[Bug c/66773] sign-compare warning for == and != are pretty useless

["daniel.marjamaki at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66773

--- Comment #4 from Daniel Marjamäki <daniel.marjamaki at gmail dot com> ---
absolutely. there are often bugs in the boundaries.

well. I was hoping to get more optimistic response.

how about this.. imagine that we wrote a "possible division by zero" warning
for every integer division that uses a non-constant rhs. every warning where
rhs can't really be zero would be a false positive. That would be very noisy
imo.

imho the false positive rate should be similar here. If there is a comparison
'a == -1' and a is unsigned then this warning is useless if a can't be
0xffffffff. if a has arbitrary values then statistically it's as likely that a
is 0xffffffff and 0. So I guess the false positive rate is somewhat similar.

Maybe the message can be tweaked?

comparison between signed and unsigned integer expressions [-Wsign-compare]

I think this message is fine for relational comparisons. A sign-cast is a
reasonable solution.

For == and != I am afraid the message is somewhat misleading. A sign-cast is
not a good solution.
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From: "dmalcolm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug jit/66783] New: No error-checking for creating structs containing opaque structs
Date: Tue, 07 Jul 2015 00:37:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf783

            Bug ID: 66783
           Summary: No error-checking for creating structs containing
                    opaque structs
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: jit
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
            Blocks: 66627
  Target Milestone: ---

Problem reported on mailing list here:
  https://gcc.gnu.org/ml/jit/2015-q3/msg00022.html

We need to reject this kind of thing at the API boundary.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?idf627
[Bug 66627] Tracker bug for jit bugs affecting ravi