C++ catching dangling reference

Question

Suppose the following piece of code

struct S {
    S(int & value): value_(value) {}
    int & value_;
};

S function() {
    int value = 0;
    retur         


        

Answer 1

This is perfectly valid code.

If you call your function and bind the temporary to a const reference the scope gets prolonged.

const S& s1 = function(); // valid

S& s2 = function(); // invalid

This is explicitly allowed in the C++ standard.

See 12.2.4:

There are two contexts in which temporaries are destroyed at a different point than the end of the full-expression.

and 12.2.5:

The second context is when a reference is bound to a temporary. The temporary to which the reference is bound or the temporary that is the complete object of a subobject to which the reference is bound persists for the lifetime of the reference except: [...]