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Re: glibc 2.21 - Machine maintainers, please test your machines.
- From: Andreas Schwab <schwab at suse dot de>
- To: Torvald Riegel <triegel at redhat dot com>
- Cc: "H.J. Lu" <hjl dot tools at gmail dot com>, Chris Metcalf <cmetcalf at ezchip dot com>, "Carlos O'Donell" <carlos at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>, David Miller <davem at davemloft dot net>, Richard Henderson <rth at redhat dot com>, Mike Frysinger <vapier at gentoo dot org>, "Joseph S. Myers" <joseph at codesourcery dot com>, Kaz Kojima <kkojima at rr dot iij4u dot or dot jp>, Thomas Schwinge <thomas at codesourcery dot com>, Marcus Shawcroft <marcus dot shawcroft at linaro dot org>, Chung-Lin Tang <chunglin_tang at mentor dot com>, Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>, Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>
- Date: Mon, 26 Jan 2015 16:52:31 +0100
- Subject: Re: glibc 2.21 - Machine maintainers, please test your machines.
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Torvald Riegel <triegel@redhat.com> writes:
> On Mon, 2015-01-26 at 16:03 +0100, Andreas Schwab wrote:
>> The compiler can simplify operations based on the known alignment of
>> objects. This is like any other undefined behaviour.
>
> Is your concern regarding glibc code (ie, sem_*()) or code outside
> glibc?
It doesn't matter. If you have a type with 8 byte alignment, but the
object has only 4 byte alignment you get undefined behaviour.
> For code outside of glibc, I'm not sure something can actually happen.
> If an application picks up the new semaphore.h, sem_t will be
> 8B-aligned. If not, then not. I don't think this can be partially
> 8B/4B-aligned, or can it?
You are changing the ABI. Anything can happen.
Andreas.
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
- References:
- glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.
- Re: glibc 2.21 - Machine maintainers, please test your machines.