Re: Questions about the gc

[Stephen Compall]

"Thiago F.G. Albuquerque" <address@hidden> writes:

> Does [Guile] use a separate stack, or it uses the C stack?

C stack.

> If the latter is the case, how does the gc know which elements of
> the stack are pointers?

It assumes all elements are pointers.

> And, among the pointers, how does is know which ones point to guile
> objects?

Guile knows the pointer ranges it cares about.  These are organized
into areas of memory called "cards".  If a pointer (anything on the
stack between the bottom and current sp, again) points to a cell
location in one of the cards, and the cell is allocated, the cell gets
marked.  Depending on the type of the cell, you may enter recursive
marking.

OT: Other possibilities for GC include reference counting (a pain, as
in Python) and explicit gcproing (as in Emacs).  Neither of these does
nearly as good a job of separating out the GC code from the "normal"
code; in fact, they don't even try.  With mark/sweep, you only need
occasionally scm_remember_upto_here_* in certain special cases.

--
Stephen Compall or s11 or sirian

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