confused by C++ logical OR (||) operator [duplicate]

Question

Suppose I have two expressions left/right of || operator. I find if left expression is true, the right operator will never be called. For example, in my below code, when getRand returns true, I found Foo will never be called. I tested on XCode on Mac OSX, and wondering if it is a reliable feature of C++ we could rely on -- if left part of || is true, right part will never be called, or it is a special feature just for specific platform (e.g. OSX with XCode)? Post my code below, thanks.

bool Foo()
{
    std::cout << "I am called!\n";
    return false;
}

bool getRand()
{
    int random_variable = std::rand();
    std::cout << random_variable << '\n';

    return random_variable % 2 == 1;
}

int main(int argc, const char * argv[]) {

    if (getRand() || Foo())
    {
        std::cout<<"Hello World \n";
    }

    return 0;
}

thanks in advance, Lin

Answer 1

Yes, it is a guaranteed feature called short circuit evaluation.

Likewise, an expression false && expression will never evaluate the right expression.