicates the first compiler version to support the changes that follow.
4.1. Version 1.20
-G option disable The option that controlled generation of symbol files has been disabled. This
option was always selected in MPLAB IDE and there was never a need to disable this feature. Symbol files are now always produced. You can continue to specify this option in
builds, but it will be silently ignored.
C listings disabled by default C listing files are no longer produced by default. See the New
listing option (in New Features) entry for more information.
Space number for EEPROM changed The space number used by psects that hold EEPROM
data has changed from 2 to 3. This only affects PIC10/12/16 devices. This will not affect
most projects, but if you see an error indicating memory space redefined: 03/02,
then look for hand-written assembly that defines a psect used to hold EEPROM data and
change the space value.
Warnings for absolute local objects (XC8-652) Previously the compiler would silently ignore
any local (defined inside a function) object which the user had attempted to make absolute.
The compiler will now issue a warning to say that the address specification will be ignored.
Warnings for qualified local objects (XC8-670) Objects which are local to a function (including autos and static local objects) cannot be qualified as far or near. The compiler was
not indicating that the specifier was being ignored. A warning is now issued for such definitions.
4.2. Version 1.12
Access of multi-byte SFRs When writing literal values to multibyte volatile SFRs, the compiler will write high order byte first, then the low order byte. This conforms to the requirements of some PIC SFRs, such as the NCO register, which must be written in a particular
order. This write order is not guaranteed for other expressions.
Watchdog configuration bit Some devices have had their configuration bit setting change from
WDTEN to WDT. For these devices you will need to update any #pragma config directives
that specify this setting.
Implicit function in-lining The implicit in-lining of function performed as an assembler optimization is now disabled by default. The assembler optimizer has, in the past, in-lined small
assembly routines as part of its optimizations. You can re-enable it using the driver option
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
-A-auto_inline. This change does not affect in-lining of C functions, controlled using
the inline specifier.
4.3. Version 1.11
Inline SFR names When referencing SFR names specified in <xc.h> from in-line assembly
code, do not use a leading underscore character with the symbol. So, for example, use the
symbols PORTA or RA0_bit in in-line assembly code. (The same is true for SFR symbols
in assembly modules that include <>; however, the bit symbols have different
names, for example, PORTA and RA0.) See the user's guide for more information on assembly code and accessing SFRs.
Compiler banner information The information shown in the compiler banner printed with each
compilation has changed. The compiler operating mode is no longer printed, but you can
still find this information in the list file. The license manage will now return and print the
license type.
Unused symbol inclusion Unused symbols are no longer included in intermediate p-code files.
This should not affect most customers. See the What's New section for information on the
new --PARSER option which allows unused symbols to be included in the final link step.
Pointer comparison warning Warning number 1413 "*" is positioned at address 0x0
and has had its address taken; pointer comparisons may be invalid
should now only be issued for symbols that are user-defined and not for temporary variables, such as "ROM" or "RAM".
Specification of config pragma The arguments to the #pragma config can now be quoted.
You may prefer to quote the setting-value pairs to ensure that the preprocessor does not
perform substitution of these tokens, e.g., #pragma config "BOREN=OFF"
4.4. Version 1.10
Re-activation of the compiler As of version 1.10, the license files used by the XC compiler license manager are installed in a different location. This is automatically handled by the
installer; however, if you plan to use an older license file with v1.10, you will need to reactivate the v1.10 XC8 compiler with your activation key before you can use it. Previously,
the installers could find older license files and did not require re-activation. Re-activation
will not be necessary in future when updating compiler versions.
PIC10/12/16 Assembly Header Files The names of some of the assembly header files have
changed. Provided code included the generic and recommended <> assembly
header file, then this will be transparent. Specifically, changes relate to using the extension
.inc instead of .h for assembly-domain header files; the names of device-specific assembly header files now match their C-domain counterparts.
Deprecation of in-line assembly header files The PIC10/12/16 header files that were usable
from assembly that was in-line with C code have been remove. These header files were
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
previously included via the generic file <caspic.h>. The content of these files will be included once you include <xc.h> in your C source code.
Removal of single-letter bit definitions The definitions for SFR bits that used a single letter
identifier have been removed, for example the SSP1CON register bit S. These register bits
are still available in the corresponding SFR structures, for example SSP1CONbits.S. The
absence of these very poorly chosen identifiers should not be missed.
4.5. Version 1.01
Missing SFR definitions There have been changes to the header files to ensure correlation with
the data sheet. This may resulted in some SFR definitions being no longer available. If you
see undefined symbol errors or other build errors relating to SFR names, please refer to the
appropriate device-specific header file and update your code.
The inline pragma The much misused inline pragma has been changed. What was the inline pragma is now known as the intrinsic pragma. Since the inline pragma was not
intended to be used with user-defined routines, this should have no impact on existing projects. Use of the inline pragma in this compiler version will be ignored; however, future
versions may implement a user-operable inlining feature.
Filling unused values The --FILL option, which is used to fill unused memory locations, now
assumes the value specified is a 2 byte word. Previously the size of this value was the same
as the target device program memory addressability i.e. 1 for PIC10/12/16 devices and 2
for PIC18 devices. The width of the value can always be specified with the option. See the
user's guide section relating to hexmate.
4.6. Version 1.00
Library functions removed The following library functions and macros are now longer supported and have been removed from the libraries and header files.
• checksum8 and the macro CHECKSUM8
• checksum16 and the macro CHECKSUM16
• checksum32 and the macro CHECKSUM32
Any attempt to use these will result in a compiler error.
Memory functions replaced by peripheral library equivalents Flash and EEPROM functions
and macros have been removed from the compiler libraries and header files. They have
been replaced with those in the peripheral library.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Compiler drivers While you may continue to call the picc or picc18 command-line drivers, it
is recommended that projects be swapped to use the unified xc8 driver. Future compiler
releases may discontinue the device-specific drivers or additional functionality may be
added to xc8 that will not be usable if you continue to use the device-specific drivers.
FN-type directives All FN-type directives are no longer supported and should not be used. Such
directive include: FNBREAK, FNSIZE, FNROOT etc. The FNCALL and FNROOT directives are
still issued by the compiler, but it is recommended that these not be used in handwritten
assembly code.
5. Fixed Issues
The following are corrections that have been made to the compiler. These may fix bugs in the
generated code or alter the operation of the compiler to that which was intended or specified by
the user's guide. The version number in the subheadings indicates the first compiler version to
contain fixes for the issues that follow. The bracketed label(s) in the title are that issue's identification in the tracking database. These may be of benefit if you need to contact support.
5.1. Version 1.20
Bad conditional code (XC8-640) An error in an assembler optimization that dealt with a bittest-and-skip instructions and FSR manipulations caused the sense of some conditional
control statements to be inverted.
Phase errors (XC8-590, XC8-691, XC8-49) The assembler optimizer was removing redundant
page selection instructions, but other parts of the assembler where not taking this into account. This created a mismatch in expected and actual sizes of some jump instructions
which led to phase errors being produced. This issue affected hand-written and compilergenerated assembly code.
Absolute function placement (XC8-203) The address specified for functions made absolute
was rounded down to the nearest 0x10 value. So, for example, if you attempted to place a
function at address 0x56, it was actually located at address 0x50. This only affected programs compiled for PIC18 devices.
Missing errata NOP instructions (XC8-692) The assembler was not correctly adding in NOP
instructions that form part of the fetch errata workarounds for some PIC18 devices. (See
the user's guide --ERRATA option section for more information.) Delay routines that required these instructions were known to run too fast. A consequence of this fix is that code
size will increase for devices that require the fetch errata workarounds.
Wrong UINT24_MAX value (XC8-565) The value for this <stdint.h> macro was higher by
1 than it should have been.
Bad variable access after calls (XC8-694) The compiler was, on occasion, placing a bank selection instruction before the call to a routine. This bank selection was not properly being
tracked and may have resulted in incorrect access of objects once in the called function.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Assertion failure using --ROM or --RAM options (XC8-517) When attempting to reserving
memory that was outside your target device's on-chip memory, these options may have
caused an assertion failure.
Invalid access via pointer (XC8-643) In some situations, the compiler was not detecting that
the upper TBLPTR register was being changed from its assumed state. As a result, code
that dereferenced a pointer with both RAM and ROM targets may have corrupted this register and triggered a subsequent failure in the code.
Assembler crash with bad options (XC8-510) If options were passed directly to the assembler
application but no file names were present, the assembler issued an error and continued
processing. The error produced in this situation is now a fatal error to prevent the crash.
This issue would have only affected users driving the assembler directly.
Assembler crash when specifying functions as inline (XC8-589) In some instances, when a
function was declared inline the assembler crashed.
Can't Generate Code message associated with unused objects (XC8-636) In cases where a
pointer was not used but was assigned the address of an object, this message may have
been emitted. Optimizations associated with such code are now restricted and the message
will not be issued.
Parser crash with enumerated types (XC8-637) The parser may have crashed when scanning
code associated with enumerated types. This may have been associated with taking the address of enumerated objects.
Qualifiers silently ignored for local objects (XC8-670) Objects which are local to a function
(including auto and static local objects) cannot be qualified as far or near. The compiler
was not indicating that the specifier was being ignored. A warning is now issued for such
Absolute addresses silently ignored for local objects (XC8-652) Objects which are local to a
function (including auto and static local objects) cannot be made absolute. The compiler
was not indicating that the @ or __at() construct was being ignored. A warning is now issued for such definitions.
Linear memory allocation of objects (XC8-501) Absolute objects that specified a linear memory address may not have been allocated correctly if the object's equivalent banked addresses mapped into the common memory. This only affected enhanced mid-range devices
and objects that were not large enough to be automatically allocated to linear memory. The
compiler now correctly allocates these objects.
Identical case label values in a switch statement (XC8-493) The compiler was not detecting
the use of more than one identical case label value inside a switch() statement. This is
now correctly identified and will trigger an error.
__DEVICENAME__ not defined (XC8-659) This predefined macro was not being defined by
the compiler. This is now defined unconditionally.
Procedural abstraction of in-line assembly code (XC8-660) The assembler optimizer was performing procedural abstraction on assembly code that was placed in-line with C code. The
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
optimizer should not perform any optimization of in-line assembly code. The optimizer has
been prevented from performing these optimizations.
BSR register not recognized by regsused pragma (XC8-663) Any attempt to list the BSR register in the regsused pragma would have resulted in an error. This has been corrected and
this register may now be used with this pragma for those devices that implement this register.
Allocation of PIC18 far variables (XC8-582) In some instances, far-qualified variables may
have been linked at address 0, not in the memory defined as the far RAM.
Indexing array with constant expression failure (XC8-648) With enhanced mid-range devices
only, any operation that involved adding a integer constant to an address (typically this will
be an array access with a constant integer index) may have caused subsequent code to fail.
Such code was not correctly reporting its use of WREG.
Initialization of large objects on enhanced mid-range device (XC8-672) Initialization of large
objects (such as arrays or structures) that contained a pointer may not have been assigned
the appropriate values by the runtime startup code. This only affected PIC16F1xxx devices.
Uninitialized const objects not assigned zero (XC8-553) If const objects were not initialized,
they were not being automatically assigned the value 0 by the compiler. These objects had
no memory reserved for them at all and this may have resulted in them appearing to overlap with other const objects. This is now corrected; any const object that does not have
an initial value is implicitly assigned 0 by the compiler.
Assertion failure reserving RAM (XC8-662) In some instances, reserving RAM when using
any non-enhanced mid-range part using the --RAM option would result in an assertion failure hi >= lo.
Integers allowed with specifiers (XC8-549) The integer constants usable with specifiers such as
__at() were limited to 16-bit values. These values can now be specified as 32-bit values.
Multiply defined symbols (XC8-516) If code used the __section() specifier with variables,
there may have been symbols contained in the runtime startup code that were defined more
than once, producing an error. (Such symbols might be clear_ram or clrloop, for example.) This duplication has been corrected.
__mediumconst symbol undefined (XC8-621) In some circumstances, particularly when using
the peripheral library, the compiler may have produced an undefined symbol error for
Functions not inlined (XC8-521) When a function qualified as inline was called from
main(), it was never inlined and a regular call was made. Inlining should now take placed
for any suitably qualified function called from main().
Incorrect return instruction (XC8-525) For some baseline devices (most notably the
12F529T39A and 12F529T48A), the compiler may have attempted to use the non-existent
RETURN instruction instead of a RETLW instruction.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Partial access to ID locations (UDBC-678) The compiler did not allow access to the entire ID
location for devices that implement this memory as being 14-bits wide (e.g., the
PIC16F1503). This has been corrected and you may now program all the bits of these ID
Code failure accessing absolute objects straddling a bank (XC8-601) The wrong bank may
have been selected when accessing absolute objects that straddle a bank boundary. Code
may have failed when accessing the addresses in banks following that of the bank of the
object's base address.
5.2. Version 1.12
Compile times and crash (XC8-127) A sorting issue related to pointer variables may have significantly increased the compilation time of projects. Not all projects were affected by this
issue. This issue may also have caused the code generator to run out of memory, or even
crash in some situations.
Compile times (XC8-498) A further issue affecting compilation times was corrected. This issue
affected the assembler when --ASMLIST was used. (This option is on by default when using the IDE.)
Installer operation The installer program was not correctly setting the write permissions for
some files. This was reported on Windows XP, but may have affected other platforms.
Bank selection issue (XC8-494) In an expression such as:
A = B + C;
where A and C are unsigned 16-bit objects in different banks and B is an unsigned
char, a bank select instruction may have been omitted resulting is the wrong value being
assigned to the destination variable.
5.3. Version 1.11
Compilation times (XC8-441) Large projects, particularly those targeting PIC18 devices, may
have experienced increased compilation times. This was due to the compiler processing
more symbols. A new option has been added, and enabled by default, to limit the symbol
list. The new option is --PARSER. See the New Features section for more information.
Looping around pointGraphComplete() Error (XC8-442) A non-deterministic pointer-related
issue was causing this error to be printed, and terminating compilation.
Debugging absolute objects (XC8-447) Some SFRs and absolute addressed objects residing in
RAM would appear as being located in program memory during a MPLAB X or v8 debugging session. The content of these values would, thus, be incorrect. Absolute symbols
should now appear to be located in their correct memory space and their contents shown
Parsing of config pragma arguments (XC8-452) The parsing of arguments to the #pragma
config directive was erratic when it came to quoted arguments. The quote character ' " ' is
now a token delimiter and you may quote the arguments to this pragma, e.g. "WDTEN=ON"
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Doing so will avoid any macro substitutions by the preprocessor. If you have defined macros for ON, OFF or any other token used by the config pragma, consider quoting the
pragma arguments or moving the pragmas to a module that is not exposed to your macros.
Incorrect access of array of strings (XC8-454) Code which used a variable to access an element of a string array may have failed when the index was non-zero.
Unsupported short long message using CCI (XC8-429) When using the CCI, a warning may
have been issued indicating that the short long type was not supported. The header files
that referenced this type have been updated and use a plain long type when compiling for
the CCI.
Undefined symbols with bitwise operations (XC8-424) Some bitwise operations, for example
| or &, when used in functions that were in the interrupt call graph, may have produced
code that contained references to undefined temporary symbols. Such symbols would look
similar to i2u49_41.
Can't generate code with printing floats (XC8-108) For some placeholders associated with
float types, a can't generate code error may have been triggered with (s)printf. This
has been corrected.
Detection of incomplete types (XC8-109) The parser was not detecting definitions using incomplete types, for example:
typedef struct foo foo_t;
foo_t x;
// where foo has not been defined
Code which is defined in such a way will now trigger an error from the parser.
Can't generate code for library string routines (XC8-413) Some string library functions may
have caused "can't generate code errors". These have been adjusted to ensure correct compilation.
Assignment to volatile bytes (XC8-427) In some operating mode, when assigning '1' to a
volatile byte variable, it may not have been updated atomically (with one write rather
than clear and increment instruction). This problem did not affect absolute objects and may
have only caused runtime problems if the byte was accessed from main code and interrupt.
--ROM option The --ROM option was not processing its arguments correctly which may have
resulted in it not reserving the memory specified.
5.4. Version 1.10
Using far with Functions (XC8-337) If the far qualifier was used with functions, it confused
the compiler into thinking the function identifier was that of a variable destined for RAM.
This may have triggered an error, if no far memory was defined, or caused a runtime code
Non-functional --ADDRQUAL option (XC8-293) The reject suboption of this option was
not working correctly for PIC10/12/16 device. The require and request suboptions
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
were not working correctly for PIC18 devices. This option should now work as expected
for all devices.
Conversion of integer to bit-field (XC8-353) The compiler was treating single-bit bit-fields as a
boolean rather than an integer quantity when it came to assignment. Code that assigned a
byte or larger integer to a single-bit bit-field may have failed.
Can't Generate Code for Duplicated Functions (XC8-358) The compiler may have issued
Can't Generate Code error messages in situations where a function was duplicated in interrupt and main-line code and this function used pointers.
Handling of incomplete types (XC8-374) The parser was producing incorrect type information
where a type used in a declaration was, at that point, incomplete, e.g. if you used a structure tag in a declaration, but that tag had not been defined. The code generator would subsequently crash if such incomplete type information was encountered. types should always
be defined before they are used, but the compiler will no longer crash on such situations.
Testing of volatile bytes (XC8-388) The code that tested volatile bytes variables for (in)equality was using a MOVF x,f instruction. This was not in keeping with the spirit of the
volatile keyword and could also play havoc with certain registers, such as the TMR0
register, on some baseline devices, such as the 10F222, which require a read delay after
being written. This code sequence is no longer used and access of SFRs will be well behaved.
Pointer assignment failure (XC8-342, XC8-343) In some circumstances, assignment of a structure member address to a pointer may have resulted in an incorrect destination pointer size
being determined by the compiler. This would have resulted in subsequent pointer dereferences being invalid. This problem was detected only with assignments to pointer parameters as part of a function call, but could have potentially occurred elsewhere.
Pointer access failure with duplicated functions (XC8-377) If a function that has a pointer parameter is called from main-line and interrupt code (i.e. it is duplicated by the code generator), the compiler may have issued a "looping around allocGlobals", or "can't generate
code" error message. In other situations, the code may have compiled, but accesses to the
pointer may have been incorrect. The issue could have affected any device with interrupts.
Undefined btemp symbol (XC8-371) In some circumstances, exacerbated by the use of a debugger and devices with small amounts of RAM, the internal compiler symbol btemp may
not have been defined and an error results. This symbol is now correctly defined.
Incorrect access of high program memory (XC8-363) The compiler was not correctly setting
the TBLPTRU register for accesses of absolute-addressed const data located above
0xFFFF in PIC18 program memory.
Incorrect configuration bit/user ID settings (XC8-385) Attempts to program the configuration
bit or user ID settings may have failed due to a sorting bug that may have resulted in the
bits being programmed in the wrong order. The issue was inconsistent, but could affect all
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Improved error relating to IDLOC (XC8-384) If non-hex digits were used in for any nibble in
the IDLOC() macro a confusing error was issued. A new message (#1436) has been created
for this situation.
5.5. Version 1.01
Looping around allocGlobals error (XC8-318) This error may have been triggered, but is not
specific to any particular code sequence. The compiler has been updated to ensure this
trigger will not result in this error.
Access of char arrays (XC8-304) If the index expression used with an array of char consists of
a non-constant expression (e.g. a plain variable) from which is subtracted a constant (e.g.
myArray[idx-1]), then the index calculation may have been incorrect and the wrong
element accessed. This issue mostly affected PIC18 devices and arrays no larger than a
bank. It may have affected enhanced mid-range parts with array sizes larger than 256 bytes.
The issue has been resolved for all devices.
Code jumps to wrong location (XC8-295) If the assembler optimizer is enabled, assembly code
that directly wrote to the program counter may have been abstracted which may have
caused a jump to the wrong location and code failure. C code affected would produce a
lookup table of some description, but it unlikely that C code would trigger this issue. Handwritten assembly would only be affected if the option to optimize assembly source files
was enabled.
Duplicated SFRs (XC8-319) Some SFR bit-field structures had duplicate entries in the devicespecific header files and have been removed.
Bit objects on baseline devices Uninitialized global bit objects may not have been zeroed for
baseline devices, and in some instances, the generated startup code may have corrupted
other memory locations or caused the device to restart.
Call graph inconsistencies The call depth of some functions was not correctly indicated in the
call graph shown in the assembly list file. The total amount of auto, parameter and temporary variable usage was also incorrectly displayed for some functions in the call graph.
Wide bit-fields in header files (XC8-289) Some header files were being generated with SFR
bit-fields that were wider than a byte. This is not allowed by the compiler. Such definitions
are no longer contained in the header files.
Wrong external memory access (XC8-286) The --EMI options was not correctly being processed and this may have meant that access to external memory may have been incorrect.
Only several PIC18 devices have such memory.
Error on assembly directives after including header file (XC8-285) After including the header file into assembly code, some assembly directives, e.g. the DS directive,
may have generated an error. This was due to SFR names conflicting with the directive's
name. The header files will on longer use any SFR name that conflicts with a directive.
This will mean that SFR names may not always match those listed in the device data sheet.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Bad access at start of function (XC8-94) The code at the beginning of function could have accessed the wrong address (bank) for a variable if the compiled stack was built up over multiple banks and WREG was used to pass a function argument.
Incorrect RAM ranges with 12F1501 (XC8-274) The RAM ranges associated with this device
did not reserve the memory from 50-6F. Allocation of user-defined objects to this memory
may have caused code failure.
Bad results with 24-bit expressions (XC8-227) The code generated for some arithmetic and
bitwise operations involving 24-bit integers were missing some necessary bank selections
which may have generated wrong results.
Compiler crash with conditional operator (XC8-117) Assigning a pointer the result of an expression using nested conditional statements could have caused the compiler to crash for
PIC18 devices.
Bad results with long arithmetic (XC8-241) The results of some long arithmetic expressions
may not be correctly assigned due to a bank selection bug.
Build errors in MPLAB X IDE (XC8-101, XC8-104) Source file paths that contained spaces
were being written to the dependency files without the spaces escaped. This resulted in
these files containing erroneous targets and dependancies which may have resulted in incorrect builds. In addition, the preprocessor would generating a dependency file for assembly modules incorrectly assuming that the intermediate file to have a ".p1" extension and
not ".obj" resulting in the same behavior.
Crash with compiler-domain symbols (XC8-18) User-define variables and functions should
never start with an underscore character as such symbols are in the compiler's domain. Inappropriate use of these symbols in a program, however, was leading to a compiler crash.
The crash no longer will occur; however, you should continue to avoid using symbols beginning with an underscore.
MPLAB X IDE plugin Previously the XC8 MPLAB IDE plugin overwrote the HI-TECH Universal Plugin such that the universal plugin no longer appeared in the toolsuite list. This is
no longer the case. The XC8 v1.01 installer will install and reinstate both the XC8 and universal plugins so that they will both be selectable from the IDE.
Bad if() code (XC8-58) In some instances the assembler optimizer would incorrectly move
MOVLW instructions which could cause some logical expressions (such as those used by if
statements) to be incorrectly evaluated.
Not honoring message disable (XC8-62) When compiling for PIC10/12/16 targets the assembler was not honoring the --MSGDISABLE option. Thus, it was impossible to disable warning messages produced by this application. This issue did not affect other applications or
any application when compiling for PIC18 targets.
Bad call to subtype() Error (XC8-73) In some instances where a function has a pointer type as
its first parameter but the function is never called, a "bad call to typeSub()" error may occur.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Incorrect optimizations involving carry bit (XC8-77) The assembly optimizer may have incorrectly moved instructions that set the carry bit above other code that would subsequently
clear carry before it was being used.
Bad optimization of indirect access (XC8-95) In some situations, expressions with the form
*ptr = *ptr op A; may fail. In particular it is the optimization of assignmentoperations when the destination is an indirect access which can lead to incorrect results.
Bad right shift code (XC8-105) In some instances for PIC18 targets, the code generated for
right-shift a signed long operand would access the wrong file registers, giving an incorrect result.
Memory reservation using --CODEOFFSET (XC8-230) This option should have reserved
memory in all linker classes associated with program memory. It was only reserving this
memory from the CODE class but not for other classes that hold const objects. This was
unlikely to cause issues since const objects are typically not allocated to low address; however, all classes are now adjusted.
Badly optimized if() code (XC8-75) The assembler optimizer may have procedurally abstracted
code that erroneously contained return-style instructions. This may have caused code such
as if() statements to be ignored and fail. This has now been corrected.
Redundant MOVLP instructions (XC8-49) Redundant MOVLP instructions were being produced for some call sequences for Enhanced mid-range devices.
5.6. Version 1.00
Bogus warning on -B option (XC8-11) If compiling under MPLAB v8, in some instances a
warning indicating that the -B option was defunct was issued. This option is indeed defunct, but the compiler has been adjusted so that this is not produced when compiling under the IDE.
Parser crash (PICC18-618) If an unexpected attribute was used with function definitions, e.g.
__attribute__ ((const)), the parser crashed instead of giving an error. This has now
been corrected.
Parser crash (PICC-684, PICC-688, PICC18-596, PICC18-607, PICC18-616, PICC18-619,
PICC18-620, PICC18-621) In some circumstances, the parser would crash when encountering illegal or unusual source code. This has been seen with code that accesses some
structure members, passing malformed arguments to functions, or with non-prototyped
(K&R) function definitions. Changes to the parser should prevent the application crashing.
Bad code associated with negation (PICC-652) In certain cases, negating a 16-bit integer may
have overwritten WREG. This has been corrected.
Crash on structure with no members (PICC-597) If a structure was defined that had no members, the parser application crashed. This has been rectified.
Arrays of structures in MPLAB not watchable (PICC-544, PICC18-593) In some circumstances, the watch window in MPLAB IDE v8 would show elements of a structure array
correctly. Changes have been made to the compiler output to correct this.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Redirecting function using psect pragma (PICC-514) There were instances where use of the
#pragma psect would not appear to work as the name of the psect being redirected was
changing as a result of psect merging by the assembler optimizer. A new system of identifying mergable and splittable psects was introduced, which will assist in reducing this
MPLAB IDE popup about source code using #include (PICC18-565, PICC18-566) If you
are using any of the printf family of functions, an MPLAB IDE popup may have appeared
warning that "The project contains source files that use the #include directive from within a
function to include source code". Although this would not have affected normal debugging
operations in this particular instance, the trigger for message has been adjusted so that this
message will no longer be produced.
Zeroing of config bits (PICC18-600) If you used the PIC18 pragma to program only the lower
byte of a configuration location, the compiler may have zeroed the upper byte rather than
use the default configuration value. Ideally, all configuration words should be specified in
your programs or the --RUNTIME option to program the device with the default config
words should be enabled. However, this zeroing of he upper byte will no longer occur.
Undefined symbol with empty loops (PICC18-524) The compiler an remove some condition
code if the state of variables used in the controlling expressions are know. In some instances, where the true or false statements were an empty loop (e.g. while), the compiler
may have deleted a label that was still being referenced by other code. This would have
produced an undefined symbol, which might look something like l9.
Crash with undefined functions (PICC18-532) If function that were not defined were assigned
as the target of a function pointer, the compiler may have crashed. This crash has been
fixed and now the linker will report the symbols as being undefined, as expected.
Errors indicated in unused files (PICC-428) When an error indicating a variable is too large is
emitted, the name of the file that contained the variable definition may have indicated a
source file that was not in the project, such as a library file.
Assignment to structure ignored (PICC-433) In situations where an assignment is made to a
structure is followed by an assignment to a bitfield within that structure, the initial assignment may be removed. This would only occur in PRO mode. This has now been fixed and
the compiler notes the distinction between the objects accessed.
Compiler crash and old library modules (PICC-573) The compiler may have crashed is some
library modules were used from the SOURCES directory of the compiler. This directory no
longer include files from non-OCG compilers, as they are not compatible to OCG compilers and will not compile.
Undefined ?Fake symbol (PICC-589, PICC-581) This error may have occurred for code that
indirectly called a external function defined in assembly code or was part of another build.
Only functions that returned a value in memory would be affected by this issue. The error
is no longer produce, but you are required to define a symbol that represents the memory
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
location where the return value will be stored. See the User's Guide on External Functions
for more information.
Linker crash with assembler optimizers (PICC-648) If the assembler optimizers (psect merging) were enabled, in some situations the linker would crash if a psect was removed but
was still referenced by a directive. This has been corrected and all assembly optimizations
may be employed.
Compiler crash with bad memory ranges (PICC-608) If a memory range was specified using
the --RAM option, or its equivalent in MPLAB IDE, and that range was excessively large,
the compiler my have produced an assertion failure. In such situations, the compiler now
prints a more informative error.
Cromwell error with MCPxxxx targets (PICC-642) If compiling for an MCP device, an error
relating to the "prefix list" would have been triggered. This has been corrected and compilation can be performed for these devices.
Cromwell crash (PICC-493) Cromwell may have crashed if encountering information generated from static bit objects that are absolute.
Crash with malformed warning pragma (PICC-610) If the message number(s) were omitted
from the #pragma warning disable directive, the compiler crashed. An error is now
emitted if this situation is encountered.
Read of write-only registers (PICC-658) If an attempt was made to read a Baseline device
write-only register, e.g. TRIS, the compiler would produce a can't generate code error message. A more specific message is now produced alerting you to the offending operation.
Can't generate code (PICC-683, PICC-499) The compiler was not able to generate code for
some expressions involving logical or bitwise operation on bit objects. This has been corrected.
Prototype for eeprom_write (PICC-675) The prototype for eeprom_write incorrectly stated
that this function returned a value. This was not correct and the prototype now indicates a
return type of void.
CLRWDT appearing in _delay output (PICC-460) For some delay values, the _delay in-line
function for PIC18 targets only produced CLRWDT instructions as part of the delay. This has
been corrected and a NOP is used instead. For PIC18 targets, you have a choice of _delay
or _delaywdt to implement in-line delays, which do not use and use, respectively, the
CLRWDT instruction as part of the delay.
Optimization of volatile bits (PICC-606) The compiler was not generating the appropriate information to prevent the assembler optimizer from optimizing access to volatile bit objects.
Although the code would have been functionally correct, subsequent optimizations may
have caused runtime failures. This correct information is now generated and volatile bit
access will not be optimized unexpectedly.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
vprintf and vsprintf linker errors (PICC-524, PICC-619) Trying to use either of these functions may have resulted in the undefined symbols __doprint, _vprintf or _vsprintf.
These routines are now fully supported in the libraries and can be called.
Upper bound of mktime (PICC18-126) The mktime function had a upper limit of the year
2020; higher values would return incorrect results. This limit has now been extended to the
year 2038.
Bad call to subtype with regsused pragma (PICC18-392) If using the regsused pragma for a
function before the definition of that function, this error occurred. This has been corrected
and the pragma can be used at any point in the source code.
Looping around allocGlobals error (PICC-570) This error may have occurred in some situations, particularly when NULL pointers were being assigned in the source code. This has
been corrected.
Read of wrong array element (PICC-542) When reading a const array using a constant index,
in some situations, the wrong element may be read. This bug did not affect array access
using a variable or other expression as the index.
Memory allocation An improved memory allocation scheme is used when variables are qualified as being in a particular bank or near and the --ADDRQUAL option is set to require. This
will reduce the likelihood of Can't find space errors from the linker.
Code generator crash with undefined functions (PICC18-532) If a function pointer was assigned the address of a function that is defined in external code, the code generator may
have crashed. External functions might include those defined in assembly source code.
This only affect PIC18 targets.
Can't generate code errors with nested structures (PICC-628) This error may have occurred
for code that accessed bit-fields within structures that themselves were members of other
No stack allocated to function error (PICC-611, PICC-485, PICC-416, PICC-637) This error
is now unlikely to be triggered by code. It was most likely to occur with complex expressions, particularly involving floating-point arithmetic.
Can't generate code errors with short long types (PICC-632) Some assignment operations on
short long types, e.g. |=, &= and *= etc may have triggered a "can't generate code" error
when compiling for baseline or mid-range parts. The ability to generate code for such expressions has been enhanced.
Parser crash with bad identifiers (PICC-622) The parser (p1) may have crashed if certain
keywords were used as a variable identifier, e.g. if you were to try to define a variable with
the name eeprom. A crash may also have occurred if reserved keywords were used in place
of variables in expressions. The crash has been corrected, but variable identifiers cannot be
reserved keywords.
Symbol defined more than once for in-line assembly (PICC-563) If the REPT macro was
specified in in-line assembly, the code generator was generating additional labels multiple
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
times. This triggered an error indicating the symbol was defined more than once. This has
been corrected and REPT can safely be used in in-line assembly code.
RAM ranges for 16(L)F1507 The RAM ranges available when selecting this device extended
further than the physical device implementation. This has been corrected.
6. Known Issues
The following are limitations in the compiler's operation. These may be general coding restrictions, or deviations from information contained in the user's manual. The bracketed label(s) in
the title are that issue's identification in the tracking database. This may be of benefit if you need
to contact support.
ELF debugging issues Not all aspects of the ELF/DWARF debugging file have been implemented in this compiler release. Only MPLAB X IDE supports ELF, but you must ensure
that you are using a version of this IDE that can process ELF files produced by the compiler. The following are some of the issues that may not work as expected.
• Unused variables will not be identified in the ELF file.
• Constant propagation optimizations may affect which variables are watchable in the IDE or
the values that are indicated in the Watch window.
• In-line C functions will not be debuggable.
• Procedural abstraction will affect the operation of breakpoints.
• Variables residing in both memory and registers may not be correctly displayed in the
Watch window.
• Nested pointers may not be dereferenced correctly in the watch window, hence the values
in reported in the Watch window will therefore be erroneous.
• Variables located in external memory will not be displayed correctly in the Watch window.
• In the Watch window the type name (as opposed to the object's name) that appears for a
anonymous structure or union typedef or an enumerated typedef will be ".".
• In the Watch window the type name displayed for an identifier that was declared using a
typedef type will be the identifier's semantic type rather than its typedef type.
Use of __section() specifier If you use the __section() specifier when defining an object,
you must also use the same specifier with any declaration of the same object. Failure to do
so may result in the specifier being ignored.
Support for scanf functions The compiler does not directly support any of the scanf-family
functions, such as scanf, sscanf, vscanf, etc., and they are not compiled into the library
files. Example source code for some of these functions can be found in the compiler's
sources directory. These examples have not been verified to work on all devices and
should be used with caution. Consider modifying this code to suite your application.
Redirecting bss variables If the #pragma psect directive is used to redirect objects that normally reside in any of the bss psects, the runtime startup code will not be aware of this and
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
will clear the memory that the variables would have ordinarily be allocated. At such an
early stage, this should not affect program execution, but if all bss objects are redirected, an
undefined symbol error will occur with PIC18 devices. Consider using the __section()
No support for vsprintf (XC8-425) This function is not supported in the compiler libraries.
Previous attempts to use it would have resulted in undefined symbol errors. This function
is now flagged as unsupported and its use will trigger an error to that effect.
Installer execution On both Mac OS X and Linux, it is necessary to run the installer as root or
with superuser privileges (using sudo, for example). If the installer is started without superuser privileges on Mac OS X, it will exit and display an informative message. In the same
situation on Linux, the installer will fail when it attempts to write to directories for which it
does not have adequate rights. The messages displayed will relate to these access failures.
For correct operation, run the installer via sudo, or as the root user, on these systems.
PATH environment variable On Linux systems, the installer, by default, updates the PATH environment variable to include paths to the new executables being installed. If the installer is
run via sudo, the default action will update the PATH variable of the user executing the
sudo command. If the installer is run by root, the installer will only update root's PATH
variable, and not the PATH variables of ordinary users. If installing the compiler while
logged in as root, a better choice is to update all user PATH variables. Alternatively, skip the
step to update the PATH variable in the installer, and to update the PATH variables of users
who will use the software, manually.
C18 code compatibility The C18 code compatibility feature is only a beta implementation. Legacy C18 projects may not compile, or compile with runtime errors when using XC8.
Changing toolsuite in MPLAB IDE v8 If the toolsuite associated with an MPLAB IDE v8 project is changed from the HI-TECH Universal toolsuite to the XC8 toolsuite, or vice versa,
the selected options in the original toolsuite are not copied over to the new toolsuite. Please
note all options before you switch and confirm the options in the new toolsuite.
IDE plugin overwrite (XC8-360, XC8-367) If an older compiler is installed after installing a
newer compiler, the new IDE plugin may be overwritten. (The 1.01 compiler installer is
known to overwrite the 1.10 plugin.) You can manually reinstall the new plugin without
having to reinstall the compiler. Run the command:
regsvr32 "C:\Path_to\microchip\xc8\v1.10\bin\MPLABXC8.dll"
for example, replacing the path with that appropriate for your compiler installation.
Call to empty function after comparison (XC8-398) Code which calls a function containing no
statements (an empty definition) which is preceded by an if() statement may fail for
16F1xxx parts. If the assembler optimizer is enabled, the call to the empty function, or subsequent code may fail. Adding any code, such as NOP();, to the empty function is enough
to work around this issue.
Assignment to pointer member of a union (XC8-341) For PIC18 devices and when the compiler is operating in PRO mode, assignment of an address to a pointer that is a member of a
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
union which in turn is part of a structure may fail if the member is accessed via structure
pointer a in the following example.
strPtr->myStruct.myUnion.myPtr = mySrcPtr;
Functions returning pointers (XC8-344) If a function returns a pointer, the size of this pointer
is larger than 1 byte, and also larger than the total size of all the parameters passed to this
function, then the memory used by the return value may not be allocated. The function's
return value may overwrite other local variables and lead to code failure. Consider adding a
dummy parameter to the function with the same size as the return value type.
PIC12F529T39A/T48A memory restrictions The previous limitation which restricted memory
to the first 4 RAM banks for user-defined variables has been lifted. Note, however, that the
compiler will not allow you to define objects that span multiple banks on these devices.
In-line delay values The delay value specified with the in-line delay function (_delay) is limited to 179,200 on PIC18 devices. With PIC10/12/16 devices, this value may be up to
In-line delays On PIC10/12/16 targets, the only in-line delay function implemented is _delay.
This uses NOP instructions, when required, as part of the delay sequence. There is currently
no equivalent version of this function that uses the CLRWDT instruction. The function, _delaywdt which is available for PIC18 targets, does use the CLRWDT instruction.
Watching const values in MPLAB v8 MPLAB IDE v8 cannot correctly display in the Watch
view any object qualified as const and stored as RETLW instructions in memory. Any const
object compiled for a PIC18 device will be observable, and this issue does not affect
Use of hardware multiply The PIC18 hardware multiply instruction is not used for any 32-bit
multiply operations. A library multiply routine is used for such operations. The hardware
multiply instruction is used for 8- and 16-bit multiplication.
Disabling function duplication (XC8-3) The interrupt_level pragma current does not prevent duplication of functions called from both main-line and interrupt code.
Psect pragma and data psects As described in the manual, the #pragma psect directive
should not be used to move initialized variables that would normally be located in one of
the 'data' psects. The initial values in program memory and space for the variables themselves in RAM must be built up in a strict order. Using this pragma will violate this assumption. Consider using the __section() specifier.
In-line assembly and labels Functions which are called from both main-line and interrupt code
should not contain in-line assembly that defines assembly labels. Such labels will not be
assigned the usual duplication prefix (i1, i2 etc) and will result in multiply-defined symbol errors.
Bank qualifiers Only bankx qualifiers for data banks 0 through 3 are supported by the compiler.
(These are enabled using the --ADDRQUAL option). Use absolute variables to place objects
in other banks, if required.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Memory Report for Absolute Variables If the user defines absolute variables (variables placed
at an absolute address via the @ construct), and any of these variables overlap other variables in memory, the compiler will also count overlapping variables when it comes to reporting on memory usage. That is, if two, byte-sized variables are located at the same address, the report will indicate 2 bytes being used, rather than 1.
Out of bound variables in watch view If variables are defined for Enhanced Mid-range devices
that are large and placed in the linear memory space, MPLAB IDE v8 shows these objects
are being "out of bound". This is display issue and is not indicative of code failure.
Variables shown in wrong memory space If an object is made absolute and allocated address 0,
it may only be visible in the program memory view of MPLAB IDE v8. This is purely an
IDE view issue and does not impact on the code operation.
Wrong watch values MPLAB IDE v8 may show incorrect values for pointers and any object
located after a pointer in a structure. The COFF debug format used by this IDE does not
allow the compiler to specify the necessary size information for pointer variables. The
compiler makes pointers a certain size based on their usage, whereas the IDE assumes all
pointers are one fixed size. This can make viewing pointers "hit and miss". Any attempt to
examine pointers in the IDE's Watch view may result in incorrect values being shown, or
an "invalid" message being displayed in the view. In addition, if a pointer is a member of a
structure, any member (of any type) located after the pointer in the structure’s memory may
also be shown incorrectly in the Watch window. The actual contents of the pointer and program execution are not affected. If you are using MPLAB X IDE, then use the new ELF/
DWARF debug format, as this allows accurate size information to be specified and will
eliminate the issue.
Switch strategies There is only one possible switch strategy currently available for PIC18 devices. It uses the space switch type. New strategies will be introduced in future compiler
versions so that PIC18 devices have similar options to the baseline/mid-range devices.
Copying compiler header files The header files shipped with the compiler are specific to that
compiler version. Future compiler versions may ship with modified header files. If you
copy compiler header files into your project, particularly if you modify these files, be
aware that they may not be compatible with future versions of the compiler.
SFRs for 12LF1840T48A The following are inconsistent in this device's header file.
• DACNSS bit not defined in DACCON0 register (118h)
• SSP1M0, SSP1M1, SSP1M2, SSP1M3, SSPEN, SSP1OV defined as SSPM0, SSPM1, SSPM2,
SSPM3, SSPEN, SSPOV in SSP1CON1 register (215h)
SFRs for 16(L)F1507 The following are inconsistent in this device's header file.
• In NCO1ACCU (49Ah) NCO1ACC<23:20> not defined
• CWG1ASD register (695h) defined as CWG1CON2
Initialization of eeprom arrays Initialization of large arrays that are qualified eeprom may fail
on enhanced mid-range devices. When the size of these arrays exceeds the size of the free
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
space in each GP RAM bank, the compiler tries to allocate the array to the linear RAM
space, not EEPROM. Small arrays are not affected by this issue.
Initialization of auto structures Structures which are auto cannot be initialized. Simply define
the structure and assign values separately.
EEPROM variable limitations There are some limitations to using variables qualified as eeprom, aside from them being not supported at all on PIC18 devices. Avoid using these
variables in complicated expressions and remember that code which accesses such objects
is complex and very slow.
Size of EEPROM arrays Arrays that qualified as eeprom and which are initialized may not
have all initial values written to the EEPROM.
Constant index into int array If a constant is used as the index into an array of const int type,
the element read may be incorrect. This issue does not affect arrays of different types, or
when the index is a variable.
Absolute initialized variables Variables which are absolute and which are not const cannot be
initialized. The following example will not generate an error, but will not work as expected. Define the variable as absolute and initialize it in main-line code.
unsigned int varname @ 0x0200=0x40; // will not work as expected
Stack overflow When the managed stack is used (the stackcall suboption to the --RUNTIME
option is enabled) in some situations the stack may overflow leading to code failure. With
this option enabled, if a function call would normally overflow the stack, the compiler will
automatically swap to using a lookup table method of calling the function to avoid the
overflow. However, if these functions are indirect function calls (made via a pointer) the
compiler will actually encode them using a regular call instruction and when these calls
return, the stack will overflow. The managed stack works as expected for all direct function
calls, and for all indirect calls that do not exceed the stack depth.
Main function size If the function main produces assembly code that is 0x1FF words long, this
cannot be placed in the program memory and a "can't find space" error message is produced. Increasing or decreasing the size of the function will allow it to be positioned correctly and the error will not be displayed. This only affects Baseline PIC devices.
Functions called from in-line assembly The code generator will not be able to identify a C
function called only from in-line assembly code if the definition for that C function is
placed before the assembly call instruction in the source file. Placing the function definition after the call is acceptable. If the function cannot be identified, no code will be generated for the function and the linker will issue undefined symbol errors.
Can't Generate Code messages When compiling for baseline devices, some complex expressions may cause compile-time errors (712) Can't generate code for this expression. The expressions should be simplified to work around this. This may require the use of additional
variables to store intermediate results. This is most likely with long integer or floatingpoint arithmetic and particularly those devices with less than 4 bytes of common memory
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Indirect function calls The parameters to functions called indirectly via a pointer may not be
passed correctly if the following conditions are met.
• A function is called indirectly from both main-line and interrupt code
• This function has parameters
• The function pointer used to call this function is also assigned the address of other functions at some point in the program; and
• This function pointer is initialized when it is defined.
All other instances of indirectly calling a function, even from interrupt and main-line code,
will work as expected.
option and tris For baseline devices, the OPTION and TRIS registers must be written as a byte.
Writing individual bits is not supported.
PIC17 support PIC 17 devices (for example, 17C756) is not supported by this compiler.
fast32 floats The option to select the fast 32-bit float or double library for PIC17 devices that
was included in the PICC STD compiler is no longer available.
Procedural abstraction An instance has been seen, but not resolved, which appears to be related
to the procedural abstraction optimization of the assembler. If suspect behavior is encountered, compiling for speed, instead of space, will disable this optimization and allow you to
confirm if this is the underlying cause. This problem was reported for an Enhanced Midrange device.
Pointer assignments In PRO mode, if a pointer assignment is made where one of the pointers is
a member of a structure, the compiler may fail to copy the whole pointer, causing the
pointer to register an incorrect address.
Configuration words (PIC18 parts only) The new device support introduced in PICC18 v9.80
will not automatically program the default values into the configuration words when no
value is specified. If your project does not program all configuration words explicitly, select the option "Program the device with default config words" in the Linker tab.
Specifying configuration words on PIC10/12/16 devices The __PROG_CONFIG() and __CONFIG() macros can be used to specify the configuration words on PIC10/12/16 devices as
well as PIC18 devices. The __PROG_CONFIG() macro must use a literal constant argument; you cannot use the configuration setting symbols with this macro. The __CONFIG()
macro must only use the predefined configuration setting symbols and you may not not use
a literal value with this macro.
MPLAB 8 debugging information When compiling projects with multiple C files, MPLAB
may throw up a warning dialog with the message beginning "The project contains source
files that use the #include directive from within a function to include source code." This is
due to the Omniscient Code Generation in the XC8 compiler, which can make multiple
source files appear in the one COF output. It does not affect the operation of the actual project.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Selecting compiler mode When using the Free version of the XC8 compiler, the ability to select
compilation modes in the plugin is disabled. If you switch to an older version of the compiler inside the MPLAB 8 plugin, you will not be able to change the compilation mode to
Standard or PRO. To work around this behavior, close the plugin, then reopen it. This
should allow other compilation modes to be selected.
rfPIC12 parts To use the rfPIC12 parts, for example the rfPIC12C509AF, you will need to specify to the compiler a part name in a format similar to RF509AF, for example. You can also
use an alias like 12C509AF, for example. The full part name is also not appropriate when
compiling from MPLAB IDE.
MPLAB IDE integration If Compiler is to be used from MPLAB IDE, then you must install
MPLAB IDE prior to installing Compiler.
7. Microchip Errata
For 8-bit PIC devices, this release of the XC8 compiler recognizes the published silicon errata
issues listed in the table below. Some of these issues have been corrected and no longer apply in
recent silicon revisions. Refer to Microchip's device errata documents for details on which issues
are still pertinent for your silicon revision. The compiler's chip configuration file records which
issues are applicable to each device. Specific errata workarounds can be selectively enabled or
disabled via the driver's --ERRATA command line option. All these errata are PIC18 specific, except for the CLOCKSW errata, which applies to enhanced mid-range devices.
Workaround details
Execution of some flow control operations may yield unexpected results when instructions vector code execution across the 4000h address
Each block of program code
is not allowed to grow over
the 4000h address boundary.
Additional NOP instructions
are inserted at prescribed locations.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Workaround details
If a high-priority interrupt
occurs during a two-cycle
instruction which modifies
fast- interrupt return mechanism (via shadow registers)
will restore the value held by
the register before the instruction.
Additional code reloads the
shadow registers with the correct values of WREG,
Using the LFSR instruction
to load a value into a specified FSR register may also
corrupt a RAM location.
The compiler will load FSR
registers without using the
LFSR instruction.
Table read operations above
the user program space
(>1FFFFFh) may yield erroneous results at the extreme
low end of the device’s rated
temperature range (-40o C).
Affected library sources employ additional NOP instructions at pre- scribed locations.
A GOTO instruction placed at Additional NOP instruction
the reset vector may not exe- inserted at reset vector if folcute.
lowing instruction is GOTO
Peripheral flags may be erroneously affected if the BSR
register holds the value 15,
and an instruction is executed
that holds the value C9h in its
8 least significant bits.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Compiler avoids generating
MOVLB 15 instructions. A
warning is issued if this instruction is detected.
Workaround details
The DAW instruction may
improperly clear the CARRY
bit (STATUS<0>) when executed.
The compiler is not affected
by this issue.
When reading EEPROM, the
contents of the EEDATA register may become corrupted
in the second instruction cycle after setting the RD bit
read EEDATA immediately.
The result returned from an
EEPROM read operation can
be corrupted if the RD bit is
set immediately following the
loading of the EEADR register.
The compiler is not affected
by this issue.
Writes to EEPROM memory
may not succeed if the internal voltage reference is not
No workaround applied
Writes to program memory
may not succeed if the internal voltage reference is not
No workaround applied
If a peripheral interrupt occurs during a TBLWT operation, data can be corrupted.
Library routine flash_write()
will temporarily disable all
applicable interrupt-enable
bits before execution of a
TBLWT instruction.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"
Workaround details
Self write operations initiated
from and acting upon a range
within the same side of the
4000h boundary may fail
based on sequences of instructions executed following
the write.
No workaround applied
Data in a RAM location can
become corrupted if an asynchronous reset (e.g. WDT,
MCLR event) occurs during a
write operation to that location.
A warning will be issued if
the length nvram psect is
greater than zero bytes (persistent variables populate this
Instruction fetches can become corrupted after certain
code sequences.
A NOP instruction as added
after TBLRD instructions,
returns, destinations of calls
and gotos, and ISR vector
An instruction may be corrupted when switching from
INTOSC to an external clock
source. (Enhanced mid-range
Switch to high-power mode
immediately after reset.
MPLAB® XC8 C Compiler Version 1.20 Release Notes"