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From: Jakub Jelinek via Libc-alpha <libc-alpha@sourceware.org>
To: Martin Sebor <msebor@gmail.com>
Cc: gcc@gcc.gnu.org, libc-alpha@sourceware.org,
	Joseph Myers <joseph@codesourcery.com>
Subject: Re: Failures building glibc with mainline GCC
Date: Fri, 30 Jul 2021 19:02:04 +0200	[thread overview]
Message-ID: <20210730170204.GP2380545@tucnak> (raw)
In-Reply-To: <1bcf4c26-1619-06fa-fd8d-4e944ac6f07a@gmail.com>

On Fri, Jul 30, 2021 at 10:53:28AM -0600, Martin Sebor via Gcc wrote:
> On 7/30/21 9:30 AM, Joseph Myers wrote:
> > There are a lot of failures building glibc with mainline GCC right now
> > <https://sourceware.org/pipermail/libc-testresults/2021q3/008335.html>
> > (previously, there were ICEs building glibc on various architectures, so
> > these might be hard to bisect):
> > 
> > 
> > * x86_64-linux-gnu: "error: array subscript 0 is outside array bounds of
> > '__seg_fs struct pthread * __seg_fs[0]' [-Werror=array-bounds]".  This is
> > the one discussed in
> > <https://gcc.gnu.org/pipermail/gcc/2021-July/236922.html>.
> 
> I submitted a patch for this warning to Glibc:
> https://sourceware.org/pipermail/libc-alpha/2021-July/128829.html
> which is what ultimately precipitated Florian's question.  If null
> pointers to named address spaces are valid I'll adjust GCC to
> avoid the warning for now (as has been discussed, for GCC 12 I'd
> like to redo the logic to detect the problematic null pointer
> arithmetic instead).

They are valid for some address spaces.
See e.g. how gimple.c (check_loadstore) used by
infer_nonnull_range_by_dereference uses a target hook for that:
      /* Some address spaces may legitimately dereference zero.  */
      addr_space_t as = TYPE_ADDR_SPACE (TREE_TYPE (op));
      if (targetm.addr_space.zero_address_valid (as))
        return false;

	Jakub


      reply	other threads:[~2021-07-30 17:02 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 15:30 Failures building glibc with mainline GCC Joseph Myers
2021-07-30 16:19 ` Aldy Hernandez via Libc-alpha
2021-07-30 16:22   ` Jeff Law via Libc-alpha
2021-07-30 16:45   ` Jeff Law via Libc-alpha
2021-07-30 17:28     ` Martin Sebor via Libc-alpha
2021-07-30 20:52   ` Joseph Myers
2021-08-02 20:20     ` Martin Sebor via Libc-alpha
2021-08-03 15:54       ` Joseph Myers
2021-08-03 16:20         ` Martin Sebor via Libc-alpha
2021-08-03 17:21           ` Joseph Myers
2021-08-03 17:39             ` Samuel Thibault via Libc-alpha
2021-08-03 22:33             ` Martin Sebor via Libc-alpha
2021-08-03 20:50           ` Segher Boessenkool
2021-08-03 21:00             ` Joseph Myers
2021-08-03 22:02               ` Segher Boessenkool
2021-08-03 22:59               ` Martin Sebor via Libc-alpha
2021-07-30 16:38 ` Joseph Myers
2021-07-30 16:43   ` Jakub Jelinek via Libc-alpha
2021-07-30 16:53 ` Martin Sebor via Libc-alpha
2021-07-30 17:02   ` Jakub Jelinek via Libc-alpha [this message]

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