cygwin 3.3.x: another problem that may be related to pipes

[Corinna Vinschen]

[Redirected to cygwin-developers]

On Nov 15 17:18, Takashi Yano via Cygwin wrote:
> On Sun, 14 Nov 2021 20:50:59 +0000 (UTC)
> bf wrote:
> > I've a shell script that processes several hundred xz-compressed text files with a pipeline of the form:
> > 
> > find . -depth -type f  ... -print0 | \
> > xargs -0tI @ xzcat -- @ | \
> > iconv --byte-subst='�' --unicode-subst='�' --widechar-subst='�' -f MS-ANSI -t UTF-8 -- | \
> > grep ... \
> > sed ... | \
> > sort ... | \
> > sort ...
> > 
> > . Since updating to cygwin 3.3.x (but not on cygwin 3.2.x) the script consistently fails when decompressing a portion of the files, resulting in lost data, and error messages of the form:
> > 
> > xzcat: (stdout): Write error: Bad address
> 
> Thanks for the report.
> I could reproduce your problem and found the cause.
> 
> raw_read()/raw_write() in fhandler_pipe.cc seems to need handling
> of STATUS_PENDING in nonblocking mode.
> 
> I also confirmed the following patch fixes the issue. However, I
> am not very sure that this is the right thing.
> 
> Corinna, Ken, what do you think?

I'm puzzled.  non-blocking pipes return STATUS_PENDING?  What on earth
is that supposed to mean on non-blocking (as opposed to asynchronous)
pipes?  The problem is that STATUS_PENDING theoretically requires
to wait for... something, the pipe handle, perhaps, and then to check
io.Status.

Is it possible that nonblocking pipes need to be synchronous, i. e.,
setting the FILE_SYNCHRONOUS_IO_NONALERT would fix that?


Thanks,
Corinna