AIX Version 4.3 Differences Guide

cases, the user is free to override the environment variable with an explicit option
in the config file or the command line.
32-bit mode is invoked by specifying -q32 on the compiler command line and is
the default if OBJECT_MODE is not set. This option is equivalent to a direct
expansion into the -qarch=com option. For the compilers that do not have 64-bit
yet, use of the -q32 and/or the -q64 option will cause the following warning (this is
the usual warning on unrecognized options):
1501-055 Option -q32, -q64 is not recognized and is ignored.
Problems with #pragma arch Suboptions in Source Files
The -q32/64 option has no pragma equivalence because the compilation mode
must be determined before the compiler driver exits and invokes the compiler.
Implicitly expanded options are parsed with the rest of the command line to
produce a final compilation mode. From this compilation mode, the options are
passed separately to the compiler, linker, and assembler. However, since the
ARCH suboption has an equivalent #pragma arch suboption in the source file, the
individual files may be compiled in a different mode than what was decided by the
command line.
It was decided to disallow the setting of a #pragma arch suboption in a source
file. This is a change in Version 4.0 of the C compiler that means a loss of
backward compatibility with previous C compiler versions.
Mixed-Mode Compilation and Two-Step Compile and Linking
When you cause a mixed 32- and 64-bit compilation mode, your XCOFF objects
will not bind. This will become obvious if the compile and link occurred in one
step. However, you may not know this if the compile and link occurred in different
steps. In other words, if you compiled and produced 64-bit objects, you need to
remember to link using the 64-bit mode (when linking using xlc), otherwise the
objects will not link. If the objects are in mixed XCOFF mode, then they will never
link, and you must recompile completely, making sure that all objects will be in the
same mode.
There is a set of new configuration file attributes that are used in place of the
normal attributes whenever the compiler determines that the 64-bit mode is
enabled. These new attributes are:
• crt_64
• gcrt_64
• mcrt_64
The new definitions for these attributes are:
crt_64 Path name of the object file passed as the first parameter to the
linkage editor. If you do not specify either -p or the -pg option, the
crt_64 value is used. The default depends on the compiler being used.
gcrt_64 Path name of the object file passed as the first parameter to the
linkage editor. If you specify the -pg option, the gcrt value is used. The
default depends on the compiler being used.
mcrt_64 Path name of the object file passed as the first parameter to the
linkage editor if you have specified the -p option. The default depends
on the compiler being used.
58 AIX Version 4.3 Differences Guide