bug#41357: 28.0.50; GC may miss to mark calle safe register content

[Eli Zaretskii]

> From: Andrea Corallo <akrl@sdf.org>
> Cc: bug-gnu-emacs@gnu.org, eggert@cs.ucla.edu
> Date: Sun, 17 May 2020 17:13:26 +0000
> 
> If a C function caller of 'flush_stack_call_func' allocates a
> Lisp_Object in a temp variable and the compiler decide to keep this in a
> callee saved reg while 'flush_stack_call_func' is called this will be
> garbage collected unexpectedly.

Can you show me an example of this (as skeleton C code)?

Thanks.