Re: Intermittent failure with t/003_logical_slots.pl test on windows

Hi,
The same intermittent failure is reproducible on my system.
For the intermittent issues I found that many issues are due to errors
where commands like 'psql -V' are not returning any output.
To reproduce it in an easy way, I wrote a script (.bat file) with
'--version' option for different binaries. And found out that it was
not giving any output for some command (varies for each run).
Then I tried to run the same script after adding 'fflush(stdout)' in
the function called with '--version' option and it started to give
output for each command.
I noticed the same for '--help' option and did the changes for the same.

I have attached the test script(changes the extension to .txt as gmail
is blocking it), output of test before the changes.
I have also attached the patch with changes which resolved the above issue.

This change has resolved most of the intermittent issues for me. I am
facing some more intermittent issues. Will analyse and share it as
well.

Thanks and regards
Shlok Kyal

On Tue, 7 Nov 2023 at 11:05, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> At Mon, 6 Nov 2023 19:42:21 +0530, Nisha Moond <nisha(dot)moond412(at)gmail(dot)com> wrote in
> > > Appending '2>&1 test:
> > > The command still results in NULL and ends up failing as no data is
> > > returned. Which means even no error message is returned. The error log
>
> Thanks for confirmation. So, at least the child process was launced
> successfully in the cmd.exe's view.
>
> Upon a quick check on my end with Windows' _popen, I have obseved the
> following:
>
> - Once a child process is started, it seems to go undetected as an
> error by _popen or subsequent fgets calls if the process ends
> abnormally, with a non-zero exit status or even with a SEGV.
>
> - After the child process has flushed data to stdout, it is possible
> to read from the pipe even if the child process crashes or ends
> thereafter.
>
> - Even if fgets is called before the program starts, it will correctly
> block until the program outputs something. Specifically, when I used
> popen("sleep 5 & target.exe") and immediately performed fgets on the
> pipe, I was able to read the output of target.exe as the first line.
>
> Therefore, based on the information available, it is conceivable that
> the child process was killed by something right after it started, or
> the program terminated on its own without any error messages.
>
> By the way, in the case of aforementioned SEGV, Application Errors
> corresponding to it were identifiable in the Event
> Viewer. Additionally, regarding the exit statuses, they can be
> captured by using a wrapper batch file (.bat) that records
> %ERRORLEVEL% after running the target program. This may yield
> insights, aothough its effectiveness is not guaranteed.
>
> regards.
>
> --
> Kyotaro Horiguchi
> NTT Open Source Software Center
>
>