From: Jonathan Wakely <jwakely@redhat.com>
To: "François Dumont" <frs.dumont@gmail.com>
Cc: "libstdc++" <libstdc++@gcc.gnu.org>
Subject: Re: PR 108846 regression
Date: Mon, 3 Apr 2023 21:06:39 +0100 [thread overview]
Message-ID: <CACb0b4niT5JJqztD3pM1ALbgmk1SETomCs4Nkc52B0TOK55p+A@mail.gmail.com> (raw)
In-Reply-To: <ab398aa1-4384-714d-6cf2-238549799722@gmail.com>
On Mon, 3 Apr 2023 at 21:00, François Dumont via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> After a full rebuild and run of testsuite based on master I have this
> regression:
>
> FAIL: 23_containers/vector/bool/allocator/copy.cc (test for excess errors)
> Excess errors:
> /home/fdumont/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/stl_algobase.h:437:
> warning: 'void* __builtin_memmove(void*, const void*, long unsigned
> int)' writing between 9 and 9223372036854775807 bytes into a region of
> size 8 overflows the destination [-Wstringop-overflow=]
>
> It comes from the change related to PR 108846, revision
> 822a11a1e642e0abe92a996e7033a5066905a447
>
> The compiler seems to have enough info to find out that destination
> memory area is 8 bytes large but not enough to see that _Num is 1 and so
> never going to call the __builtin_memmove. Maybe a compiler bug.
Yes, it's a compiler bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109353
> I'm working on a patch to restore previous code when src and dst pointer
> types are the same.
How will that avoid the PR 108846 problem of overwriting tail padding?
>
> But I won't be able to continue my work on it before Wednesday so I
> prefer to let you know just in case you would like to fix it before that
> and maybe differently.
>
> François
>
>
next prev parent reply other threads:[~2023-04-03 20:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-03 19:59 François Dumont
2023-04-03 20:06 ` Jonathan Wakely [this message]
2023-04-05 17:03 ` François Dumont
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