Return value of finished threads

[Michael Albinus <michael.albinus@gmx.de>]

Hi,

these days I'm working on making Tramp thread-safe. This works already,
but is only part of the job.

The other part is *using* threads. My first use case I'll try to
implement is `find-file' with wildcards. That is, for every single file
to be loaded, an own thread is created. A user indicates this
interactively by a prefix argument like "C-u M-x find-file ...".

What I'm missing is a simple possibility to collect the return values of
the respective finished threads (`find-file-noselect' calls), which is a
buffer or a list of buffers. The documentation recommends the use of
global variables, which would be inconvenient for many threads to supervise.

So I'm wondering if we could extend thread support by an indication of
the thread result, when finished. One idea would be that `thread-join'
returns with that value.

Another idea, even broader, would be to extend `condition-notify' by an
argument, which passes a Lisp object to another thread. The
corresponding `condition-wait' would return that value.

What do people think?

Best regards, Michael.