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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(+) -- 2.17.1Mark? 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.
Is there a reference I could check for the meaning of the flag? I'll do an online search in the meantime.
Thanks again, ..mark
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