bug#39962: 27.0.90; Crash in Emacs 27.0.90

[Eli Zaretskii]

> From: Pieter van Oostrum <pieter-l@vanoostrum.org>
> Cc: 39962@debbugs.gnu.org,  pieter@vanoostrum.org
> Date: Sat, 07 Mar 2020 20:14:56 +0100
> 
> #40 0x0000000100314bfe in Ffuncall (nargs=2, args=0x7ffeefbfea18)
>     at eval.c:2796
> 2796      val = funcall_lambda (fun, numargs, args + 1);
> (gdb) p args[0]
> $25 = XIL(0x3960)
> (gdb) xtype
> Lisp_Symbol
> (gdb) xsymbol
> $26 = (struct Lisp_Symbol *) 0x3af8
> Cannot access memory at address 0x3b00
> (gdb) 
> 
> There seems to be something fishy with the Lisp memory.

Indeed.  Are you using the .gdbinit file from the same src directory
where you built Emacs?

The code which produces this crash runs mapatoms, so maybe it somehow
affects the symbols recorded in the obarray?  Can you identify the
Lisp code which is running here?