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c++macrosinline

Mixing inline and macro functions

I've decided to try something. I know macros are evil and should be avoided but wanted to see what's going to happen if I do such a thing.

#include <iostream>
using namespace std;
inline void add(int x, int y) { cout << "Inline: " << x + y << endl; }
#define add(x,y) ( cout << "Macro: " << x + y << endl )

int main()
{
    add(3,5);
}

It outputs:

Macro: 8

If I comment out the #define line inline starts working, and the output turns into Inline: 8.

My question is, why compiler decides to use macro function instead of inline. Thank you!

I'm using Linux Mint 18.2, g++ 5.4.0, with no parameters g++ -g t2.cpp -o t2.

Solution

  • Macro substitution is performed via the pre-processor before compilation. Thus the compiler never sees add(3,5) - it only sees the macro expansion.