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Re: ARC vs. generic sigaction (was Re: [PATCH 08/21] ARC: Linux Syscall Interface)
- From: Florian Weimer <fweimer at redhat dot com>
- To: Vineet Gupta <vineet dot gupta1 at synopsys dot com>
- Cc: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, Joseph Myers <joseph at codesourcery dot com>, "libc-alpha\@sourceware.org" <libc-alpha at sourceware dot org>, "linux-snps-arc\@lists.infradead.org" <linux-snps-arc at lists dot infradead dot org>
- Date: Thu, 03 Jan 2019 14:10:50 +0100
- Subject: Re: ARC vs. generic sigaction (was Re: [PATCH 08/21] ARC: Linux Syscall Interface)
- References: <1545167083-16764-1-git-send-email-vgupta@synopsys.com> <1545167083-16764-9-git-send-email-vgupta@synopsys.com> <alpine.DEB.2.21.1812182324560.30183@digraph.polyomino.org.uk> <5f512e48-e7fc-2233-febd-2e6a8bc2311b@synopsys.com> <05069752-0a66-d6ca-e249-5c702eec4e99@synopsys.com> <17fcd9f0-9843-8700-c936-7ab1eb8f2fd2@linaro.org> <906931a6-a281-8994-718f-da203890e7e9@synopsys.com> <4c3af320-cf35-f914-8bc3-a4c290b8e12b@linaro.org> <87va3oqsks.fsf@oldenburg2.str.redhat.com> <C2D7FE5348E1B147BCA15975FBA2307501464238AD@US01WEMBX2.internal.synopsys.com>
* Vineet Gupta:
> On 12/20/18 4:40 AM, Florian Weimer wrote:
>> * Adhemerval Zanella:
>>
>>> The only advantage of using a larger sigset_t from glibc standpoint is if
>>> kernel ever change it maximum number of supported signals it would not be
>>> a ABI change (it would be if glibc provided sigset_t need to be extended).
>> It's not just the kernel. We might want to restore additional state in
>> sigsetjmp, and historically, the excess signal space in sigset_t has
>> provided a way to do that even if there is no other space left in the
>> jump buffer.
>
> And that additional state is architectural state (more FPU regs etc
> etc) or something libc generic. On both counts, that doesn't sound
> like a clean interface design !
Sure, setjmp/longjmp is quite horrible as an interface, considering that
register files do evolve. But it's what we have in C, and it's good to
have at least some extension space there (but it could be expressed in a
better way, definitely).
Thanks,
Florian