Subject: Re: bug#51688: ELC+ELN international/emoji.elc crashes

From: Martin Liška <[email-masked]>
Date: Wed, 24 Nov 2021 16:23:53 +0100

On 11/24/21 16:14, Andrea Corallo wrote:
> Eli Zaretskii <[email-masked]> writes:
> 
>>> From: Andreas Schwab <[email-masked]>
>>> Cc: [email-masked],  [email-masked],  [email-masked]
>>> Date: Wed, 24 Nov 2021 14:06:04 +0100
>>>
>>> On Nov 24 2021, Eli Zaretskii wrote:
>>>
>>>> Do you happen to know which libgccjit versions are affected by the
>>>> bug?  We could tell people to avoid them.
>>>
>>> Most likely all of them.
>>
>> Too bad.
>>
>> Andrea, can anything be done to work around this somehow (except to
>> upgrade to a later GCC)?  Or is there nothing we can do except keep
>> fingers crossed?
> 
> I don't think there's much we can do to work around this on Emacs side
> (Martin please correct me if I'm wrong).

No, it's UBSAN in libgccjit library. Unfortunately, the issue is there
for quite a long time and it was exposed by a bad luck where an used
memory was reused (and not initialized) in libgccjit.

Martin

> 
>>>> Or did this bug exist since day one?  (But if it's an old bug, why
>>>> doesn't everyone see these crashes?)
>>>
>>> That's the effect of undefined behaviour.
>>
>> You mean, undefined behavior in libgccjit's own code, right?  Or in
>> our code?
> 
> In libgccjit's own code.
> 
> BR
> 
>    Andrea
>