4.9 Running a pre-processor

With -cpp on the command-line, the IDL compiler will do a `pre-wash' of the input by first running a pre-processor over it. Which pre-processor to use is determined as follows:

• If the CPP environment variable is defined, use what it is bound to as the pre-processor to invoke.
• If CPP isn't defined, the default value for it is gcc -E -x c.
• By default, the output from the pre-processor is written to a temporary file in the directory /tmp/. To put it elsewhere, set the environment variable TMPDIR.

The options -D and -U can be used to define or `undefine' CPP variables via the command line.

To use the Microsoft Visual C++ compiler as your pre-processor, set the environment variables as follows:

 CPP=cl /nologo /P
 TMPDIR=