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From: "qrzhang at gatech dot edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/108845] New: Unnecessary signed integer overflow
 checks
Date: Sat, 18 Feb 2023 19:24:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108845

            Bug ID: 108845
           Summary: Unnecessary signed integer overflow checks
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: qrzhang at gatech dot edu
                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: ---

When compiled with "gcc -fsanitize=3Dsigned-integer-overflow -O3" (reproduc=
ible
on the latest trunk version), Gcc will produce ".UBSAN_CHECK_SUB" checks for
the following code.

=3D=3D=3D=3D=3D=3D=3D
void printf();
void main() {
  int a;
  for (a =3D 0; a !=3D -3; a--)
    printf("%d\n", a);
}
=3D=3D=3D=3D=3D=3D=3D=3D


I noticed that clang could indeed optimize this program to three printf() c=
alls
with "-fsanitize=3Dsigned-integer-overflow -O3". Therefore, no overflow che=
cks
are needed.

Is this behavior in GCC expected? Thanks!=