Does an assignment operator in c++ return rvalue or lvalue?

Question

Does an assignment operator in c++ returns an rvalue or an lvalue? And if it is an lvalue, which of the two arguments will be incremented here?

(a = b)++

Syphilology

Have you tried it? A simple debug message should tell you the answer. – Ania

It works, and it returns lvalue for first argument, but maybe it's undefined or unspecified behavior? Or maybe works only for this case? – Brezhnev

Answer 1

It returns a lvalue. Per § 5.17:

The assignment operator (=) and the compound assignment operators all group right-to-left. All require a modifiable lvalue as their left operand and return an lvalue referring to the left operand.

If those objects have an user-defined operator for assignment, then it depends on implementation and declaration (return type) of the operator=.

So normally, after

(a = b)++

The object a will be incremented.

Cordwood