[Bug c/52181] New: [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[Bug c/52181] New: [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

             Bug #: 52181
           Summary: [4.7 Regression] merge_decls doesn't handle
                    DECL_USER_ALIGN properly
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: jakub@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org


extern const int v1[];
const int __attribute__((aligned(16))) v1[] = { 0 };
extern const int __attribute__((aligned(16))) v2[];
const int v2[] = { 0 };
extern const int __attribute__((aligned(16))) v3[];
const int __attribute__((aligned(16))) v3[] = { 0 };
const int __attribute__((aligned(16))) v4[] = { 0 };
int test[(__alignof__ (v4) != __alignof__ (v1)/* { dg-bogus "is negative" } */
 || __alignof__ (v4) != __alignof__ (v2)
 || __alignof__ (v4) != __alignof__ (v3)) ? -1 : 0];

fails with gcc 4.7, worked with 4.6, but it looks like the actual bug is of an
earlier date, when DECL_USER_ALIGN bit has been moved from tree_decl_common
etc.
down into tree_base.

[Bug c/52181] [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2012-02-09
      Known to work|                            |4.6.3
   Target Milestone|---                         |4.7.0
     Ever Confirmed|0                           |1
      Known to fail|                            |4.7.0

[Bug c/52181] [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-02-09 09:07:20 UTC ---
Created attachment 26621
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26621
gcc47-pr52181.patch

Untested fix.  The testcase shows that the C++ FE has a similar bug, but in the
other direction, when olddecl has aligned attribute and newdecl doesn't.

[Bug c/52181] [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[uweigand at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

Ulrich Weigand <uweigand at gcc dot gnu.org> changed:

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

--- Comment #2 from Ulrich Weigand <uweigand at gcc dot gnu.org> 2012-02-09 18:33:12 UTC ---
The regression is present on tip of 4.6 branch as well, exposed by recent
backports from mainline.

[Bug c/52181] [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-02-14 06:15:42 UTC ---
Author: jakub
Date: Tue Feb 14 06:15:35 2012
New Revision: 184193

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=184193
Log:
    PR c/52181
    * c-decl.c (merge_decls): Copy DECL_USER_ALIGN bit from olddecl to
    newdecl.

    * decl.c (duplicate_decls): If olddecl has bigger DECL_ALIGN than
    newdecl, copy DECL_ALIGN to newdecl and or DECL_USER_ALIGN bits.

    * c-c++-common/pr52181.c: New test.

Added:
    trunk/gcc/testsuite/c-c++-common/pr52181.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c-decl.c
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/decl.c
    trunk/gcc/testsuite/ChangeLog

[Bug c/52181] [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-02-14 09:47:59 UTC ---
Fixed.

[Bug c/52181] [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[uweigand at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

--- Comment #5 from Ulrich Weigand <uweigand at gcc dot gnu.org> 2012-02-14 17:22:23 UTC ---
Thanks for the quick fix!  Are you planning to backport to 4.6 as well?

[Bug c/52181] [4.7 Regression] merge_decls doesn't handle DECL_USER_ALIGN properly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52181

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-02-14 23:34:40 UTC ---
Author: jakub
Date: Tue Feb 14 23:34:34 2012
New Revision: 184242

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=184242
Log:
    Backported from mainline
    2012-02-14  Jakub Jelinek  <jakub@redhat.com>

    PR c/52181
    * c-decl.c (merge_decls): Copy DECL_USER_ALIGN bit from olddecl to
    newdecl.

    * decl.c (duplicate_decls): If olddecl has bigger DECL_ALIGN than
    newdecl, copy DECL_ALIGN to newdecl and or DECL_USER_ALIGN bits.

    * c-c++-common/pr52181.c: New test.

Added:
    branches/gcc-4_6-branch/gcc/testsuite/c-c++-common/pr52181.c
Modified:
    branches/gcc-4_6-branch/gcc/ChangeLog
    branches/gcc-4_6-branch/gcc/c-decl.c
    branches/gcc-4_6-branch/gcc/cp/ChangeLog
    branches/gcc-4_6-branch/gcc/cp/decl.c
    branches/gcc-4_6-branch/gcc/testsuite/ChangeLog