Re: Passing C pointers through guile

[ludo@gnu.org (Ludovic Courtès)]

Hi,

"Maciek Godek" <pstrychuj@gmail.com> writes:

> is there any portable and recommended way for passing C pointers around
> in guile environment?
> I think of something like scm_to_ptr (analogous to scm_to_int etc.).
> Certainly such a value would be completely useless for the interpreter.
> One can achieve simillar functionality using the aforementioned
> scm_to_int (keeping track on the word length of the build target),
> but it seems rather unnatural.

If the goal is to make a C object pointed to by some pointer available
to Scheme functions, the recommended (and simplest) way is to use a
"SMOB" (see the manual for details).  In practice, SMOBs incur some
storage overhead because they hold 4 machines words, while you may only
need one.

Another possibility is to use a "uo" field in a struct: it allows you to
have a struct field holding a machine word inaccessible to Scheme
functions (see the "Vtables" node of the manual).

Hope this helps,
Ludovic.