[Bug c/61053] New: _Alignas(long long) reduces alignment of long long

[Bug c/61053] New: _Alignas(long long) reduces alignment of long long

[pdziepak at quarnos dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

            Bug ID: 61053
           Summary: _Alignas(long long) reduces alignment of long long
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pdziepak at quarnos dot org

On 32 bit x86 definition like the following one:

_Alignas(long long) long long ll;

causes GCC 4.9 to produce error:

‘_Alignas’ specifiers cannot reduce alignment of ‘ll’

Only types long long and double seem to be affected. The problem is not present
on GCC 4.8.2.
>From gcc-bugs-return-450500-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Sun May 04 12:07:15 2014
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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long
Date: Sun, 04 May 2014 12:07:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?ida053

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-05-04
      Known to work|                            |4.8.2
            Summary|_Alignas(long long) reduces |[4.9/4.10 Regression]
                   |alignment of long long      |_Alignas(long long) reduces
                   |                            |alignment of long long
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
FWIW, it also compiles OK as C++11 with s/_Alignas/alignas/

[Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |i?86-*-*
           Priority|P3                          |P2
   Target Milestone|---                         |4.9.1

[Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |mpolacek at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I think I have a patch.

[Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Thu May  8 18:19:09 2014
New Revision: 210230

URL: http://gcc.gnu.org/viewcvs?rev=210230&root=gcc&view=rev
Log:
    PR c/61053
c-family/
    * c-common.c (min_align_of_type): New function factored out from...
    (c_sizeof_or_alignof_type): ...here.
    * c-common.h (min_align_of_type): Declare.
c/
    * c-decl.c (grokdeclarator): Use min_align_of_type instead of
    TYPE_ALIGN_UNIT.
testsuite/
    * gcc.dg/pr61053.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/pr61053.c
Modified:
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c-common.c
    trunk/gcc/c-family/c-common.h
    trunk/gcc/c/ChangeLog
    trunk/gcc/c/c-decl.c
    trunk/gcc/testsuite/ChangeLog

[Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.

[Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I'm about to backport the fix even into 4.9 branch, thanks.

[Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Wed Jun  4 08:22:22 2014
New Revision: 211214

URL: http://gcc.gnu.org/viewcvs?rev=211214&root=gcc&view=rev
Log:
    PR c/61053
c-family/
    * c-common.c (min_align_of_type): New function factored out from...
    (c_sizeof_or_alignof_type): ...here.
    * c-common.h (min_align_of_type): Declare.
c/
    * c-decl.c (grokdeclarator): Use min_align_of_type instead of
    TYPE_ALIGN_UNIT.
testsuite/
    * gcc.dg/pr61053.c: New test.

Added:
    branches/gcc-4_9-branch/gcc/testsuite/gcc.dg/pr61053.c
Modified:
    branches/gcc-4_9-branch/gcc/c-family/ChangeLog
    branches/gcc-4_9-branch/gcc/c-family/c-common.c
    branches/gcc-4_9-branch/gcc/c-family/c-common.h
    branches/gcc-4_9-branch/gcc/c/ChangeLog
    branches/gcc-4_9-branch/gcc/c/c-decl.c
    branches/gcc-4_9-branch/gcc/testsuite/ChangeLog

[Bug c/61053] [4.9/4.10 Regression] _Alignas(long long) reduces alignment of long long

[fxcoudert at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61053

Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |fxcoudert at gcc dot gnu.org,
                   |                            |iains at gcc dot gnu.org,
                   |                            |mikestump at comcast dot net
         Resolution|FIXED                       |---

--- Comment #8 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> ---
The testcase introduced in fixing this bug (gcc.dg/pr61053.c) fails on
x86_64-apple-darwin14 with -m32, because of excess errors:

gcc.dg/pr61053.c:70:28: error: '_Alignas' specifiers cannot reduce alignment of
'ldi'
gcc.dg/pr61053.c:71:33: error: '_Alignas' specifiers cannot reduce alignment of
'ldl'
gcc.dg/pr61053.c:72:38: error: '_Alignas' specifiers cannot reduce alignment of
'ldll'
gcc.dg/pr61053.c:73:30: error: '_Alignas' specifiers cannot reduce alignment of
'ldf'
gcc.dg/pr61053.c:74:31: error: '_Alignas' specifiers cannot reduce alignment of
'ldd'

The testcase does not expect those for ia32, but we have them on darwin because
long double has 16 bytes alignment both at -m32 and -m64.
I don't know what's the best way to adapt the dg-error clauses, however.