[Bug middle-end/102453] New: buffer overflow by atomic built-ins not diagnosed

[Bug middle-end/102453] New: buffer overflow by atomic built-ins not diagnosed

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102453

            Bug ID: 102453
           Summary: buffer overflow by atomic built-ins not diagnosed
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

The buffer overflow by the straight assignment in f() below is diagnosed as
expected but the equivalent overflow by the atomic built-in in g() is not even
though both should be.  The problem is simply that due to an oversight, the
access warnings lack support for atomic built-ins.

$ cat y.c && gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout y.c
extern _Atomic char x;

void f (void)
{
  long *p = (long*)&x;

  *p = 0;
}

void g (void)
{
  long *p = (long*)&x;

  __atomic_store_n (p, 0, 0);
}
y.c: In function ‘f’:
y.c:7:3: warning: array subscript ‘long int[0]’ is partly outside array bounds
of ‘_Atomic char[1]’ [-Warray-bounds]
    7 |   *p = 0;
      |   ^~
y.c:1:21: note: object ‘x’ of size 1
    1 | extern _Atomic char x;
      |                     ^

;; Function f (f, funcdef_no=0, decl_uid=1979, cgraph_uid=1, symbol_order=0)

void f ()
{
  <bb 2> [local count: 1073741824]:
  MEM[(long int *)&x] = 0;
  return;

}



;; Function g (g, funcdef_no=1, decl_uid=1983, cgraph_uid=2, symbol_order=1)

void g ()
{
  <bb 2> [local count: 1073741824]:
  __atomic_store_8 (&x, 0, 0); [tail call]
  return;

}

[Bug middle-end/102453] buffer overflow by atomic built-ins not diagnosed

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102453

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|UNCONFIRMED                 |ASSIGNED
           Keywords|                            |diagnostic
             Blocks|                            |56456
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-09-22


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56456
[Bug 56456] [meta-bug] bogus/missing -Warray-bounds

[Bug middle-end/102453] buffer overflow by atomic built-ins not diagnosed

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102453

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

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

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Patch: https://gcc.gnu.org/pipermail/gcc-patches/2021-October/581396.html

[Bug middle-end/102453] buffer overflow by atomic built-ins not diagnosed

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102453

--- Comment #2 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:88b504b7a8c5affb0ffa97990d22af2b199e36ed

commit r12-4725-g88b504b7a8c5affb0ffa97990d22af2b199e36ed
Author: Martin Sebor <msebor@redhat.com>
Date:   Tue Oct 26 14:34:16 2021 -0600

    Detect overflow by atomic functions [PR102453].

    Resolves:
    PR middle-end/102453 - buffer overflow by atomic built-ins not diagnosed

    gcc/ChangeLog:

            PR middle-end/102453
            * gimple-ssa-warn-access.cc (pass_waccess::check_atomic_builtin):
New.
            (pass_waccess::check_atomic_builtin): Call it.

    gcc/testsuite/ChangeLog:

            PR middle-end/102453
            * gcc.dg/Warray-bounds-90.c: New test.
            * gcc.dg/Wstringop-overflow-77.c: New test.
            * gcc.dg/Wstringop-overflow-78.c: New test.
            * gcc.dg/Wstringop-overflow-79.c: New test.
            * gcc.dg/Wstringop-overflow-80.c: New test.
            * c-c++-common/gomp/atomic-4.c: Avoid an out-of-bounds access.

[Bug middle-end/102453] buffer overflow by atomic built-ins not diagnosed

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102453

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED
   Target Milestone|---                         |12.0

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
Done in r12-4725.