Question about #define

[Benoit]

Hi,

	For my app I need to know if it run on Mac OS X or on GNUstep. First I 
wanted to determine it at runtime but it seems more easy to do it at 
compilation time (well it's open source after all).

	I download the source code of GNUmail and look how it is done. I found 
a lot of "#ifdef MACOSX" but I never found where is done the #define 
MACOSX.

        Where is it done ???

        TIA.

Benoit Astruc