When you compile an application with
XL C/C++,
the compiler uses default settings that are determined in a number
of ways:
- Internally defined settings. These settings are predefined by
the compiler and you cannot change them.
- Settings defined by system environment
variables. Certain environment variables are required by the compiler;
others are optional. You might have already set some of the basic
environment variables during the installation process (for more information,
see the XL C/C++ Installation
Guide). Setting environment variables provides
a complete list of the required and optional environment variables
you can set or reset after installing the compiler, including those used for parallel processing.
- Settings defined in the compiler configuration file, vac.cfg.
The compiler requires many settings that are determined by its configuration
file. Normally, the configuration file is automatically generated
during the installation procedure. (For more information, see the ).
However, you can customize this file after installation, to specify
additional compiler options, default option settings, library search
paths, and other settings. Information on customizing
the configuration file is provided in Using custom compiler configuration files.
- Settings defined by the GCC options configuration file. If you
are using the gxlc or gxlc++ utility
to map GCC options, the default option mappings are defined in the /etc/gxlc.cfg
file. You can customize this file to suit your requirements; for more
information, see Configuring the gxlc or gxlc++ option mapping.