Re: [RFC] Adding threads to Eshell

[Jim Porter <jporterbugs@gmail.com>]

On 12/16/2022 11:51 AM, Eli Zaretskii wrote:
>> Date: Thu, 15 Dec 2022 18:37:09 -0800
>> From: Jim Porter <jporterbugs@gmail.com>
>>
>> However, before I go too far, I wanted to check with other, more
>> knowledgeable people: are Emacs threads available on all platforms?
> 
> Yes.  The only known exception is MSDOS.

Ok, so it looks like MSDOS is also the only platform that lacks support 
for async subprocesses. In that case, I think it would be ok to require 
threads for Eshell if you want to execute commands asynchronously.

>> It looks like it requires the pthreads library
> 
> pthreads are required only on Posix platforms; on Windows we use
> Windows-specific APIs instead.  See systhread.c.

Ah ha. I had somehow gotten it into my head that Emacs used pthread 
wrappers on Win32.

> No, they are real threads.  You can see them with any OS-level tool
> that can examine threads.  We just let only a single one of these
> threads to run at any given time (well, with the exception of very
> short time windows).

Oh, ok. I don't think that will make anything harder to implement 
though, so no worries there.

>> I might be able to avoid this issue, but it would be nice to be able
>> to let-bind some defvars and then pass those bindings to an Eshell
>> command to do its thing.
> 
> If that is what you want, you will have to pass those bindings as
> arguments to the thread function.

Like I said in my message to Stefan, I'm not totally sure if this is the 
right way to go, but I want to experiment with it a bit more. It doesn't 
look too hard to pass those bindings in once I have them, but I don't 
know of a good way to get the list of all local bindings of dynamic 
variables in the first place.