Question

I have test.c in which I would like to have the statement

#include "abc.h" (the header file of libabc)

only if test.c has been compiled with libabc as:

gcc test.c -labc

If test.c is simply compiled as

gcc test.c , abc.h should not be included.

How can I do that?

Answer 1

One approach is to use -D to define a macro:

gcc test.c -labc -DABC

#ifdef ABC
#include "abc.h"
#endif

If you’re running this command from Bash, then you could in principle create a shell-function wrapper around gcc to automatically add -DABC when -labc is specified:

function gcc ()
{
    local arg
    for arg in "$@" ; do
        if [[ $arg = -labc ]] ; then
            command gcc "$@" -DABC
            return
        fi
    done
    command gcc "$@"
}

. . . but I don’t really recommend that.