returning references to local variable [duplicate]

Answer 1

In no case (not intVal, not intRef, and not intPtr) does i necessarily stick around after foo returns.

The value on the stack which was previously occupied by i may or may not be changed at any time, after foo returns.

For example (on some CPUs and O/Ses), it is likely to be changed by any subsequent call to a subroutine, and may be changed if a hardware interrupt occurs.

Answer 2

Nope, none of those will extend the lifetime of the local variable. Nothing in C++ will have that effect. Local objects in C++ live until the end of the scope in which they are declared, end of story.

The only rule which, at first glance, seems to follow different rules is this:

int foo() {
    return 42;
}

int main() {
    const int& i = foo();
    // here, `i` is a reference to the temporary that was returned from `foo`, and whose lifetime has been extended
}

That is, a const reference can extend the lifetime of a temporary being assigned to it.

But that requires the function to return a value, not a reference, and the callee to bind the return value to a const reference, neither of which are done in your code.