Re: [Emacs-diffs] /srv/bzr/emacs/trunk r101633: Add fd handling with callbacks to select, dbus needs it for async operation.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 27 Sep 2010 08:30:11 +0200
> From: Jan Djärv <jan.h.d@swipnet.se>
> CC: emacs-devel@gnu.org
> 
> This case may be simple, but what does subprocesses (for exampe) mean?  It 
> doesn't mean just "have subprocess", it also means "we can do select" and "we 
> can listen to many inputs at once", and so on.

It means the build supports async subprocesses.  Once upon a time,
several platforms where Emacs could be built did not have this
capability, but nowadays only the DOS build remains without it.

Quite a few of the macros are documented in src/config.in and in
src/m/*.h and src/s/*.h header files.  This one is in config.in.

Btw, `select' is not the problem here, because even the DOS build has
it.  The issue is whether you have `pipe' and `fork'/`exec' (or some
equivalents thereof), and whether `select' can handle network file
descriptors.