[Bug c++/116151] New: [7.1 Regression] G++ fails to diagnose -Waggressive-loop-optimizations when going past the end of an array

[arsen at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116151

            Bug ID: 116151
           Summary: [7.1 Regression] G++ fails to diagnose
                    -Waggressive-loop-optimizations when going past the
                    end of an array
           Product: gcc
           Version: 7.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arsen at gcc dot gnu.org
  Target Milestone: ---

The following code, in C++ mode since GCC 7.1 (works on 6.5), at -O3 creates an
infinite loop and fails to produce a diagnostic:

  void
  f ()
  {
      int arr[48];
      extern int g (int);
      for (int i = 0; i < 55; i++)
          arr[i] = g (arr[i]);
  }

... however, in C, the above produces a correct diagnostic (and a non-infinite
loop).

(reduced from https://bugs.gentoo.org/936237 )