[regression-3.6] Pipe between Cygwin and non Cygwin (CRT/URT) randomly loses characters

Thu Feb 20 16:55:11 GMT 2025

On Feb 20 16:32, Takashi Yano via Cygwin wrote:
> On 2025年2月19日 16:23:41 +0900
> Takashi Yano wrote:
> > On 2025年2月19日 07:59:00 +0100
> > Cedric Blancher wrote:
> > > Good morning!
> > > 
> > > Cygwin 3.6.0-0.374.g4dd859d01c22.x86_64 on Win10/AMD64/64bit:
> > > 
> > > Pipe between Cygwin and non Cygwin (CRT/URT) randomly loses
> > > characters. We do not have a reproducer yet, but it is happening at
> > > least hourly on our test machines. Sometimes we only get a single
> > > character, and sometimes words are missing.
> > > 
> > > Typically it happens like this:
> > > bash -c 'typeset bar="$( powershell -Command ...) ; echo "${bar}""',
> > > where bar does not contain the full output
> > 
> > Please provide full command line that can reproduce your problem.
> > I can not see any pipe in above command.
> > 
> > > Same happens with dash and ksh93.
> > > 
> > > This does not happen between Cygwin processes, i.e. if I compile a
> > > program with UCRT and read from a Cygwin program it fails, and if I
> > > compile the same sources against Cygwin and pipe it into a Cygwin
> > > program it works.
>> I believe this issue is same as:
> https://cygwin.com/pipermail/cygwin/2025-February/257400.html
>> I'm trying to reproduce the issue using the test case attached.
> However, I still cannot.
>> Any additional information?

I concur. I'm running testcases along the lines of
https://cygwin.com/pipermail/cygwin/2025-February/257408.html on two
machines in parallel for hours, and there's not a single failure
in over 100K iterations.
Without a reliable reproduce I won't take another look.
Corinna