C + + function returns an example of a class object

The following example uses the compiler in Visual Studio 2012 (the Default and O2 optimization results are not the same) and g++4.7.2 (MinGW) results.

The code is as follows	Copy Code
#include <iostream> using namespace Std; Class A { Public int A; A (int i): A (i) { cout << "A ():" << a << Endl; } ~a () { cout << "~a ()" << A << Endl; } A (const a& x): A (X.A) { cout << "Copy A ()" << a << Endl; } }; A test1 () { return A (1); } A test2 () { A tmp (2); return TMP; } int main () { A A = Test1 (); A B = test2 (); cout << "Before exit" << Endl; return 0; }

As you can see, the compiler has done the relevant optimizations in the face of this situation, and the VS2012 compiler can see the copy constructor call by default.