Comment by cperciva

4 years ago

It defines those to a value of "", effectively stripping them from the source code.

The most common place where this sort of thing occurs is the common idiom

    #ifdef DEBUG
    #define debug(...) realdebug(__VA_ARGS__)
    #else
    #define debug(...)
    #endif

which allows you to sprinkle debug() calls through your code and have them disappear if you compile without defining the macro DEBUG.

1 comment

cperciva

Of course for your quoted use it's more common to see:

    #define debug(...) ((void)0)

This forces you to use debug() as a statement. If no value is defined you could omit the semicolon on a debug() statement and it still compiles.