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From: "shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/109330] New: ASAN since GCC-9 missed a
 stack-use-after-scope at -O3
Date: Wed, 29 Mar 2023 08:18:46 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: sanitizer
X-Bugzilla-Version: 13.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109330

            Bug ID: 109330
           Summary: ASAN since GCC-9 missed a stack-use-after-scope at -O3
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxi=
n at gcc dot gnu.org
  Target Milestone: ---

For the following code, ASAN at -O3 since GCC-9 missed the use-after-scope.
I checked the code and found that `*f=3D*g` and `return *f` were not optimi=
zed
away by the compiler.

Compiler explorer: https://godbolt.org/z/c96a6jWrY

% cat a.c
int a, c, d;
char b, e;
int main() {
  int *f =3D &a, *g =3D &c;
h:
  &g;
  for (; 0;)
    goto h;
  d =3D 0;
  for (; d <=3D 3; d++) {
    int i =3D *f;
    b && (e =3D 1);
    f =3D &i;
  }
  *f =3D *g;
  return *f;
}
% gcc-tk -O3 -fsanitize=3Daddress a.c && ./a.out
%
% gcc-8 -O3 -fsanitize=3Daddress a.c && ./a.out
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
=3D=3D1=3D=3DERROR: AddressSanitizer: stack-use-after-scope on address 0x7f=
fd6b6b94d0
at pc 0x0000004008e1 bp 0x7ffd6b6b94a0 sp 0x7ffd6b6b9498
WRITE of size 4 at 0x7ffd6b6b94d0 thread T0
    #0 0x4008e0 in main /a.c:15
...
%=