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c++rvo

Will C++ compiler optimize return-by-value code?

Lets assume i use Visual Studio or modern GCC with -O2. Will compiler create S inside func() and then copy it to a my_result, or will it create my_result with constructor (5, 6, 5 + 6) without creating temporary S?

NOTE: Function func() definition and its usage are in separate .obj files!

struct S
{
    S(int _x, int _y, int _z) : x(_x), y(_y), z(_z) { }
    int x, y, z;
};

S func(int a, int b)
{
    return S(a, b, a + b);
}


/// USAGE ///

S my_result = func( 5, 6 );
Solution

  • Modern compilers will often optimize this kind of operation. See return value optimization