From: Jonathan Wakely <jwakely@redhat.com>
To: Andreas Schwab <schwab@suse.de>
Cc: Jakub Jelinek via Gcc-patches <gcc-patches@gcc.gnu.org>,
Jan Hubicka <hubicka@ucw.cz>, Jakub Jelinek <jakub@redhat.com>,
"libstdc++" <libstdc++@gcc.gnu.org>
Subject: Re: [libstdc++] Improve M_check_len
Date: Tue, 20 Jun 2023 11:45:46 +0100 [thread overview]
Message-ID: <CACb0b4=VeTb9WyP-Su0PWYEQj_9240T_2U-QLGRQKU0kz7SZVg@mail.gmail.com> (raw)
In-Reply-To: <mvmwmzy1r3d.fsf@suse.de>
[-- Attachment #1: Type: text/plain, Size: 1035 bytes --]
On Tue, 20 Jun 2023 at 09:21, Andreas Schwab wrote:
> On Jun 20 2023, Jakub Jelinek via Gcc-patches wrote:
>
> > Is it safe even on 64bit targets? I mean, doesn't say PowerPC already
> allow
> > full 64-bit virtual address space? The assumption that one can't have
> > more than half of virtual address space allocations is true right now at
> > least on x86-64, aarch64 and others, but isn't that something that can
> > change with newer versions of CPUs without the need to recompile
> > applications (add another level or two of page tables)?
>
> At least s390 can allocate more than half the address space. That
> triggered a failure in gawk.
>
Is PTRDIFF_MAX large enough to represent the difference between any two
pointers?
What we're considering for libstdc++ is treating PTRDIFF_MAX as an upper
limit on allocation size. If there are targets that can really allocate a
2^63 byte array, they won't be able to represent the difference between the
first element and the last element unless ptrdiff_t is wider than 64 bits.
next prev parent reply other threads:[~2023-06-20 10:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-18 18:27 Jan Hubicka
2023-06-19 10:12 ` Jonathan Wakely
2023-06-19 11:05 ` Jan Hubicka
2023-06-19 11:20 ` Jakub Jelinek
2023-06-19 15:13 ` Jonathan Wakely
2023-06-19 15:14 ` Jonathan Wakely
2023-06-19 15:35 ` Jonathan Wakely
2023-06-20 7:50 ` Jan Hubicka
2023-06-20 8:05 ` Jan Hubicka
2023-06-20 8:07 ` Jakub Jelinek
2023-06-20 8:21 ` Andreas Schwab
2023-06-20 10:45 ` Jonathan Wakely [this message]
2023-06-20 10:50 ` Jonathan Wakely
2023-06-19 16:14 ` Jan Hubicka
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