[Bug c/96126] New: conflicting attribute section accepted on redeclaration

[Bug c/96126] New: conflicting attribute section accepted on redeclaration

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96126

            Bug ID: 96126
           Summary: conflicting attribute section accepted on
                    redeclaration
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

GCC rejects conflicting attribute section on same declaration but fails to
detect the far more likely and difficult to debug problem where the conflict is
on two declaration of the same function or variable:

$ cat z.c && gcc -O2 -S -Wall z.c
__attribute__ ((section ("s1"), section ("s2")))  // error (good)
void f1 (void);

__attribute__ ((section ("s2"))) __attribute ((section ("s3")))
void f2 (void);                                   // error (good)

__attribute__ ((section ("s4"))) void f3 (void);
__attribute__ ((section ("s5"))) void f3 (void);  // missing diagnosic

z.c:2:6: error: section of ‘f1’ conflicts with previous declaration
    2 | void f1 (void);
      |      ^~
z.c:5:6: error: section of ‘f2’ conflicts with previous declaration
    5 | void f2 (void);                                   // error (good)
      |      ^~

In addition, referring to a previous declaration in the first declaration of a
symbol is misleading.

Clang diagnoses all instances of the problem as expected (although it too
suffers from the "previous declaration" problem):

z.c:1:33: warning: section does not match previous declaration [-Wsection]
__attribute__ ((section ("s1"), section ("s2")))  // error (good)
                                ^
z.c:1:17: note: previous attribute is here
__attribute__ ((section ("s1"), section ("s2")))  // error (good)
                ^
z.c:4:48: warning: section does not match previous declaration [-Wsection]
__attribute__ ((section ("s2"))) __attribute ((section ("s3")))
                                               ^
z.c:4:17: note: previous attribute is here
__attribute__ ((section ("s2"))) __attribute ((section ("s3")))
                ^
z.c:8:17: warning: section does not match previous declaration [-Wsection]
__attribute__ ((section ("s5"))) void f3 (void);  // missing diagnosic
                ^
z.c:7:17: note: previous attribute is here
__attribute__ ((section ("s4"))) void f3 (void);
                ^
3 warnings generated.

[Bug c/96126] conflicting attribute section accepted on redeclaration

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96126

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org
   Last reconfirmed|                            |2020-07-08
           Keywords|                            |diagnostic
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
I'm testing a fix.

[Bug c/96126] conflicting attribute section accepted on redeclaration

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96126

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=78666

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
See also pr78666.

Patch: https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549686.html

[Bug c/96126] conflicting attribute section accepted on redeclaration

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96126

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Sebor <msebor@gcc.gnu.org>:

https://gcc.gnu.org/g:71ad0b5dde449ee1f6b755a99f5c52152e375835

commit r11-3239-g71ad0b5dde449ee1f6b755a99f5c52152e375835
Author: Martin Sebor <msebor@redhat.com>
Date:   Wed Sep 16 14:04:01 2020 -0600

    Detect conflicts between incompatible uses of the same attribute (PR
c/78666).

    Resolves:
    PR c/78666 - conflicting attribute alloc_size accepted
    PR c/96126 - conflicting attribute section accepted on redeclaration

    gcc/c-family/ChangeLog:

            PR c/78666
            PR c/96126
            * c-attribs.c (validate_attr_args): New function.
            (validate_attr_arg): Same.
            (handle_section_attribute): Call it.  Introduce a local variable.
            (handle_alloc_size_attribute):  Same.
            (handle_alloc_align_attribute): Same.

    gcc/testsuite/ChangeLog:

            PR c/78666
            PR c/96126
            * gcc.dg/attr-alloc_align-5.c: New test.
            * gcc.dg/attr-alloc_size-13.c: New test.
            * gcc.dg/attr-section.c: New test.
            * c-c++-common/builtin-has-attribute-3.c: Add xfails due to
expected
            warnings to be cleaned up.

[Bug c/96126] conflicting attribute section accepted on redeclaration

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96126

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.0
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Patch committed in r11-3239.