zagadka - postinkrementacja

http://www.open-std.org/jtc1​/sc22/wg21/docs​/cwg_defects.html#637

It should be noted that a similar expression     i = i++ + 1; is still not well-defined, since the incrementation side-effect remains unsequenced with respect to the assignment side-effect. [..] i = i++ + 1;        // the behavior is undefined

Taki zapis miał niezdefiniowane zachowanie, ale najwyraźniej już nie ma.

//edit:
http://en.cppreference.com/w​/cpp/language/eval_order

20) In every simple assignment expression E1=E2 and every compound assignment expression E1@=E2, every value computation and side-effect of E2 is sequenced before every value computation and side effect of E1 (since C++17)

Przed C++17 ten zapis miał niezdefiniowane zachowanie, od 17 jest poprawny.