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From: "dcb314 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/109184] New: csmith: really old bug with -O3
Date: Sat, 18 Mar 2023 11:21:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109184

            Bug ID: 109184
           Summary: csmith: really old bug with -O3
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

Created attachment 54701
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54701&action=3Dedit
C source code

For the attached C code, compiled with -O2 and -O3, produces different answ=
ers:

$ ~/gcc/results/bin/gcc -w -O2 -fno-strict-aliasing bug897.c
$ ./a.out 1 > 1
$ $ ~/gcc/results/bin/gcc -w -O3 -fno-strict-aliasing bug897.c
$ ./a.out 1 > 2
$ diff 1 2 | head
2038c2038
< ...checksum after hashing g_1731[i][j] : 351CD463
---
> ...checksum after hashing g_1731[i][j] : 7739D31E
2040c2040
< ...checksum after hashing g_1731[i][j] : 791FAA71
---
> ...checksum after hashing g_1731[i][j] : FEBF8F12

The bug seems to exist since sometime before 20220403, nearly a year ago.

Flag -ftrivial-auto-var-init=3Dzero doesn't seem to help.=