From: Florian Weimer <fweimer@redhat.com>
To: Rich Felker <dalias@libc.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Andy Lutomirski <luto@kernel.org>,
tg@mirbsd.de, Linus Torvalds <torvalds@linux-foundation.org>,
X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
Mike Frysinger <vapier@gentoo.org>,
"H. J. Lu" <hjl.tools@gmail.com>,
x32@buildd.debian.org, Arnd Bergmann <arnd@arndb.de>,
Will Deacon <will.deacon@arm.com>
Subject: Re: Can we drop upstream Linux x32 support?
Date: Fri, 14 Dec 2018 12:42:34 +0100 [thread overview]
Message-ID: <875zvwibbp.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <20181213162828.GW23599@brightrain.aerifal.cx> (Rich Felker's message of "Thu, 13 Dec 2018 11:28:28 -0500")
* Rich Felker:
> On Thu, Dec 13, 2018 at 05:04:59PM +0100, Florian Weimer wrote:
>> * Rich Felker:
>>
>> >> If the compiler can handle the zeroing, that would be great, though not
>> >> sure how (some __attribute__((zero)) which generates a type constructor
>> >> for such structure; it kind of departs from what the C language offers).
>> >
>> > The compiler fundamentally can't. At the very least it would require
>> > effective type tracking, which requires shadow memory and is even more
>> > controversial than -fstrict-aliasing (because in a sense it's a
>> > stronger version thereof).
>>
>> It's possible to do it with the right types. See _Bool on 32-bit Darwin
>> PowerPC for an example, which is four bytes instead of the usual one.
>>
>> Similarly, we could have integer types with trap representations.
>> Whether it is a good idea is a different matter, but the amount of
>> compiler magic required is actually limited.
>
> If you do this you just have LP64 with value range restricted to
> 32-bit.
You have to a type different from long int for the relevant struct
fields. This type would have zero padding.
Florian
next prev parent reply other threads:[~2018-12-14 11:42 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-11 1:23 Can we drop upstream Linux x32 support? Andy Lutomirski
2018-12-11 1:40 ` Linus Torvalds
2018-12-11 2:22 ` hpa
2018-12-11 8:16 ` Florian Weimer
2018-12-11 21:53 ` Thorsten Glaser
2018-12-11 23:22 ` Andy Lutomirski
2018-12-11 23:35 ` Thorsten Glaser
2018-12-11 23:55 ` Arnd Bergmann
2018-12-12 2:24 ` Andy Lutomirski
2018-12-12 2:33 ` Thorsten Glaser
2018-12-12 9:04 ` Arnd Bergmann
2018-12-12 18:14 ` Joseph Myers
2018-12-12 18:50 ` Ivan Ivanov
2018-12-12 19:12 ` Andy Lutomirski
2018-12-12 19:18 ` Ivan Ivanov
2018-12-12 16:39 ` Andy Lutomirski
2018-12-12 16:52 ` Rich Felker
2018-12-12 18:03 ` Andy Lutomirski
2018-12-13 12:40 ` Catalin Marinas
2018-12-13 15:57 ` Rich Felker
2018-12-13 16:04 ` Florian Weimer
2018-12-13 16:28 ` Rich Felker
2018-12-14 11:42 ` Florian Weimer [this message]
2018-12-14 16:13 ` Rich Felker
2018-12-13 18:42 ` Joseph Myers
2018-12-15 4:53 ` Thorsten Glaser
2018-12-11 23:38 ` Rich Felker
2018-12-11 23:40 ` Maciej W. Rozycki
2018-12-13 14:38 ` Olof Johansson
2018-12-13 15:46 ` Lance Richardson
2018-12-13 16:11 ` Richard Purdie
2018-12-11 3:14 ` H.J. Lu
2018-12-11 5:35 ` Andy Lutomirski
2018-12-11 9:02 ` Arnd Bergmann
2018-12-11 11:32 ` Catalin Marinas
2018-12-11 11:37 ` Florian Weimer
2018-12-11 11:52 ` Catalin Marinas
2018-12-11 5:46 ` Christian Brauner
2018-12-11 10:29 ` John Paul Adrian Glaubitz
2018-12-11 10:37 ` Florian Weimer
2018-12-11 10:44 ` John Paul Adrian Glaubitz
2018-12-11 21:59 ` Thorsten Glaser
2018-12-11 23:33 ` Rich Felker
2018-12-13 5:03 ` Kevin Easton
2018-12-13 9:05 ` Richard Weinberger
2018-12-13 12:12 ` Kevin Easton
2018-12-14 14:38 ` David Laight
2018-12-14 15:17 ` Richard Weinberger
2018-12-13 16:02 ` Rich Felker
2018-12-14 14:13 ` Bernd Petrovitsch
2018-12-14 16:17 ` Rich Felker
2018-12-14 16:29 ` Bernd Petrovitsch
2018-12-14 16:38 ` Florian Weimer
2018-12-14 16:55 ` Rich Felker
2018-12-14 18:58 ` Andy Lutomirski
2018-12-14 19:59 ` Lance Richardson
2018-12-14 20:13 ` Linus Torvalds
2018-12-14 21:27 ` Andy Lutomirski
2018-12-14 21:16 ` Thomas Schöbel-Theuer
2018-12-14 21:24 ` Andy Lutomirski
2018-12-14 21:41 ` Thomas Schöbel-Theuer
2018-12-15 7:41 ` Thomas Schoebel-Theuer
2018-12-15 15:30 ` Andy Lutomirski
2019-01-09 12:41 ` Florian Weimer
2019-01-09 16:02 ` Rich Felker
2019-01-22 13:34 ` Enrico Weigelt, metux IT consult
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=875zvwibbp.fsf@oldenburg2.str.redhat.com \
--to=fweimer@redhat.com \
--cc=arnd@arndb.de \
--cc=bp@alien8.de \
--cc=catalin.marinas@arm.com \
--cc=dalias@libc.org \
--cc=hjl.tools@gmail.com \
--cc=hpa@zytor.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=peterz@infradead.org \
--cc=tg@mirbsd.de \
--cc=torvalds@linux-foundation.org \
--cc=vapier@gentoo.org \
--cc=will.deacon@arm.com \
--cc=x32@buildd.debian.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).