Re: GC and stack marking

[Dmitry Antipov]

On 05/21/2014 07:57 PM, Dmitry Antipov wrote:

> 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.

4) mark_stack calls __builtin_unwind_init to save registers onto the stack. So 
if you stop
   at Fgarbage_collect's stack frame, you don't scan the frame of mark_stack 
too and may
   loose Lisp_Objects accessible from registers.

Dmitry