C Preprocessor testing definedness of multiple macros

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.

I think it should be possible this way:

#if defined block1 || defined block2 /*or any other boolean operator*/
   /*Code*/
#endif

More information here

You must use #if and special operator defined

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