XL Fortran Enterprise Edition for AIX : User's Guide - IBM

Default Bit Mode
The AIX operating system 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:
Table 16. 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
Specification of the following options on the command line or in the configuration
file overrides the default option set:
v -q64
v -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. Instead, you can always use the -q32 or
-q64 option to specify the bit mode.
Module Support
64-bit support is provided in the Fortran module files that are shipped with XL
Fortran. The 64-bit and 32-bit Fortran modules are shipped in the
/usr/lpp/xlf/include directory.
Using XL Fortran in a 64-Bit Environment 285