Re: siginfo_t missing member si_band

[Christopher Faylor <cgf-use-the-mailinglist-please at cygwin dot com>]

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.

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