Re: [Caml-list] Debugging a C / Ocaml interface problem

[Basile STARYNKEVITCH <basile@starynkevitch.net>]

Hello All

John Whitington wrote:
>
>
> int fromFile(char* filename)
> {
>   return(Int_val(caml_callback(*caml_named_value("fromFile"), 
> caml_copy_string(filename))));
> }

You need to follow Ocaml strong garbage collection related rules for 
coding in C.
Are you aware of what a garbage collector is for precisely, how a 
copying GC works, what exactly are local and global roots?
Reading a few paragraphs could help a lot to get a big picture. Please 
read at least 
http://en.wikipedia.org/wiki/Garbage_collection_(computer_science)
Then read again chapter 18 [interfacing C with Ocaml] of the manual 
http://caml.inria.fr/pub/docs/manual-ocaml/manual032.html

The major rule is that every allocated value should be an Ocaml root.

Try coding instead // untested!

int fromFile (char* filename)
{
  CAMLparam0;
  CAMLlocal3(fromfil_v, filnam_v, res_v);
  fromfil_v = *caml_named_value("fromFile");
  filnam_v =  caml_copy_string(filename);
  res_v = caml_callback(fromfil_v, filnam_v);
  CAMLreturnT(int, Int_val(res_v);
}

Hope this helps.

Don't forget that Ocaml (minor) garbage collector is a copying 
generational garbage collector, and read enough material to understand 
what that is meaning.

Regards.


-- 
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
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