[Bug c/77292] New: Spurious "warning: logical not is only applied to the left hand side of comparison"

[terra at gnome dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77292

            Bug ID: 77292
           Summary: Spurious "warning: logical not is only applied to the
                    left hand side of comparison"
           Product: gcc
           Version: 5.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: terra at gnome dot org
  Target Milestone: ---

The warning introduced in bug 62183 is trigger-happy.

int
foo (int a, int b)
{
  // Make it obvious that these are booleans.
  a = !!a;
  b = !!b;

  return !a == b;
}


# gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.2) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

# gcc -c -Wall -O2 bbb.c 
bbb.c: In function ‘foo’:
bbb.c:8:13: warning: logical not is only applied to the left hand side of
comparison [-Wlogical-not-parentheses]
   return !a == b;
             ^
This is silly and out-right illogical when "a" and "b" are booleans.
"!a == b" means the same as "!(a == b)", so the warning is pointing out
that I might have meant something else that, upon inspection, is seen
to be the same thing.

Note: by "boolean" I mean an integer with value 0 or 1.