[Bug c++/54955] New: alignas example in gcc 4.8 changes.html won't compile

[Bug c++/54955] New: alignas example in gcc 4.8 changes.html won't compile

[mib.bugzilla at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

             Bug #: 54955
           Summary: alignas example in gcc 4.8 changes.html won't compile
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mib.bugzilla@gmail.com


gcc 4.8 changes.html file gives this example:
alignas(double) int i;

But the snapshot from Oct 14 2012 gives this message:
g++ -c -std=c++11 alignas.cpp
alignas.cpp:1:1: error: expected unqualified-id before 'alignas'
 alignas(double) int f;
 ^

If alignas is moved to the end of the declaration it compiles okay:
int f alignas(double);

doc error?

Could you also confirm whether c++11 keyword alignas is the same as c1x
_Alignas?

Thanks and regards

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[mib.bugzilla at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

--- Comment #1 from mib.bugzilla at gmail dot com 2012-10-17 16:21:56 UTC ---
p.s.
This example is given here: http://en.cppreference.com/w/cpp/language/alignas

char alignas(128) cacheline[128];

but g++ complains similarly to the root report

[Bug web/54955] alignas example in gcc 4.8 changes.html won't compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-17 17:21:58 UTC ---
I *think* the example is valid, so it's a compiler bug ... but I'm not sure.

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler at
                   |                            |googlemail dot com

--- Comment #3 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-10-17 19:55:34 UTC ---
I agree that this should be accepted (The grammar of a /simple-declaration/ in
Clause 7 says so).

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-10-17
     Ever Confirmed|0                           |1

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

Dodji Seketeli <dodji at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|dodji at gcc dot gnu.org    |

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-10-26 13:31:33 UTC ---
Thanks Dodji!

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[dodji at seketeli dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

--- Comment #5 from dodji at seketeli dot org <dodji at seketeli dot org> 2012-10-26 17:42:44 UTC ---
> --- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-10-26 13:31:33 UTC ---
>
> Thanks Dodji!

You are welcome.  :)

A candidate patch was proposed at
http://gcc.gnu.org/ml/gcc-patches/2012-10/msg02439.html

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

--- Comment #6 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-10-31 08:55:51 UTC ---
Author: dodji
Date: Wed Oct 31 08:55:43 2012
New Revision: 193029

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=193029
Log:
PR c++/54955 - Fail to parse alignas expr at the beginning of a declaration

In this PR, g++ embarrassingly fails to parse the simple alignas
expression below:

    alignas(double) int f;

even though the simple-declaration production in Clause 7 suggests
otherwise.

Fixed thus and tested on x86_64-unknown-linux-gnu against trunk.

gcc/cp

    PR c++/54955
    * parser.c (cp_nth_tokens_can_be_std_attribute_p): Recognize the
    'Alignas' keyword as the beginning of a c++11 attribute specifier.
    Update the comment of the function.
    (cp_next_tokens_can_be_gnu_attribute_p): Update the comment of the
    function.

gcc/testsuite/

    PR c++/54955
    * g++.dg/cpp0x/gen-attrs-48-2.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/gen-attrs-48-2.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/parser.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/54955] alignas example in gcc 4.8 changes.html won't compile

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54955

Dodji Seketeli <dodji at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #7 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-10-31 09:01:49 UTC ---
This should be fixed in trunk (4.8)