bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Michael Albinus]

When a thread has died, `thread-last-error' reports the reason. But
there is no possibility to cleanup this last error, which makes it
inconvenient to check for errors in further threads. A function
`cleanup-thread-last-error' or alike would be helpful.

Or this functionality exist already, and I haven't been able to discover.


In GNU Emacs 27.0.50 (build 13, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-07-14 built on detlef
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bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Date: Mon, 16 Jul 2018 09:18:48 +0200
> 
> 
> When a thread has died, `thread-last-error' reports the reason. But
> there is no possibility to cleanup this last error, which makes it
> inconvenient to check for errors in further threads. A function
> `cleanup-thread-last-error' or alike would be helpful.

How about having thread-last-error clear the error as a side effect,
perhaps when called with an optional argument?

(Btw, I'd rather we made error reporting in non-main threads much more
solid than what we have now.)

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

Hi Eli,

>> When a thread has died, `thread-last-error' reports the reason. But
>> there is no possibility to cleanup this last error, which makes it
>> inconvenient to check for errors in further threads. A function
>> `cleanup-thread-last-error' or alike would be helpful.
>
> How about having thread-last-error clear the error as a side effect,
> perhaps when called with an optional argument?

I'd be happy with either variant.

> (Btw, I'd rather we made error reporting in non-main threads much more
> solid than what we have now.)

While working on making Tramp threadsafe, I use the following instead of
`signal':

(defsubst tramp-compat-signal (error-symbol data)
  "Signal an error to the main thread."
  (when tramp-compat-main-thread
    (tramp-compat-funcall
     'thread-signal tramp-compat-main-thread error-symbol data))
  (signal error-symbol data))

Works sufficient so far. `tramp-compat-main-thread' is a defconst, which
has as value (car (all-threads)). And `tramp-compat-funcall' is a Tramp
internal macro, good for backward compatibility with Emacs 24 and 25.

Best regards, Michael.

PS: Maybe I shall push this to a git branch, giving people a chance for
early tests. `find-file-noselect' survives already in simple cases, w/o
an Emacs crash.

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Cc: 32169@debbugs.gnu.org
> Date: Mon, 16 Jul 2018 16:49:42 +0200
> 
> > How about having thread-last-error clear the error as a side effect,
> > perhaps when called with an optional argument?
> 
> I'd be happy with either variant.

Should be easy to do, I think.

> While working on making Tramp threadsafe, I use the following instead of
> `signal':
> 
> (defsubst tramp-compat-signal (error-symbol data)
>   "Signal an error to the main thread."
>   (when tramp-compat-main-thread
>     (tramp-compat-funcall
>      'thread-signal tramp-compat-main-thread error-symbol data))
>   (signal error-symbol data))
> 
> Works sufficient so far. `tramp-compat-main-thread' is a defconst, which
> has as value (car (all-threads)).

I was certain we had on master a function ti return the main thread,
but I guess I was dreaming.  We could easily add it, though.

In any case, I think it could be a good idea to describe this
technique in the ELisp manual.

> PS: Maybe I shall push this to a git branch, giving people a chance for
> early tests. `find-file-noselect' survives already in simple cases, w/o
> an Emacs crash.

SGTM, thanks.

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

Hi Eli,

>> > How about having thread-last-error clear the error as a side effect,
>> > perhaps when called with an optional argument?
>
> Should be easy to do, I think.

[...]

> I was certain we had on master a function ti return the main thread,
> but I guess I was dreaming.  We could easily add it, though.

Do you want to do it, or shall I? I know, you are overloaded ...

master or emacs-26 branch? I believe threads are not used widely, so we
won't break any code with Emacs 26.

> In any case, I think it could be a good idea to describe this
> technique in the ELisp manual.

Will do, once the changes above have arrived.

>> PS: Maybe I shall push this to a git branch, giving people a chance for
>> early tests. `find-file-noselect' survives already in simple cases, w/o
>> an Emacs crash.
>
> SGTM, thanks.

Later this week. Tomorrow, or on Wednesday, I'll be busy with merging
shadowfile.el.

Best regards, Michael.

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Cc: 32169@debbugs.gnu.org
> Date: Mon, 16 Jul 2018 17:55:31 +0200
> 
> >> > How about having thread-last-error clear the error as a side effect,
> >> > perhaps when called with an optional argument?
> >
> > Should be easy to do, I think.
> 
> [...]
> 
> > I was certain we had on master a function ti return the main thread,
> > but I guess I was dreaming.  We could easily add it, though.
> 
> Do you want to do it, or shall I? I know, you are overloaded ...

Feel free.

> master or emacs-26 branch? I believe threads are not used widely, so we
> won't break any code with Emacs 26.

That's true, but then no one really waits for those new features, so
maybe master after all.

> > In any case, I think it could be a good idea to describe this
> > technique in the ELisp manual.
> 
> Will do, once the changes above have arrived.
> 
> >> PS: Maybe I shall push this to a git branch, giving people a chance for
> >> early tests. `find-file-noselect' survives already in simple cases, w/o
> >> an Emacs crash.
> >
> > SGTM, thanks.
> 
> Later this week. Tomorrow, or on Wednesday, I'll be busy with merging
> shadowfile.el.

Thanks.

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

>> Do you want to do it, or shall I? I know, you are overloaded ...
>
> Feel free.

Will do tomorrow.

>> master or emacs-26 branch? I believe threads are not used widely, so we
>> won't break any code with Emacs 26.
>
> That's true, but then no one really waits for those new features, so
> maybe master after all.

OK. Btw, the changes in Tramp were not intended for Emacs 26. Too heavy.

> Thanks.

Best regards, Michael.

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Michael Albinus]

Version 27.1

Eli Zaretskii <eliz@gnu.org> writes:

>> >> > How about having thread-last-error clear the error as a side effect,
>> >> > perhaps when called with an optional argument?
>> >
>> > Should be easy to do, I think.
>> 
>> [...]
>> 
>> > I was certain we had on master a function ti return the main thread,
>> > but I guess I was dreaming.  We could easily add it, though.
>> 
>> Do you want to do it, or shall I? I know, you are overloaded ...
>
> Feel free.

Done.

Best regards, Michael.

bug#32169: 27.0.50; Wishlist: cleanup of thread-last-error

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Cc: 32169-done@debbugs.gnu.org
> Date: Tue, 17 Jul 2018 12:05:47 +0200
> 
> >> > I was certain we had on master a function ti return the main thread,
> >> > but I guess I was dreaming.  We could easily add it, though.
> >> 
> >> Do you want to do it, or shall I? I know, you are overloaded ...
> >
> > Feel free.
> 
> Done.

Thanks.