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From: Sam James <sam@gentoo.org>
To: =?utf-8?Q?Fran=C3=A7ois?= Dumont <frs.dumont@gmail.com>
Cc: libstdc++ <libstdc++@gcc.gnu.org>,  gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] Fix -Wstringop-overflow warning in
 23_containers/vector/types/1.cc
In-Reply-To: <4657346e-3046-424a-be1d-32a7eaecae32@gmail.com>
 (=?utf-8?Q?=22Fran=C3=A7ois?=
	Dumont"'s message of "Mon, 27 May 2024 22:07:42 +0200")
Organization: Gentoo
References: <4657346e-3046-424a-be1d-32a7eaecae32@gmail.com>
Date: Mon, 27 May 2024 21:18:12 +0100
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Fran=C3=A7ois Dumont <frs.dumont@gmail.com> writes:

> In C++98 this test fails with:

For this, and your other -Wfree-nonheap-object patches, could you see if
it helps with any of the bugs reported for both -Wstringop-overflow and
-Wfree-nonheap-object in libstdc++? There's a bunch of (possible) dupes
that it'd be worth tagging if any of them are applicable.

>
> Excess errors:
> /home/fdumont/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits=
/stl_algobase.h:452:
> warning: 'void* __builtin_memcpy(void*, const void*, long unsigned
> int)' writing between 2 and 9223372036854775806 bytes into a region of
> size 0 overflows the destination [-Wstringop-overflow=3D]
>
> The attached patch avoids this warning.
>
> =C2=A0=C2=A0=C2=A0 libstdc++: Fix -Wstringop-overflow warning coming from=
 std::vector
>
> =C2=A0=C2=A0=C2=A0 Make vector<>::_M_range_insert implementation more tra=
nsparent to
> the compiler checks.
>
> =C2=A0=C2=A0=C2=A0 Extend local copies of members to the whole method sco=
pe so that
> all branches benefit
> =C2=A0=C2=A0=C2=A0 from those.
>
> =C2=A0=C2=A0=C2=A0 libstdc++-v3/ChangeLog:
>
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * incl=
ude/bits/vector.tcc
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 (std::=
vector<>::_M_range_insert(iterator, _FwdIt, _FwdIt,
> forward_iterator_tag)):
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Use lo=
cal copies of members to call the different algorithms.
>
> Ok to commit if all tests passes ?
>
> Fran=C3=A7ois
>
> [2. text/plain; vector_range_insert_patch.txt]...