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Date: Wed, 30 Dec 2009 08:17:52 +0100
Message-ID: <6b4b2d2c0912292317h7c4d9bbfo196dcf48396e0afa@mail.gmail.com>
From: Oliver Mahmoudi <olivermahmoudi@gmail.com>
To: "freebsd-questions@FreeBSD.org" <freebsd-questions@freebsd.org>
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Subject: how does the C pre-processor interface with make?
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X-List-Received-Date: Wed, 30 Dec 2009 07:17:58 -0000

Hey folks,

I was wondering how the C pre-processor interfaces with make. Let's suppose
that I have a little C program, something along the lines of:

#include <stdio.h>

int
main()
{
#ifdef FOO
     fprintf(stdout, "Hi, my name is foo.\n");
#endif

#ifdef BAR
     fprintf(stdout, "Hi, my name is bar.\n");
#endif

     fprintf(stdout, "I am always here.\n");

     return(1-1);
}

It is easy to control the pre-processor in the above code by defining the
respective terms or leaving them out, however,
I am trying to control the conditionals from out of a makefile.

This is essentially the way in which the kernel sources are compiled.

Any suggestions?

Thanks

Oliver