[Bug c++/78929] New: Incorrect implementation of Refining Expression Evaluation Order for Idiomatic C++

[boostcpp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78929

            Bug ID: 78929
           Summary: Incorrect implementation of Refining Expression
                    Evaluation Order for Idiomatic C++
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: boostcpp at gmail dot com
  Target Milestone: ---

GCC 7 claims to support Refining Expression Evaluation Order for Idiomatic C++,
proposed by P0145R3.
https://gcc.gnu.org/projects/cxx-status.html#cxx1z

Current GCC 7 head does incorrect evaluation on this code.

#include <iostream>

int main()
{
    int i = 0 ;
    std::cout << ++i + ++i ;
}

The output should be 3 but current GCC 7 head output 4.