bug#19868: #19868 25.0.50; Compilation eats buffers

[Noam Postavsky]

On Sat, Aug 13, 2016 at 2:44 AM, Eli Zaretskii <eliz@gnu.org> wrote:
>> From: Noam Postavsky <npostavs@users.sourceforge.net>
>> Date: Fri, 12 Aug 2016 16:47:07 -0400
>> Cc: Richard Copley <rcopley@gmail.com>
>>
>> I reproduced this (the hanging, not the buffer eating) on Windows 10,
>> Emacs 25.1, MinGW64.  Stepping with gdb I found the the hang occurs in
>> sys_close where it calls _close (fd).  This is being called from
>> deactivate_process:
>>
>>   for (i = 0; i < PROCESS_OPEN_FDS; i++)
>>     close_process_fd (&p->open_fd[i]); // <-- when i == 2
>
> Does it hang in the _close call itself, or somewhere else?

It's in the _close call itself.

>
> And what is the value of fd?
>
> Can you instrument the relevant code with printf's and see this
> happening without stepping through the code with GDB?  Doing the
> latter might change the timing of the calls, so we might be trying to
> use file descriptors when the process (cmdproxy) is already dead, and
> so the other end of the pipe no longer exists.

I put fprintf+fflush before close_process_fd and around _close:

close_process_fd(-1[i = 0])
close_process_fd(4[i = 1])
going to _close(4)...done _close(4)
close_process_fd(5[i = 2])
going to _close(5)... // here Emacs hangs until I kill bug.exe