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From: "xry111 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/109446] Possible destination array overflow without
 diagnosis in memcpy
Date: Wed, 12 Apr 2023 08:08:50 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109446

--- Comment #4 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Martin Li=C5=A1ka from comment #3)
> The problem here is that we normally preserve memcpy calls and then
> __interceptor_memcpy is used from the run-time library. However, in this
> case the second argument of memcpy is a known constant and we convert it =
to:
>   MEM <unsigned char[64]> [(char * {ref-all})_7] =3D MEM <unsigned char[6=
4]>
> [(char * {ref-all})&txt];
>=20
> for such an assignment we only check the beginning and the end of the chu=
nk
> and we miss the overflow.

It seems Clang disables this optimization and convert memcpy to __asan_memc=
py
calls if -fsanitize=3Daddress used:

https://godbolt.org/z/dcfadoMYY=