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What is the most significant difference of these two max operations? Which one do you prefer to use in your system, and why?

  1. #define max(a,b) (a)<(b)?(b):(a)
  2. int max (const int a, const int b) { return (a) < (b) ? (b) : (a); }

I am trying to see if I am on the right track for the above question. My first thought is obviously that the #define indicates a preprocessor directive, or MACRO, named "max". Therefore, anywhere "max" is encountered in the program, it will be replaced with the defined value of this macro. Macros also dont require any memory allocation, so we can expect faster execution times.

The const keyword, on the other hand, does require memory allocation, and is not able to be changed by the executing program. The overall consensus through my notes and some online sources seems to be that macros are more efficient/faster since they do not require the memory allocation. Therefore, it would seem I would prefer to use macros for their speed advantages.

Basically my question is, am I nailing the main differences between these two? Or am I missing something major?

Paul R
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enigma
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    Always parenthesize the RHS of your macro. Otherwise, what would be `max(1, 2) +1` ? – A.S.H Nov 09 '15 at 22:39
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    The overall consensus for C++ should be to use `std::max`. Also any speed advantage concerns from macro vs. function is a serious case of premature optimisation at work. – MicroVirus Nov 09 '15 at 22:44
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    Might want to review those notes. The difference between your two options has nothing to do with memory allocation. – Greg Hewgill Nov 09 '15 at 22:45

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