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Re: [PATCH v2][BZ 16852] Do not clobber recvmmsg argument.
- From: "Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>
- To: Ondřej Bílka <neleai at seznam dot cz>
- Cc: Michael Kerrisk <mtk dot manpages at gmail dot com>, David Miller <davem at davemloft dot net>, Andreas Schwab <schwab at linux-m68k dot org>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Wed, 30 Apr 2014 15:35:40 +0200
- Subject: Re: [PATCH v2][BZ 16852] Do not clobber recvmmsg argument.
- Authentication-results: sourceware.org; auth=none
- References: <20140428152937 dot GA1736 at domone dot podge> <87mwf5zcl3 dot fsf at igel dot home> <20140428160420 dot GA23142 at domone dot podge> <20140428 dot 130122 dot 2188782190759376374 dot davem at davemloft dot net> <5360B445 dot 2000408 at gmail dot com> <20140430090724 dot GA10194 at domone dot podge> <5360DBC3 dot 3070307 at gmail dot com>
- Reply-to: mtk dot manpages at gmail dot com
On Wed, Apr 30, 2014 at 1:17 PM, Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
> Hello OndÅej,
>
> On 04/30/2014 11:07 AM, OndÅej BÃlka wrote:
>> On Wed, Apr 30, 2014 at 10:28:53AM +0200, Michael Kerrisk (man-pages) wrote:
>>> On 04/28/2014 07:01 PM, David Miller wrote:
>>>> From: OndÅej BÃlka <neleai@seznam.cz>
>>>> Date: Mon, 28 Apr 2014 18:04:20 +0200
>>>>
>>>>> * sysdeps/unix/sysv/linux/recvmmsg.c (recvmmsg): Do not clobber
>>>>> timeout argument.
>>>>
>>>> It is extremely unfortunate if we've defined this argument as const,
>>>> now you are making it so that the user has no mechanism to get the
>>>> updated timeval other than to define their own syscall stubs.
>>>>
>>>> This is doubly unfortunately since there is absolutely no reason for
>>>> us to have defined the interface different from what the kernel
>>>> actually provides.
>>>
>>> Agreed. Surely, the right fix here is simply to remove the "const"
>>> qualifier from the glibc API?
>>>
>> Now I am also for removing const. Initially I looked to documentation
>> and this was undocumented feature so I was not sure about it.
>
> Yes, my mistake.
Sigh! Now I remember why that timeout behavior didn't get documented:
http://thread.gmane.org/gmane.linux.man/3477/focus=3500
The timeout argument is completely broken, AFAICT. I never did get a
reply from Arnaldo (but, as you can see in the thread, others agreed
tha there's a problem), and then I got distracted :-{.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/