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Message-ID: <525DB015.1010707@cs.utoronto.ca>
Date: Tue, 15 Oct 2013 17:13:57 -0400
From: Ryan Johnson <ryan DOT johnson AT cs DOT utoronto DOT ca>
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To: cygwin AT cygwin DOT com
Subject: Re: siginfo_t missing member si_band
References: <525D55B3 DOT 3050002 AT cs DOT utoronto DOT ca> <20131015194242 DOT GA2368 AT ednor DOT casa DOT cgf DOT cx>
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On 15/10/2013 3:42 PM, Christopher Faylor wrote:
> On Tue, Oct 15, 2013 at 10:48:19AM -0400, Ryan Johnson wrote:
>> Hi all,
>>
>> While trying to build python3 for cygwin, I kept encountering the
>> following error message:
>>
>> ./Modules/signalmodule.c: In function ?fill_siginfo?:
>> ./Modules/signalmodule.c:745:60: error: ?siginfo_t? has no member named
>> ?si_band?
>> PyStructSequence_SET_ITEM(result, 6, PyLong_FromLong(si->si_band));
>> ^
>> Include/tupleobject.h:62:75: note: in definition of macro
>> ?PyTuple_SET_ITEM?
>> #define PyTuple_SET_ITEM(op, i, v) (((PyTupleObject *)(op))->ob_item[i]
>> = v)
>> ^
>> ./Modules/signalmodule.c:745:5: note: in expansion of macro
>> ?PyStructSequence_SET_ITEM?
>> PyStructSequence_SET_ITEM(result, 6, PyLong_FromLong(si->si_band));
>>
>> As far as I can tell, siginfo_t::si_band is mandated by POSIX.1-2001,
>> and required for proper handling of SIGPOLL. The latter seems to
>> correspond to async I/O with poll(2). I'm pretty sure cygwin doesn't
>> support async I/O, but shouldn't the struct member at least exist, to
>> avoid breaking code that assumes its existence? The alternative is to
>> patch python3 locally so its os.sigwaitinfo function no longer touches
>> si_band, or to file a bug upstream so that the module's configury tests
>> for its existence before using it.
>>
>> Thoughts?
> Sure.  I question the utility of lying in a structure about the
> availability of an unimplemented feature.  If something is specifically
> expecting the structure member to exist it seems like it would be
> expecting it to do something.
So that would be a vote for filing a bug upstream with python's FFI 
interface to signal handling? Fair enough.

Ryan


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