[Bug tree-optimization/98512] New: “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[Bug tree-optimization/98512] New: “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

            Bug ID: 98512
           Summary: “#pragma GCC diagnostic ignored” ineffective in
                    conjunction with alias attribute
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fw at gcc dot gnu.org
                CC: msebor at gcc dot gnu.org
  Target Milestone: ---

The following test case has been extracted from a glibc build failure on
powerpc64le, but it appears to be target-independent.

This produces a -WWstringop-overread warning at -O2, even though the warning
has been suppressed.

void *
__rawmemchr_ppc (const void *s, int c)
{
#pragma GCC diagnostics push
#pragma GCC diagnostic ignored "-Wstringop-overflow="
#pragma GCC diagnostic ignored "-Wstringop-overread"
  if (c != 0)
    return __builtin_memchr (s, c, (unsigned long)-1);
#pragma GCC diagnostics pop
  return (char *)s + __builtin_strlen (s);
}
extern __typeof (__rawmemchr_ppc) __EI___rawmemchr_ppc
  __attribute__((alias ("__rawmemchr_ppc")));

t.c:8:12: warning: ‘__builtin_memchr’ specified bound 18446744073709551615
exceeds maximum object size 9223372036854775807 [-Wstringop-overread]           
    8 |     return __builtin_memchr (s, c, (unsigned long)-1);                 
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Seen with: 11.0.0 20210104 (experimental)

[Bug tree-optimization/98512] [11 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |11.0
             Status|UNCONFIRMED                 |NEW
            Summary|“#pragma GCC diagnostic     |[11 Regression] “#pragma
                   |ignored” ineffective in     |GCC diagnostic ignored”
                   |conjunction with alias      |ineffective in conjunction
                   |attribute                   |with alias attribute
   Last reconfirmed|                            |2021-01-05
     Ever confirmed|0                           |1
      Known to work|                            |10.2.0

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning looks for the location into which the memchr caller was inlined (to
see if the caller is defined in a system header but itself called from user
code).  Without the alias it doesn't find one (because the caller isn't called
from anywhere) but with the alias it finds the memchr caller, __rawmemchr_ppc.

[Bug tree-optimization/98512] [11 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

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
             Status|NEW                         |ASSIGNED

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Let me see what can be done about it.

[Bug tree-optimization/98512] [11 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.0

[Bug tree-optimization/98512] [11 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=98664,
                   |                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=98465

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
My patches for pr98664 and pr98465 seem to also fix this.

[Bug tree-optimization/98512] [11 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Patch: https://gcc.gnu.org/pipermail/gcc-patches/2021-January/563862.html

A workaround until the patch is approved, is to move the warning suppression
pragmas above the the function declaration.

[Bug tree-optimization/98512] [11 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

--- Comment #5 from Florian Weimer <fw at gcc dot gnu.org> ---
Note, patch has been superseded:
https://gcc.gnu.org/pipermail/gcc-patches/2021-January/564060.html

[Bug tree-optimization/98512] [11 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.0                        |12.0

--- Comment #6 from Martin Sebor <msebor at gcc dot gnu.org> ---
The fix has been deferred to GCC 12:
https://gcc.gnu.org/pipermail/gcc-patches/2021-February/565551.html

[Bug tree-optimization/98512] [11/12 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

Martin Liška <marxin at gcc dot gnu.org> changed:

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

--- Comment #7 from Martin Liška <marxin at gcc dot gnu.org> ---
I noticed that for GCC 11.1 release.
@Florian: Is there any glibc workaround for it?

[Bug tree-optimization/98512] [11/12 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

--- Comment #8 from Florian Weimer <fw at gcc dot gnu.org> ---
This glibc commit works around the GCC issue:

commit 044e603b698093cf48f6e6229e0b66acf05227e4
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Feb 19 13:29:00 2021 +0100

    string: Work around GCC PR 98512 in rawmemchr

[Bug tree-optimization/98512] [11/12 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

--- Comment #9 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Florian Weimer from comment #8)
> This glibc commit works around the GCC issue:
> 
> commit 044e603b698093cf48f6e6229e0b66acf05227e4
> Author: Florian Weimer <fweimer@redhat.com>
> Date:   Fri Feb 19 13:29:00 2021 +0100
> 
>     string: Work around GCC PR 98512 in rawmemchr

Thanks!

[Bug tree-optimization/98512] [11/12 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

--- Comment #10 from Martin Sebor <msebor at gcc dot gnu.org> ---
Latest patch: https://gcc.gnu.org/pipermail/gcc-patches/2021-June/572515.html

[Bug tree-optimization/98512] [11/12 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

--- Comment #11 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:6feb628a706e86eb3f303aff388c74bdb29e7381

commit r12-1992-g6feb628a706e86eb3f303aff388c74bdb29e7381
Author: Martin Sebor <msebor@redhat.com>
Date:   Fri Jul 2 16:16:31 2021 -0600

    Improve warning suppression for inlined functions [PR98512].

    Resolves:
    PR middle-end/98871 - Cannot silence -Wmaybe-uninitialized at declaration
site
    PR middle-end/98512 - #pragma GCC diagnostic ignored ineffective in
conjunction with alias attribute

    gcc/ChangeLog:

            PR middle-end/98871
            PR middle-end/98512
            * diagnostic.c (get_any_inlining_info): New.
            (update_effective_level_from_pragmas): Handle inlining context.
            (diagnostic_enabled): Same.
            (diagnostic_report_diagnostic): Same.
            * diagnostic.h (struct diagnostic_info): Add ctor.
            (struct diagnostic_context): Add new member.
            * tree-diagnostic.c (set_inlining_locations): New.
            (tree_diagnostics_defaults): Set new callback pointer.

[Bug tree-optimization/98512] [11/12 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

--- Comment #12 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:6d3bab5d5adb3e28ddb16c97b0831efdea23cf7d

commit r12-2087-g6d3bab5d5adb3e28ddb16c97b0831efdea23cf7d
Author: Martin Sebor <msebor@redhat.com>
Date:   Tue Jul 6 13:41:02 2021 -0600

    Improve warning suppression for inlined functions.

    Resolves:
    PR middle-end/98871 - Cannot silence -Wmaybe-uninitialized at declaration
site
    PR middle-end/98512 - #pragma GCC diagnostic ignored ineffective in
conjunction with alias attribute

    gcc/ChangeLog:

            * builtins.c (warn_string_no_nul): Remove %G.
            (maybe_warn_for_bound): Same.
            (warn_for_access): Same.
            (check_access): Same.
            (check_strncat_sizes): Same.
            (expand_builtin_strncat): Same.
            (expand_builtin_strncmp): Same.
            (expand_builtin): Same.
            (expand_builtin_object_size): Same.
            (warn_dealloc_offset): Same.
            (maybe_emit_free_warning): Same.
            * calls.c (maybe_warn_alloc_args_overflow): Same.
            (maybe_warn_nonstring_arg): Same.
            (maybe_warn_rdwr_sizes): Same.
            * expr.c (expand_expr_real_1): Remove %K.
            * gimple-fold.c (gimple_fold_builtin_strncpy): Remove %G.
            (gimple_fold_builtin_strncat): Same.
            * gimple-ssa-sprintf.c (format_directive): Same.
            (handle_printf_call): Same.
            * gimple-ssa-warn-alloca.c (pass_walloca::execute): Same.
            * gimple-ssa-warn-restrict.c (maybe_diag_overlap): Same.
            (maybe_diag_access_bounds): Same.  Call gimple_location.
            (check_bounds_or_overlap): Same.
            * trans-mem.c (ipa_tm_scan_irr_block): Remove %K.  Simplify.
            * tree-ssa-ccp.c (pass_post_ipa_warn::execute): Remove %G.
            * tree-ssa-strlen.c (maybe_warn_overflow): Same.
            (maybe_diag_stxncpy_trunc): Same.
            (handle_builtin_stxncpy_strncat): Same.
            (maybe_warn_pointless_strcmp): Same.
            * tree-ssa-uninit.c (maybe_warn_operand): Same.

    gcc/testsuite/ChangeLog:

            * gcc.dg/Wobjsize-1.c: Prune expected output.
            * gcc.dg/Warray-bounds-71.c: New test.
            * gcc.dg/Warray-bounds-71.h: New test header.
            * gcc.dg/Warray-bounds-72.c: New test.
            * gcc.dg/Warray-bounds-73.c: New test.
            * gcc.dg/Warray-bounds-74.c: New test.
            * gcc.dg/Warray-bounds-75.c: New test.
            * gcc.dg/Wfree-nonheap-object-4.c: Adjust expected output.
            * gcc.dg/Wfree-nonheap-object-5.c: New test.
            * gcc.dg/Wfree-nonheap-object-6.c: New test.
            * gcc.dg/pragma-diag-10.c: New test.
            * gcc.dg/pragma-diag-9.c: New test.
            * gcc.dg/uninit-suppress_3.c: New test.
            * gcc.dg/pr79214.c: Xfail tests.
            * gcc.dg/tree-ssa/builtin-sprintf-warn-27.c: New test.
            * gcc.dg/format/c90-printf-1.c: Adjust expected output.

[Bug tree-optimization/98512] [11/12 Regression] “#pragma GCC diagnostic ignored” ineffective in conjunction with alias attribute

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98512

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |12.0
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED
      Known to fail|11.0                        |11.2.0

--- Comment #13 from Martin Sebor <msebor at gcc dot gnu.org> ---
Fixed in GCC 12.  The patch is not suitable for backporting to release
branches.