[Bug libstdc++/56627] New: class hash instead of struct hash

[Bug libstdc++/56627] New: class hash instead of struct hash

[andreas.hansson at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

             Bug #: 56627
           Summary: class hash instead of struct hash
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: andreas.hansson@gmail.com


In the gcc 4.8.0 c++ standard library headers, bitset and bits/stl_bvector.h
both incorrectly use class instead of struct for the hash function.

For example, bits/stl_bvector.h:

#if __cplusplus >= 201103L
   template<typename> friend class hash;
#endif

class should be struct

[Bug libstdc++/56627] class hash instead of struct hash

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2013-03-15 19:18:23 UTC ---
In C++, class and struct are interchangeable.

[Bug libstdc++/56627] class hash instead of struct hash

[andreas.hansson at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #2 from ahansson <andreas.hansson at gmail dot com> 2013-03-15 21:04:01 UTC ---
(In reply to comment #1)
> In C++, class and struct are interchangeable.

Agreed. Technically the code is ok, and in line with the language standard. 

However, as at least one of the most popular compilers (clang 3.2 RELEASE with
-Wall) issues a warning for this. Thus, it might be worthwhile fixing.

[Bug libstdc++/56627] class hash instead of struct hash

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> 2013-03-15 21:17:15 UTC ---
(In reply to comment #2)
> (In reply to comment #1)rd. 
> However, as at least one of the most popular compilers (clang 3.2 RELEASE with
> -Wall) issues a warning for this. Thus, it might be worthwhile fixing.

And it only issues it because it tries to be compatible with MS's compiler.
  I think this is broken to issue a warning at all and rather see clang fixed
and/or ignored in this case.

[Bug libstdc++/56627] class hash instead of struct hash

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2013-03-16 02:22:39 UTC ---
I'm happy to fix things in libstdc++ that are broken and cause real problems
for clang users, but this is correct C++ and causes a spurious warning. Not a
bug, not worth wasting time on.

[Bug libstdc++/56627] class hash instead of struct hash

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-03-16 09:40:02 UTC ---
I agree. And we discussed it already somewhere.

[Bug libstdc++/56627] class hash instead of struct hash

[andreas.hansson at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #6 from ahansson <andreas.hansson at gmail dot com> 2013-03-16 12:01:39 UTC ---
(In reply to comment #4)
> I'm happy to fix things in libstdc++ that are broken and cause real problems
> for clang users, but this is correct C++ and causes a spurious warning. Not a
> bug, not worth wasting time on.

The potential for "real problems" was my main reason for pointing it out. I ran
some (unrelated) tests on Fedora Rawhide (fc19) with clang 3.2 RELEASE and gcc
4.8.0 and this issue popped up as -Wall -Werror was used for the project in
question.

The two lines mentioned are the only issues encountered. If it is worth
"fixing" or not I leave up to you to decide, I merely wanted to highlight the
potential issues.

[Bug libstdc++/56627] class hash instead of struct hash

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |d.frey at gmx dot de

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> ---
*** Bug 57730 has been marked as a duplicate of this bug. ***

[Bug libstdc++/56627] class hash instead of struct hash

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |whatmannerofburgeristhis@gm
                   |                            |ail.com

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 58025 has been marked as a duplicate of this bug. ***

[Bug libstdc++/56627] class hash instead of struct hash

[whatmannerofburgeristhis at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #9 from Matt Arsenault <whatmannerofburgeristhis at gmail dot com> ---
(In reply to Andrew Pinski from comment #8)
> *** Bug 58025 has been marked as a duplicate of this bug. ***

They don't have to be consistent by the standard, but the purpose of warnings
is not to strictly report deviations from the standard. Many point out likely
mistakes or inconsistencies in "standard" conforming code (e.g. -Wlogical-op).
This is an absolutely trivial fix.

[Bug libstdc++/56627] class hash instead of struct hash

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Matt Arsenault from comment #9)
> (In reply to Andrew Pinski from comment #8)
> > *** Bug 58025 has been marked as a duplicate of this bug. ***
> 
> They don't have to be consistent by the standard, but the purpose of
> warnings is not to strictly report deviations from the standard. Many point
> out likely mistakes or inconsistencies in "standard" conforming code (e.g.
> -Wlogical-op). This is an absolutely trivial fix.

Actually this warning makes less sense than -Wlogical-op due to the way struct
and class are defined.  -Wlogical-op makes sense since due to forgetting how ||
and && interact, there is no interaction here, only using struct in one case
and class in another which is valid and known what happens even without looking
up what happens.  The real reason why they added this option is due to another
compiler which implements non-standard behavior for struct and class (not
naming the company here but they also don't care about C99).

[Bug libstdc++/56627] class hash instead of struct hash

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm think I'm just going to change the code to shut everyone up, despite it
being a nonsense warning about a non-issue, because I'm sick of these
discussions.

Fine, you win, we'll silence the stupid warning.

[Bug libstdc++/56627] class hash instead of struct hash

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bluescarni at gmail dot com

--- Comment #12 from Jonathan Wakely <redi at gcc dot gnu.org> ---
*** Bug 58030 has been marked as a duplicate of this bug. ***

[Bug libstdc++/56627] class hash instead of struct hash

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #13 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Jon, I have two spare minutes and if you don't mind I'm taking care of the
stupid change myself.

[Bug libstdc++/56627] class hash instead of struct hash

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #14 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Sure, I was going to do it this evening but please go ahead, thanks.

[Bug libstdc++/56627] class hash instead of struct hash

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56627

--- Comment #15 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Done for 4.8.2 and 4.9.0.