Passing lambda bindings to C for use as callback

Passing lambda bindings to C for use as callback

[Marc Singer]

...works for a while and then the gh_apply fails stating that the
callback function is missing.  My guess is that this callback, an
anonymous lambda binding, is being garbage collected.  

I've found a reference to this problem and some solution being made
for tcl.  Will someone share with me either the solution or a place to
find it?

Thanks.



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Re: Passing lambda bindings to C for use as callback

[Marc Singer]

On Mon, Nov 25, 2002 at 06:45:45PM -0800, Marc Singer wrote:
> ...works for a while and then the gh_apply fails stating that the
> callback function is missing.  My guess is that this callback, an
> anonymous lambda binding, is being garbage collected.  
> 
> I've found a reference to this problem and some solution being made
> for tcl.  Will someone share with me either the solution or a place to
> find it?

I found the answer by browsing an old CVS archive of the guile code.
Turned out to be quite easy.

 1) On startup, I register a hook using scm_c_hook_add () for
    scm_before_sweep_c_hook.

 2) I store SCMs for active callbacks in one datastructure
 
 3) When the hook procedure executes, it calls scm_gc_mark on each of
    the callback SCMs.

Cake.





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Re: Passing lambda bindings to C for use as callback

[Marius Vollmer]

Marc Singer <elf@buici.com> writes:

> I found the answer by browsing an old CVS archive of the guile code.
> Turned out to be quite easy.

You can also pass the SCM objects that you want to protect globally to
the function scm_gc_protect_object.  Guile will then keep the data
structure for you.  You can unprotect such an object with
scm_gc_unprotect_object.  For objects that you wont ever unprotect you
can also use scm_permanent_object.

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Re: Passing lambda bindings to C for use as callback

[Marc Singer]

On Tue, Nov 26, 2002 at 01:10:48PM +0100, Marius Vollmer wrote:
> You can also pass the SCM objects that you want to protect globally to
> the function scm_gc_protect_object.  Guile will then keep the data
> structure for you.  You can unprotect such an object with
> scm_gc_unprotect_object.  For objects that you wont ever unprotect you
> can also use scm_permanent_object.

Was this added after v1.4?


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Re: Passing lambda bindings to C for use as callback

[Thien-Thi Nguyen]

   From: Marc Singer <elf@buici.com>
   Date: Tue, 26 Nov 2002 12:55:56 -0800

   Was this added after v1.4?

for these kind of questions, see:

 http://www.glug.org/snap/api/

where you can find a (dated) per-version scan and a (selectively
elaborated) diff matrix.  patches to improve scan methodology welcome.
(i'm slowly working towards .h scanning for a more complete picture.)

thi


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