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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/108085] New: gcc trunk's ASAN at -O3 missed a
 stack-use-after-scope
Date: Tue, 13 Dec 2022 16:08:37 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: sanitizer
X-Bugzilla-Version: 13.0
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X-Bugzilla-Who: shaohua.li at inf dot ethz.ch
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108085

            Bug ID: 108085
           Summary: gcc trunk's ASAN at -O3 missed a stack-use-after-scope
           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 failed to report the stack-use-after-sc=
ope,
other opt levels detected it successfully.

GCC-8 works fine.=20
Clang at all optimization levels reported it.

Compiler explorer: https://godbolt.org/z/jbsThYWa6

% cat a.c
int a;
void b() {
  int c[1];
  c;
}
int main() {
  int d[1]=3D{1};
  int *e =3D d;
  a =3D 0;
  for (; a <=3D 5; ++a) {
    int f[1]=3D{};
    e =3D f;
    a || (b(), 1);
  }
  return *e;
}
%
% gcc-tk -O2 -fsanitize=3Daddress -g 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
=3D=3D780198=3D=3DERROR: AddressSanitizer: stack-use-after-scope on address
0x7f2307600030 at pc 0x0000004011c5 bp 0x7ffdd19ecd80 sp 0x7ffdd19ecd78
READ of size 4 at 0x7f2307600030 thread T0
    #0 0x4011c4 in main /a.c:15
    #1 0x7f2309f41082 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId:
1878e6b475720c7c51969e69ab2d276fae6d1dee)
    #2 0x40126d in _start (/a.out+0x40126d)

Address 0x7f2307600030 is located in stack of thread T0 at offset 48 in fra=
me
    #0 0x4010bf in main /a.c:6

  This frame has 3 object(s):
    [32, 36) 'd' (line 7)
    [48, 52) 'f' (line 11) <=3D=3D Memory access at offset 48 is inside this
variable
    [64, 68) 'c' (line 3)
...
%
% gcc-tk -O3 -fsanitize=3Daddress -g a.c && ./a.out
%=