Function Macros

Function-like macros copy text; this example shows the expanded expression beside a safer inline function call.

function_macros.cpp

#include <iostream>

#define ADD_TEN_BAD(x) x + 10

inline int addTen(int value) {
    return value + 10;
}

int main() {
    int value = ;

    int textReplacementResult = value + 10 * 2;
    int functionResult = addTen(value) * 2;

    std::cout << "value=" << value << std::endl;
    std::cout << "textReplacementResult=" << textReplacementResult << std::endl;
    std::cout << "functionResult=" << functionResult << std::endl;
    return 0;
}

#include <iostream>

#define ADD_TEN_BAD(x) x + 10

inline int addTen(int value) {
    return value + 10;
}

int main() {
    int value = ;

    int textReplacementResult = value + 10 * 2;
    int functionResult = addTen(value) * 2;

    std::cout << "value=" << value << std::endl;
    std::cout << "textReplacementResult=" << textReplacementResult << std::endl;
    std::cout << "functionResult=" << functionResult << std::endl;
    return 0;
}

#include <iostream>

#define ADD_TEN_BAD(x) x + 10

inline int addTen(int value) {
    return value + 10;
}

int main() {
    int value = ;

    int textReplacementResult = value + 10 * 2;
    int functionResult = addTen(value) * 2;

    std::cout << "value=" << value << std::endl;
    std::cout << "textReplacementResult=" << textReplacementResult << std::endl;
    std::cout << "functionResult=" << functionResult << std::endl;
    return 0;
}

function-like macro A function-like macro can look like a function call, but the preprocessor still treats it as text replacement.