Re: master reporting "creating pipe: too many open files"

[Eli Zaretskii]

> From: Stephen Leake <stephen_leake@stephe-leake.org>
> Date: Sat, 16 Jul 2022 09:58:18 -0700
> 
> I have a custom git front-end that works fine in emacs 28, but in
> current emacs master it always reports "creating pipe: too many open
> files" after a commands. Then any subsequent command in emacs that
> requires a file (such as saving a buffer) also fails.
> 
> This is on Windows 8.1, emacs built with mingw64.
> 
> I'm guessing there is some file/process handle that is opened and not
> closed.
> 
> I update my local copy of emacs master rarely, so this change happened
> sometime since Dec 2021; I have not tried to bisect.
> 
> Attached is some simplified code that shows the problem; it runs a
> subprocess the same way the git front-end does. To run, load the file,
> then run M-x dd-test. On my system, master is ok with 10 processes,
> fails with 100 (I did not bisect further). Emacs 28 is ok forever.
> 
> Before I submit a bug report, I want to check that there is nothing
> simple wrong with the code; is it relying on undocumented behaviour in
> emacs 28, or something similar?

You code starts subprocesses in a loop.

Emacs on MS-Windows cannot support more than 30 subprocesses (assuming
no other process objects, like network connection, exist).  That's
because the pselect emulation is limited to 64 handles, and we use 2
handles per subprocess.

Is what you see consistent with this limitation?