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Asked: 2026-05-10T15:14:05+00:00

The C preprocessor is justifiably feared and shunned by the C++ community. In-lined functions,

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The C preprocessor is justifiably feared and shunned by the C++ community. In-lined functions, consts and templates are usually a safer and superior alternative to a #define.

The following macro: 

#define SUCCEEDED(hr) ((HRESULT)(hr) >= 0)

is in no way superior to the type safe:

inline bool succeeded(int hr) { return hr >= 0; }

But macros do have their place, please list the uses you find for macros that you can’t do without the preprocessor.

Please put each use-cases in a seperate answer so it can be voted up and if you know of how to achieve one of the answers without the preprosessor point out how in that answer’s comments.

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1 Answer

  1. As wrappers for debug functions, to automatically pass things like __FILE__, __LINE__, etc:

    #ifdef ( DEBUG ) #define M_DebugLog( msg )  std::cout << __FILE__ << ":" << __LINE__ << ": " << msg #else #define M_DebugLog( msg ) #endif

    Since C++20 the magic type std::source_location can however be used instead of __LINE__ and __FILE__ to implement an analogue as a normal function (template).

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