Shift operands sequenced in C++17

Question

I read in the C++17 Standard $8.5.7.4:

The expression E1 is sequenced before the expression E2.

for shift operators.

Als

Answer 1

Standard is clear about the order of evaluation of the operands of the shift operator.

n4659 - §8.8 (p4):

The expression E1 is sequenced before the expression E2.

There is no undefined behavior in the expression i++ << i, it is well defined. It is a bug in Clang and GCC both.