Re: MPS GC and its implications

[Eli Zaretskii <eliz@gnu.org>]

> From: Helmut Eller <eller.helmut@gmail.com>
> Cc: gerd.moellmann@gmail.com,  acorallo@gnu.org,  emacs-devel@gnu.org
> Date: Sat, 04 May 2024 06:22:15 +0200
> 
> On Fri, May 03 2024, Eli Zaretskii wrote:
> 
> > Btw, how does one distinguish between these segfaults and "real"
> > segfaults?  When debugging Emacs crashes, being able to do that
> > quickly could mean the difference between an efficient debug session
> > and wasting quite a lot of time on some wild goose chase.
> 
> The .gdbinit sets up a breakpoint in terminate_due_to_signal.  When you
> end up there, then it's "real".  The others are filtered out by MPS.

But that could be too late.  By the time a fatal exception is caught
by a top-level runtime handler and converted to a signal, the context
is lost, and you might not always even know which code caused the
exception, let alone be capable of looking around in the variables
involved in the problem.  At least on MS-Windows this is what happens.
Otherwise, why would we tell GDB to catch SIGSEGV in addition to the
breakpoint in terminate_due_to_signal?

So if the above is the only way, we are going to lose a valuable
debugging aid, I think.