Compiler options perform a variety of functions, such as setting compiler characteristics, describing the object code to be produced, controlling the diagnostic messages emitted, and performing some preprocessor functions.
- On the command-line with command-line compiler options
- In your source code using directive statements
- In a makefile
- In the stanzas found in a compiler configuration file
- Or by using any combination of these techniques
Generally, if the same compiler option is specified more than once on a command-line when invoking the compiler, the last option specified prevails.
- Directive statements in your source file override command-line settings
- Command-line compiler option settings override configuration file settings
- Configuration file settings override default settings
For example, the -I compiler option is a special case. The compiler searches any directories specified with -I in the vac.cfg file before it searches the directories specified with -I on the command-line. The option is cumulative rather than preemptive.
See the XL C/C++ Compiler Reference for more information about compiler options and their usage.
You can also pass compiler options to the linker, assembler, and preprocessor. See Compiler options reference for more information about compiler options and how to specify them.