From: Andreas Jaeger <aj@suse.de>
To: libc-hacker@sources.redhat.com
Subject: Re: BZ 5012: Add FAQ entry for compiling with optimization
Date: Fri, 22 Feb 2008 09:00:00 -0000 [thread overview]
Message-ID: <m3r6f5fjs8.fsf@gromit.moeb> (raw)
In-Reply-To: <87abq4poyw.fsf@suse.de> (Andreas Jaeger's message of "Sat, 27 Oct 2007 17:16:39 +0200")
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Andreas Jaeger <aj@suse.de> writes:
> The following adds an entry to the FAQ to mention why optimization is
> needed for compiling glibc. Ok to commit?
Is it ok to commit this one?
Andreas
> Andreas
>
> 2007-10-27 Andreas Jaeger <aj@suse.de>,
> Carlos O'Donell <carlos@systemhalted.org>
>
> [BZ #5012]
> * FAQ.in: Describe why glibc needs to be compiled with
> optimization.
>
> ============================================================
> Index: FAQ.in
> --- FAQ.in 8 Apr 2005 20:59:50 -0000 1.137
> +++ FAQ.in 27 Oct 2007 15:14:50 -0000
> @@ -387,6 +387,32 @@ yourself. Please remember that for each
> patches required to get glibc HEAD into a runnable state. The best course
> of action is to determine if you have all the required patches.
>
> +?? Why do I get:
> + `#error "glibc cannot be compiled without optimization"',
> + when trying to compile GNU libc with GNU CC?
> +
> +{AJ,CO} There are a couple of reasons why the GNU C library will not work
> +correctly if it is not complied with optimzation.
> +
> +In the early startup of the dynamic loader (_dl_start), before
> +relocation of the PLT, you cannot make function calls. You must inline
> +the functions you will use during early startup, or call compiler
> +builtins (__builtin_*).
> +
> +Without optimizations enabled GNU CC will not inline functions. The
> +early startup of the dynamic loader will make function calls via an
> +unrelocated PLT and crash.
> +
> +Without auditing the dynamic linker code it would be difficult to remove
> +this requirement.
> +
> +Another reason is that nested functions must be inlined in many cases to
> +avoid executable stacks.
> +
> +In practice there is no reason to compile without optimizations, therefore
> +we require that GNU libc be compiled with optimizations enabled.
> +
> +
> ? Installation and configuration issues
>
> ?? Can I replace the libc on my Linux system with GNU libc?
> @@ -1685,6 +1711,7 @@ Answers were given by:
> {AO} Alexandre Oliva, <aoliva@redhat.com>
> {BH} Bruno Haible, <haible@clisp.cons.org>
> {SM} Steven Munroe, <sjmunroe@us.ibm.com>
> +{CO} Carlos O'Donell, <carlos@systemhalted.org>
> \f
> Local Variables:
> mode:outline
Andreas
--
Andreas Jaeger, Director Platform/openSUSE, aj@suse.de
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
Maxfeldstr. 5, 90409 Nürnberg, Germany
GPG fingerprint = 93A3 365E CE47 B889 DF7F FED1 389A 563C C272 A126
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next prev parent reply other threads:[~2008-02-22 9:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-27 15:16 Andreas Jaeger
2008-02-22 9:00 ` Andreas Jaeger [this message]
2008-02-22 9:09 ` Roland McGrath
2008-02-22 14:34 ` Ulrich Drepper
2008-02-22 14:46 ` Andreas Jaeger
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