gcc -Wp

The following program uses printf, yet without including stdio.h. Additionally, the macro FOO is not defined in the translation unit:

int main() {
    printf(FOO);
}

When the following makefile invokes gcc, it uses the -Wp option to pass the -D and -include options to the preprocessor so that FOO is defined and stdio.h included.

a.out: prog.c
	gcc -Wp,-DFOO='"Hello world\n"' -Wp,-include,stdio.h $< -o $@

GCC options