Subject: bug#74966: 31.0.50; Crash report (using igc on macOS)

From: Pip Cet <[email-masked]>
Date: Thu, 19 Dec 2024 11:48:36 +0000

"Sean Devlin" <[email-masked]> writes:

> Hi folks,

Hello!

> I was using Emacs and encountered a crash.

Thanks for reporting it!

> I am running on macOS, and I built Emacs from scratch/igc using the
> instructions on that branch.
>
> I didn’t have Emacs running under a debugger, but I do have some crash
> information captured by macOS. (See attached.)

I'm not entirely sure this is the actual segfault (the
EXC_BAD_ACCESS/SIGABRT combination is a little odd):

Exception Type:        EXC_BAD_ACCESS (SIGABRT)
Exception Codes:       KERN_INVALID_ADDRESS at 0x595453206f742068 -> 0x000053206f742068 (possible pointer authentication failure)
Exception Codes:       0x0000000000000001, 0x595453206f742068

That's an ASCII string that we treated as a pointer, it seems?

13  apropos-7c1ecbdf-5d074552.eln 	       0x103407010
F6170726f706f732d736166652d646f63756d656e746174696f6e_apropos_safe_documentation_0
+ 208

Is there any way for you to disassemble this function?  At first glance,
there's nothing unusual about it (it does use the symbol function, which
always confuses me when (function x) was intended but #'x was what I
got).

I'm not quite sure where the apropos-7c1ecbdf-5d074552.eln file lives on
macOS, but I think, if you can find, you can run

llvm-objdump -d apropos-7c1ecbdf-5d074552.eln

(which will produce a lot of output; we're interested in the section
belonging to the
F6170726f706f732d736166652d646f63756d656e746174696f6e_apropos_safe_documentation_0
section).

As this is reproducible, it's probably not a stack marking problem.

> At the time, I was trying to use apropos-documentation. I invoked the
> command once, entered a string, and hit RET, and it signaled an error. I
> tried to do this again and Emacs crashed.
>
> I hope this is useful. Please let me know if there’s any other
> information I can collect.

Definitely useful!

Thanks!

Pip