Re: Asynchronous bug

[Stefan Monnier]

> > From: "Stefan Monnier" <monnier+gnu/emacs/address@hidden>
> > Date: Wed, 30 Apr 2003 14:34:35 -0400
> > 
> > I've been getting random crashes for a while and finally tracked it
> > down to something useful.  The way it manifests itself is typically
> > by a crash in mark_object, most of the time because the value of
> > `nil' is garbage pointing to nowhereland.
> 
> Please show the value of `nil' (in hex) in a normal session and its
> garbled value when this problem happens.

I don't think this is relevant.
The problem is asynchrony.
The backtrace I showed can also be reproduced where the signal
is caught in the middle of pretty much any random piece of code
(other than the BLOCK_INPUT'ed code of course) so meddling with
global variables such as specpdl_ptr is bound to lead to problems.

Another problem I have seen every once in a while is where I get

        Xlib: unexpected async reply (sequence 0x17d6)!

which indicates that we forgot to BLOCK_INPUT around some Xlib calls.

Another way to look at all of this is that our signal handler does
way too many things.  It would be much better to just set a variable
and return immediately.  We could check this variable in QUIT,
for example.


        Stefan