[Bug libstdc++/56019] New: max_align_t should be in std namespace

[Bug libstdc++/56019] New: max_align_t should be in std namespace

[kretz at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019

             Bug #: 56019
           Summary: max_align_t should be in std namespace
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: kretz@kde.org


According to 3.11.2 in the C++11 standard max_align_t should be inside the std
namespace (i.e. the text talks about use of alignof(std::max_align_t)). GCC
only provides ::max_align_t, though:

% cat main.cpp                                                                 
                                                                               
                                                                #include
<cstddef>
int main()
{
    return alignof(std::max_align_t);
}

% /opt/gcc-4.7.2/bin/g++ -Wall -std=c++11 -o test main.cpp
main.cpp: In function ‘int main()’:
main.cpp:4:20: error: ‘max_align_t’ is not a member of ‘std’
main.cpp:4:20: note: suggested alternative:
In file included from
/home/.opt/gcc-4.7.2/bin/../lib/gcc/x86_64-suse-linux-gnu/4.7.2/../../../../include/c++/4.7.2/cstddef:44:0,
                 from main.cpp:1:
/home/.opt/gcc-4.7.2/bin/../lib/gcc/x86_64-suse-linux-gnu/4.7.2/include/stddef.h:426:3:
note:   ‘max_align_t’

% /opt/gcc-4.8-snapshot/bin/g++ -Wall -std=c++11 -o test main.cpp
main.cpp: In function ‘int main()’:
main.cpp:4:20: error: ‘max_align_t’ is not a member of ‘std’
     return alignof(std::max_align_t);
                    ^
main.cpp:4:20: note: suggested alternative:
In file included from
/home/.opt/gcc-4.8-snapshot/include/c++/4.8.0/cstddef:44:0,
                 from main.cpp:1:
/home/.opt/gcc-4.8-snapshot/lib/gcc/x86_64-suse-linux-gnu/4.8.0/include/stddef.h:425:3:
note:   ‘max_align_t’
 } max_align_t;
   ^

[Bug libstdc++/56019] max_align_t should be in std namespace

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-01-17
     Ever Confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2013-01-17 14:52:45 UTC ---
<cstddef> just hasn't been updated since max_align_t was added to <stddef.h>

[Bug libstdc++/56019] max_align_t should be in std namespace

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |paolo.carlini at oracle dot com

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Mine.

[Bug libstdc++/56019] max_align_t should be in std namespace

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.9.0

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed for 4.9.0. If somebody is interested in 4.8.x too, backporting the patch
should not be a big deal.

[Bug libstdc++/56019] max_align_t should be in std namespace

[Jobst.Ziebell at mailbox dot tu-dresden.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019

Jobst.Ziebell at mailbox dot tu-dresden.de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |Jobst.Ziebell at mailbox dot tu-dr
                   |                            |esden.de

--- Comment #4 from Jobst.Ziebell at mailbox dot tu-dresden.de ---
The fix introduces another problem. Whenever '__need_size_t' is defined prior
to the inclusion of <cstddef>, the type 'max_align_t' will not have been
defined.
This inevitably causes a compiler error:

#define __need_size_t
#include <cstddef>

int main( void )
{
    return 0;
}

This happens on Mac OS X 10.9. In my case it got triggered by including
<gmp.h>.
Presumably this bug also occurs when #defining the other '__need_*' macros.

[Bug libstdc++/56019] max_align_t should be in std namespace

[Jobst.Ziebell at mailbox dot tu-dresden.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019

--- Comment #5 from Jobst.Ziebell at mailbox dot tu-dresden.de ---
I would propose adding something like

#ifdef _GCC_MAX_ALIGN_T
...
#endif
around the 'using' declaration.

(Though I really have no idea whatsoever off gcc internals...)

[Bug libstdc++/56019] max_align_t should be in std namespace

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56019

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jobst.Ziebell from comment #4)
> Presumably this bug also occurs when #defining the other '__need_*' macros.

Which user code should never be doing anyway.

GMP is broken (and already fixed upstream).

This is documented at http://gcc.gnu.org/gcc-4.9/porting_to.html and isn't
going to be changed to accomodate broken libraries.