CODEWITHSUNDEEP
c++functiondeclaration
MichaelAndroidNewbie
MichaelAndroidNewbie

Reputation: 695

How does calling this function (without a definition) work?

So I am trying to get to grips with someone's code (and cannot contact them) and I do not understand why they do this. They call a function in main like this:

LOG_AddFunction();

This function is defined in a header file like this:

#define LOG_AddFunction()    LOG_Add(LOG_TYPE_NORMAL, "%s()", __FUNCTION__)

Then LOG_Add is defined in the same header file:

extern int  LOG_Add(LOG_TYPE eType, const char *pcText, ...);

There does not seem to be any ultimate definition of the LOG_AddFunction function and I do not understand why the code calls it. Can someone shed some light on this please?

Upvotes: 0

Views: 143

Answers (1)

Lightness Races in Orbit
Lightness Races in Orbit

Reputation: 385114

LOG_AddFunction is not a function. It is a function-like macro. Its only "definition" is exactly what you showed us in the question.

Its purpose is to automatically call LOG_Add with the name of the function at the callsite (__FUNCTION__) automatically passed. Whenever you write LOG_AddFunction(), those characters are automatically replaced by the preprocessor (just as with any other macro) with LOG_Add(LOG_TYPE_NORMAL, "%s()", __FUNCTION__).

This saves typing the whole LOG_Add call every time; nothing more.

Upvotes: 7

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