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Re: why Glibc does not build with clang?
- From: pinskia at gmail dot com
- To: Andreas Schwab <schwab at linux-m68k dot org>
- Cc: Rich Felker <dalias at libc dot org>, Roland McGrath <roland at hack dot frob dot com>, Konstantin Serebryany <konstantin dot s dot serebryany at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Sat, 24 May 2014 09:22:02 -0700
- Subject: Re: why Glibc does not build with clang?
- Authentication-results: sourceware.org; auth=none
- References: <CAGQ9bdw135gBO+cTQx3Ws1GrRgFsi8-j=Y_mZ=ixebpPzB4gXw at mail dot gmail dot com> <20140523214019 dot DA9FF2C3975 at topped-with-meat dot com> <20140524142902 dot GP507 at brightrain dot aerifal dot cx> <874n0fi6ac dot fsf at igel dot home> <20140524145139 dot GQ507 at brightrain dot aerifal dot cx> <87zji7gnqx dot fsf at igel dot home>
> On May 24, 2014, at 9:11 AM, Andreas Schwab <firstname.lastname@example.org> wrote:
> Rich Felker <email@example.com> writes:
>>> On Sat, May 24, 2014 at 04:46:03PM +0200, Andreas Schwab wrote:
>>> Rich Felker <firstname.lastname@example.org> writes:
>>>> Nested functions are a feature that fundamentally requires producing
>>>> an insecure executable/library (executable-stack flag)
>>> Only if you pass the address of it out of the containing function.
>> That's my "_except_ in cases where the compiler optimizes out that
> That's not the exception, that's the rule. If you never take the
> address of the nested function you never need a trampoline.
Andreas is correct, trampolines are never generated unless you take the address of a nested function. It is not an optimization as it never generated to begin with. Also some abi don't need a trampoline: PPC64v1 for an example.
> Andreas Schwab, email@example.com
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
> "And now for something completely different."