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Re: glibc 2.21 - Machine maintainers, please test your machines.
- From: Torvald Riegel <triegel at redhat dot com>
- To: Andreas Schwab <schwab at suse dot de>
- 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 16:33:49 +0100
- Subject: Re: glibc 2.21 - Machine maintainers, please test your machines.
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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?
For glibc, the accesses which might not be aligned as promised are to
either the private field, or in the form of atomic operations. Do you
seem examples of badness happening in both cases, or is this more a case
of not being able to prove absence of badness (which would be a valid
concern too).
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?
- 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.