bug#60220: 29.0.60; macOS 13.1 crash shortly after starting Emacs

[Eli Zaretskii]

> From: Aaron Jensen <aaronjensen@gmail.com>
> Date: Tue, 20 Dec 2022 10:59:20 -0500
> Cc: 60220@debbugs.gnu.org
> 
> On Tue, Dec 20, 2022 at 10:40 AM Eli Zaretskii <eliz@gnu.org> wrote:
> >
> > AFAIU, it says that Emacs was _loading_ rng-loc.  That doesn't mean
> > the problem is in rng-loc's code.  The fatal signal comes from the
> > maxOS implementation of dlopen, so I suspect that the way we restart
> > Emacs messes up some OS data structures regarding loaded shared
> > libraries or something.
> >
> > Note that the previous crash you posted also crashes inside dlopen.
> >
> > So I think it's safe to say that restarting Emacs makes loading of
> > *.eln files (and maybe share libraries in general) fragile and tending
> > to crash, for some reason.  Maybe we should explicitly unload all the
> > *.eln files when we restart?
> 
> Interesting. If I restart while launched from lldb, I get the below.
> It happens right away and it doesn't actually restart. This is not the
> behavior I see if I launch it normally or in xcode. I should note that
> occasionally when I restart Emacs it just quits and does not restart.
> I have to restart it manually. Perhaps this is all connected to the
> issue you're suggesting.
> 
> (lldb) process launch
> Process 19414 launched: 'src/emacs' (arm64)
> Process 19414 stopped
> * thread #8, stop reason = exec
>     frame #0: 0x0000000100b2c950 dyld`_dyld_start
> dyld`:
> ->  0x100b2c950 <+0>:  mov    x0, sp
>     0x100b2c954 <+4>:  and    sp, x0, #0xfffffffffffffff0
>     0x100b2c958 <+8>:  mov    x29, #0x0
>     0x100b2c95c <+12>: mov    x30, #0x0
> Target 0: (emacs) stopped.
> (lldb) thread list
> Process 19414 stopped
> * thread #8: tid = 0x3026c, 0x0000000100b2c950 dyld`_dyld_start, stop
> reason = exec
> (lldb) thread backtrace
> * thread #8, stop reason = exec
>   * frame #0: 0x0000000100b2c950 dyld`_dyld_start
> (lldb) continue
> Process 19414 resuming
> Process 19414 exited with status = 14 (0x0000000e) Terminated due to signal 14

What is "signal 14" on macOS?

Anyway, look at the code: we restart by calling execvp.  You or
someone who knowns macOS internals should take a look at what that
means for shared libraries which were loaded by the program that calls
execvp -- what happens with those libraries in the execvp'ed process.
I'm guessing that they are not being unloaded and re-loaded by the new
process, or something to that effect.

Or maybe the way we load the *.eln files causes this, triggered by
'execvp'?

Can you try running for a while Emacs built without native compilation
and restarting it?  That could tell us whether the *.eln files are the
problem.