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From: "xry111 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/111256] Wrong code at -O2/3/s since r10-1615-g75efe9cb1f8
Date: Thu, 31 Aug 2023 09:12:30 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111256

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |xry111 at gcc dot gnu.org
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #1 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
In the 2nd iteration of "for (; h <=3D 3; h =3D fn3() + h)" the code uses
uninitialized value:

$ clang t.c -O0 -fsanitize=3Dmemory -g
$ ./a.out=20
=3D=3D76055=3D=3DWARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x56392dea5370 in main /home/xry111/t.c:31:5
    #1 0x7f9671e27f59 in __libc_start_call_main
/home/xry111/sources/lfs/glibc-2.38/csu/../sysdeps/nptl/libc_start_call_mai=
n.h:58:16
    #2 0x7f9671e28024 in __libc_start_main@GLIBC_2.2.5
/home/xry111/sources/lfs/glibc-2.38/csu/../csu/libc-start.c:360:3
    #3 0x56392de0f2d0 in _start
/home/xry111/sources/lfs/glibc-2.38/csu/../sysdeps/x86_64/start.S:115

SUMMARY: MemorySanitizer: use-of-uninitialized-value /home/xry111/t.c:31:5 =
in
main
Exiting

Thus invalid.=