Fixed bug #176 [I'm fixing this for the public headers, but I'm not going to bother for the SDL library code (yet)] To clarify: Normaly, GCC (or, to be precise, the preprocessor) will ignore this, and compile the code happily. However, one can specify -Wundef to get a warning about this. One can probably argue whether to consider this a bug or not; but I think that (a) from a semantic point of view, using "#if FOO" when FOO is not defined is strange, and (b) since it is possible to trigger a warning about this, and a trivial fix exists, it should be corrected. I can think of two alternative patches, BTW: 1) Simply use #define HAVE_FOO 0, instead of not defining HAVE_FOO at all 2) Change #if HAVE_FOO to #if HAVE_FOO+0 which always does the right thing. But I think I still prefer the attached patch :-).