Re: with-url

[Dmitry Gutov <dgutov@yandex.ru>]

On 22.01.2017 19:36, Eli Zaretskii wrote:

> With the current implementation of concurrency, threads cannot
> usefully signal anything: if a thread raises a signal that is not
> caught, it simply dies.  And you cannot catch such a signal from
> another thread.

The idea is that it would be caught by the caller in the same thread.

> So your proposal would mean that the thread which runs the async code
> sets some variable, and the application in the main thread then
> signals an error based on that variable's value.  is that what you had
> in mind?

The model would function somehow like this:

We're in a certain thread. Elisp code calls with-url, the internals make 
a request, _suspend the current thread_, and when the request is 
complete, the low-level code updates some variable and resumes the 
thread. After that, the code in that thread checks the result of the 
request, and, depending on it, may signal an error.

If the request can't be sent for some reason, so there's no point in 
suspending the thread, the internals can signal an error right away.

Point is, the errors is signaled in the same thread that made the 
request. And the execution looks synchronous from the point of view of 
the high-level code in that thread.

Not sure how/if that would work if the request is made from the main 
thread. Maybe that kind of code would require a minor rewrite.