Configuring compiler defaults

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.
• Settings defined in the compiler configuration file, xlc.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 XL C/C++ Installation Guide. 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.