Constructor called on return statement

Question

Consider the following example:

class X {
public:
    X() = default;
    X(const X&) = default;
    X(X&&) = delete;
};

X foo() {
    X result;
             


        

Answer 1

result is not an lvalue after returning from foo(), but a prvalue, so it is allowed to call the move constructor.

From CppReference:

The following expressions are prvalue expressions:

• a function call or an overloaded operator expression, whose return type is non-reference, such as str.substr(1, 2), str1 + str2, or it++

It is possible that Clang detected that the return value is unused and threw it away directly, while GCC didn't.