On Jul 26 01:51, Mark Geisert wrote: > Hi Corinna, > > On Thu, 26 Jul 2018, Corinna Vinschen wrote: > > On Jul 25 15:06, Yaakov Selkowitz wrote: > > > > From discussion on IRC: > > > > > > <yselkowitz> corinna, just sent a patch for _POSIX_ASYNCHRONOUS_IO as a > > > follow-up to the AIO feature, but am still wondering about > > > _[POSIX|PC]_ASYNC_IO > > > [snip] > > > <corinna> in terms of _PC_ASYNC_IO, the test might be a bit tricky > > > <corinna> let me check > > > <corinna> actually, no > > > <corinna> it's easy > > > <corinna> Mark implemented the stuff with pread/pwrite only on disk files > > > <corinna> but otherwise it's device independent in that he implemented a > > > workaround for pipes and stuff > > > <corinna> so, in theory we can just return 1 > > > > > > I'm not sure how to test this atm, but based on the above I have made > > > the following patch so this doesn't get lost. > > > > > > Yaakov Selkowitz (1): > > > Cygwin: fpathconf: update _PC_ASYNC_IO return value > > > > > > winsup/cygwin/fhandler.cc | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > -- > > > 2.17.1 > > > > Mark? Any comment you want to make? > > Thanks for asking. Your characterization of my implementation is correct. > The intent is for aio_* async I/O to be supported on all descriptors. On > the most useful case of binary local disk files, inline pread|pwrite is > used. But I wanted to make sure the AIO interface would do the right thing > on other kinds of descriptors without bothering the user about it. > > So if the intent of the _PC_ASYNC_IO flag is to say that async I/O is > supported generally, I do think setting it to 1 is appropriate. That is, > if it's talking about the aio_* interfaces. If there's an O_ASYNC defined > for app coders, my recent contribution doesn't address that at all.
Good question. O_ASYNC is a BSD invention, and it's not defined in POSIX at all. Since we're in POSIX territory, _PC_ASYNC_IO and _POSIX_ASYNC_IO can only refer to async io as implemented by your new aio code: - _POSIX_ASYNCHRONOUS_IO defines if the implementation supports async io at all. - _POSIX_ASYNC_IO defines if the file in question supports async io. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
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