C Preprocessor testing definedness of multiple macros

c c-preprocessor logical-operators preprocessor-directive
Lefteris picture Lefteris · Jun 8, 2009 · Viewed 20.2k times · Source

I searched the site but did not find the answer I was looking for so here is a really quick question.

I am trying to do something like that :

#ifdef _WIN32 || _WIN64
     #include <conio.h>
#endif

How can I do such a thing? I know that _WIN32 is defined for both 32 and 64 bit windows so I would be okay with either for windows detection. I am more interested in whether I can use logical operators like that with preprocessor directives, and if yes how, since the above does not work.

Compiling with gcc I get :

warning: extra tokens at end of #ifdef directive , and it basically just takes the first MACRO and ignores the rest.

Answer

Aaron Maenpaa picture Aaron Maenpaa · Jun 8, 2009

Try:

#if defined(_WIN32) || defined(_WIN64)
// do stuff
#endif

The defined macro tests whether or not a name is defined and lets you apply logical operators to the result.

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