Re: pcall() and coroutine.yield()

[David Given <dg@...>]

Edgar Toernig wrote:
[...]
> Yes, I know them.  Unfortunately, they are not widely available.
> I.e. not on my system and afaik not under Windows either.

I do know they're not available under Cygwin, but they're trivially 
emulateable using some core Windows APIs (Google for 'ucontext windows'). 
However, I'm pretty firmly stuck in the Unix world, and they seem to be pretty 
standard there...

> The major downside I see with the ucontext functions is that they
> perform system calls during swapcontext (to change signal masks).
> Performance goes down the drain...

Okay, I can see that. I haven't really noticed anything, but I'm not doing 
context switches at any great rate.

[...]
> The setup_jmpbuf function I posted earlier is the absolutely
> minimal code[1] required to implement coroutines or userspace
> threads.  I.e. an implementation of the ucontext functions with
> all features required for Lua comes down to this:

I'll remember that, if you don't mind --- it might come in rather handy. 
(Frex, I've just had someone complain that Spey doesn't build under Cygwin. As 
I'm not using signals, this might be just the thing I was looking for...)

--
[insert interesting .sig here]