bug#50339: master creashed in compact_small_strings

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Cc: 50339@debbugs.gnu.org
> Date: Sat, 04 Sep 2021 13:18:28 -0400
> 
> s is nonzero.  It is 0x555556fb4bc0.
> from is 0x5555570edcc0
> 
> Is s supposed to be > from?

No, I think it's supposed to be equal to from.

> from->string is 0.  Strange.

Yes, because s = from->string != 0.

> size is 0x511be45adaa18398
> nbytes is 0x511be45adaa1838d
> 
> That value of size was used to calculate from_end and to_end.

Look like bogus values.

Very strange.

Does anyone have any idea how this could happen?