Re: Fix bogus warning with -Wlogical-not-parentheses (PR c/77292)

[Martin Sebor]

+foo (int a, int b)
+{
+  int r = 0;
+  r += !a == (a < b);
+  r += !a == (a > b);
+  r += !a == (a >= b);
+  r += !a == (a <= b);
+  r += !a == (a != b);
+  r += !a == (a == b);
+  r += !a == (a || b);
+  r += !a == (a && b);
+  r += !a == (!b);
+
+  r += !a == (a ^ b); /* { dg-warning "logical not is only applied to the left hand 
side of comparison" } */
+  r += !a == (a | b); /* { dg-warning "logical not is only applied to the left hand 
side of comparison" } */
+  r += !a == (a & b); /* { dg-warning "logical not is only applied to the left hand 
side of comparison" } */

A question more than a comment: warning on the last three expressions
above makes sense to me when the operands are integers but I'm less
sure that the same logic applies when the operands are Boolean.  Does
it make sense to issue the warning for those given that (a | b) and
(a & b) are the same as (a || b) and (a && b) for which the warning
is suppressed?

In other words, is warning on the latter of the two below but not on
the former a good idea or should they be treated the same way?

$ cat t.c && gcc -S -Wlogical-not-parentheses t.c
_Bool f (int a, _Bool b, _Bool c)
{
  _Bool r;

  r = !a == (b || c);
  r = !a == (b | c);

  return r;
}
t.c: In function ‘f’:
t.c:6:10: warning: logical not is only applied to the left hand side of 
comparison [-Wlogical-not-parentheses]
   r = !a == (b | c);
          ^~
t.c:6:7: note: add parentheses around left hand side expression to 
silence this warning
   r = !a == (b | c);
       ^~
       ( )

Also, having hardly any experience with the fixit hints, I'm not
sure how helpful this one is.  It seems really hard to tell what
it suggests as the fix (I had to try it both ways to see).  I
think would be a lot clearer if it showed the full expression
rather than just the operators.  Would printing this instead be
doable?

   r = !a == (b | c);
       ^~
       (!a)

Martin