Question

I’m trying to compile the code in Visual Studio (2008) and g++.
In vs2008 it’s successful, but in g++ it reported error.
if add const,
test(const test &source):a(source.a) {}
g++ will compiled succeed.
I kown that test aa = 2; will create a temporary object and call copy-constructor.
temporary object cannot bind to a non-const reference
so,why the vs2008 can compiled it succeed?

class test{  
public:  
    test():a(1) {}  
    test(int num):a(num) {}
    test(test &source):a(source.a) {}  
private:
    int a;
};

int main(){
    test aa = 2;
    return 0;
}

Answer 1

VS has a non-standard extension that allows it, unfortunately.

There’s a compiler flag to disable extensions, but last I checked it also makes it impossible to use the standard library. Your best bet is to keep the Warning Level on 4 (though this particular situation gets no warning), and check your compilations with multiple compilers when possible.