[Bug c/43772] Errant -Wlogical-op warning when testing limits

["marc.glisse at normalesup dot org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43772

--- Comment #19 from Marc Glisse <marc.glisse at normalesup dot org> 2012-04-28 22:16:55 UTC ---
(In reply to comment #18)
> I'm afraid that false positives would still be likely.
> For example, suppose we're on a platform where
> INT_MAX = LONG_MAX < INTMAX_MAX.  Then:
> 
>   intmax_t i = (whatever);
>   if (INT_MAX < i && i <= LONG_MAX)
>      print ("i is in 'long' but not 'int' range");

Have you actually seen that? I would imagine the following to be more common:
if(i<=INT_MAX)
  print("i is in 'int'");
else if(i<=LONG_MAX)
  ...

> This sort of thing is fairly common in portable code,
> and GCC shouldn't warn about it merely because
> we're on a platform where the two tests cannot both
> be true when INT_MAX == LONG_MAX.

Well, can you define a set of circumstances where gcc could / should warn?
a<i&&i<=a seems to be quite precisely what this warning is about. Or maybe
a==INT_MAX (adapt depending on the type) should disable the warning, as a
special case?

Please also remember that we are not talking of having this warning by default,
this is an isolated warning not even included in -Wall -Wextra.