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From: "bic60176 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/115127] New: [12/13/14 Regression] passing zero to
 __builtin_ctz() check missing
Date: Fri, 17 May 2024 07:22:32 +0000
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X-Bugzilla-Component: sanitizer
X-Bugzilla-Version: 12.3.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115127

            Bug ID: 115127
           Summary: [12/13/14 Regression] passing zero to __builtin_ctz()
                    check missing
           Product: gcc
           Version: 12.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bic60176 at gmail dot com
                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
  Target Milestone: ---

Created attachment 58220
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D58220&action=3Dedit
test case

OS: Ubuntu 22.04.3 LTS
We found that UBSAN missed checking if zero is passed to __builtin_ctz() wh=
en
compiling with gcc-12.3.0, gcc-13.2.0, gcc-14.1.0.

$ ../compiler-builds/gcc-12.3.0_build/bin/gcc -fsanitize=3Dundefined -g -lg=
cc_s
-I/home/csmith/include/csmith-2.3.0 testcase.c -o exec

$ timeout 1s ./exec 2>exec.err

$ cat exec.err

$ ../compiler-builds/gcc-11.4.0_build/bin/gcc -fsanitize=3Dundefined -g -lg=
cc_s
-I/home/csmith/include/csmith-2.3.0 testcase.c -o exec

$ timeout 1s ./exec 2>exec.err

$ cat exec.err
test1_176.c:202:83: runtime error: passing zero to ctz(), which is not a va=
lid
argument test1_176.c:202: runtime error: passing zero to ctz(), which is no=
t a
valid argument test1_176.c:202: runtime error: passing zero to ctz(), which=
 is
not a valid argument test1_176.c:202: runtime error: passing zero to ctz(),
which is not a valid argument test1_176.c:202: runtime error: passing zero =
to
ctz(), which is not a valid argument test1_176.c:202: runtime error: passing
zero to ctz(), which is not a valid argument=