Re: Need to get Lisp backtrace when error is in C code

[Robert Weiner <rsw@gnu.org>]

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On Tue, Oct 3, 2017 at 1:50 PM, Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

> > Personally, for errors like this, I would typically include the function
> > name reference so that the location is obvious and users without debug
> > symbols in their Emacs could still report a more useful error.
> > Is this doable?  A good idea?
>
> I think it's desirable, yes.  The problem is how to do it.
>

Even just showing the Lisp backtrace by itself with some note that
the error was raised in C code would narrow down the location tremendously
I think.

​​
> I guess we could try to replace `Ferror` with a C macro that pushes some
> ​​
> caller-info onto the Lisp backtrace before signaling the error (a bit
> ​​
> like we currently push some pseudo-function onto that stack trace
> ​​
> during garbage collection and redisplay).  It won't handle the cases
> ​​
> where we call `Fsignal` instead, nor the cases where we call some
> ​​
> generic C function which then calls Ferror, so to make it really work
> ​​
> well, it'll require more manual work to place the caller-info at the
> ​​
> "right" spot.
>

​A full solution would be a big win.

Bob

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