bug#39962: 27.0.90; Crash in Emacs 27.0.90

[Eli Zaretskii <eliz@gnu.org>]

> From: Pieter van Oostrum <pieter-l@vanoostrum.org>
> Cc: 39962@debbugs.gnu.org,  pieter@vanoostrum.org
> Date: Sat, 07 Mar 2020 16:06:09 +0100
> 
> (gdb) f 2
> #2  0x0000000100233af4 in adjust_markers_for_insert (from=36399, 
>     from_byte=36399, to=36401, to_byte=36401, before_markers=false)
>     at insdel.c:294
> 294	      eassert (m->bytepos >= m->charpos
> (gdb) p m
> $1 = (struct Lisp_Marker *) 0x1609db830
> (gdb) p m->bytepos
> $2 = 11538
> (gdb) p m->charpos
> $3 = 0
> (gdb) p Z_BYTE
> No symbol "Z_BYTE" in current context.
> (gdb) p Z
> No symbol "Z" in current context.
> (gdb) p current_buffer->text->z_byte
> No symbol "current_buffer" in current context.
> (gdb) p current_buffer
> No symbol "current_buffer" in current context.
> (gdb) p current_thread->m_current_buffer
> $4 = (struct buffer *) 0x15b29a4b0
> (gdb) p current_thread->m_current_buffer->text->z_byte
> $5 = 529784
> (gdb) p current_thread->m_current_buffer->text->z
> $6 = 529778
> (gdb)

Thanks.  Could it be that the marker in question is from another
buffer?  How does m->buffer compare with
current_thread->m_current_buffer?

> > Also note that this is no longer in GC, at least not directly.
> 
> That's right. Although the cause of this might also have caused the GC problem when the assertion would not have caught it.

Are you saying that GC is somewhere up the call-stack?  If so, can
you show that?