User's Guide

Default Bit Mode

AIX 4.3 provides support for the OBJECT_MODE environment variable to enable the user to obtain a 64-bit development environment. AIX tools use the setting of OBJECT_MODE to determine the type of object to be used or created. The OBJECT_MODE environment variable has three recognized settings:

OBJECT_MODE=32: Works with 32-bit objects.
OBJECT_MODE=64: Works with 64-bit objects.
OBJECT_MODE=32_64: Works with either 32-bit or 64-bit objects.

The XL Fortran compiler determines the default bit mode through the setting of the OBJECT_MODE environment variable at the time of invocation. The following table shows the default bit mode and options that are set for each setting of the OBJECT_MODE environment variable:

Figure 18. Default bit mode determined by the setting of OBJECT_MODE

OBJECT_MODE Setting Default Bit Mode Default Option Set
unset 32-bit -q32
32 32-bit -q32
64 64-bit -q64
32_64 Not permitted n/a

OBJECT_MODE Setting	Default Bit Mode	Default Option Set
unset	32-bit	-q32
32	32-bit	-q32
64	64-bit	-q64
32_64	Not permitted	n/a

Specification of the following options on the command line or in the configuration file overrides the default option set:

-q64
-q32

Important Note
Using OBJECT_MODE to determine the default bit mode can have serious implications if you are not aware of the setting of OBJECT_MODE at the time of invocation. For example, you may not be aware that OBJECT_MODE has been set to 64 and you may unexpectedly obtain 64-bit object files. We strongly urge you to be aware of the setting of OBJECT_MODE at all times and to set OBJECT_MODE yourself to ensure that the compiler is invoked for the correct bit mode.

Important Note

Using OBJECT_MODE to determine the default bit mode can have serious implications if you are not aware of the setting of OBJECT_MODE at the time of invocation. For example, you may not be aware that OBJECT_MODE has been set to 64 and you may unexpectedly obtain 64-bit object files.

We strongly urge you to be aware of the setting of OBJECT_MODE at all times and to set OBJECT_MODE yourself to ensure that the compiler is invoked for the correct bit mode.

Module Support

64-bit support is provided in the Fortran module files that are shipped with XL Fortran. The 64-bit Fortran modules have the same names as the 32-bit Fortran modules, and are shipped in a separate directory, /usr/lpp/xlf/include_64.