Question

I feel, every time I read a C or C++ program, that half or more of it is just macros. I understand that macros can be cool but they are hard to track, debug, etc. Not to mention that most programming languages do not even define something like macros (although Perl6 will have something of the sort).

I personally always have found a way to write my code without using macros, whether it be with templates, multiple inheritance, etc. I have even felt I am not a good programmer because all the pros use macros and I try to avoid them as much as I can.

The question is, are there problems which cannot be solved without macros? Are macros ultimately a good/bad practice? When should I consider using a macro?

Answer 1

Yes, here’s one. When you need to add tracing code to your program in such a way that one configuration contains it and the other completely omits you have to use macros.

Something like:

#ifdef WITH_LOGGING
    #define LOG( x ) DoLog( x )
#else
    #define LOG( x )
#endif

now you use it this way:

LOG( L"Calling blahblahblah with " + getSomeStringHardToCompute() );

and in the configuration with WITH_LOGGING you have that code and otherwise it is completely omitted – not even present in the binary, and therefore

• it doesn’t help others analyze your program
• you get a smaller binary
• the program doesn’t waste time fo logging at all
• the compiler can produce better optimized code.