Re: GC and stack marking

[Dmitry Antipov]

On 05/21/2014 07:39 PM, Eli Zaretskii wrote:

> Now, I have a question: mark_stack stops examining the stack when it
> gets to its own stack frame.  That is certainly safe, but it sounds
> too conservative: it should stop at the stack frame of
> Fgarbage_collect, I think, because no live Lisp object can appear
> while Fgarbage_collect runs, right?

1) Yes, but you need ABI- and machine-specific tricks to find the stack frame 
boundaries. I.e.
while in mark_stack, there is no easy way to find start and end of 
Fgarbage_collect's stack frame.

2) But see GCC's __builtin_frame_address, 
https://gcc.gnu.org/onlinedocs/gcc/Return-Address.html.

3) But even if 2) works on all platforms we have to support, I don't see a 
reasons to complicate
   GC just to avoid scanning a few tens of bytes of an extra stack frame.

Dmitry