Comment by ARandomerDude

4 years ago

I don't quite understand these lines:

    #define ;

    #define do

I was under the impression it was "#define CNAME value" – what does it mean when there is no value? A trip to Google didn't turn up anything for me, so I'm wondering if a C master can weigh in. Thanks!

2 comments

ARandomerDude

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.

asveikau 4 years ago
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.