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Date: Sun, 11 Jul 2004 11:58:02 -0700 (PDT)
From: Andy Yang <yyu08@yahoo.com>
Subject: Re: [Caml-list] Toplevel crashes when trying to call external functions
To: art yerkes <ayerkes@speakeasy.net>
Cc: caml-list@inria.fr
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Hi, 

Since at this point, I am not concerning much about
codes' portability, so I just assume the program run 
on x86 machines, on which 32 bits pointers are
allowed.I modified code as follows:

value zchaff_InitManager(void)
{
  CAMLparam0();  
  CAMLlocal1(val);
  void* solver = SAT_InitManager();
  val = copy_int32((int)solver);
  cout<<"solver = "<<hex<<solver<<endl;
  CAMLreturn ( val );
}

void zchaff_ReadCnf(value mng, value filename)
{
  CAMLparam2(mng, filename);
  SAT_Manager solver = (void*)Int32_val(mng);
  cout<<"solver = "<<hex <<solver <<endl;
  assert(solver != NULL);  
  char * fn = String_val(filename);  
  cout<<"file = "<<fn <<endl;
  read_cnf(solver, fn);
  CAMLreturn0;
}


Thus I should follows ocaml's Tag rules. However, the
problem still exists. Tracing with gdb, I noticed that
the toplevel still crashes in function obj_tag.
However, I cannot find the obj_tag 's sourcecode in
Ocaml's source. There is only a mapping table in
ocaml_dir/byterun/prims.c, in which obj_tag is one of
the primitives.

Thanks a lot!

Andy

> 
> > Hi, all
> > 
> > I am relatively new to Ocaml. Sorry about the spam
> if
> > this is a trivial problem. I am trying to give
> call
> > some external functions. 
> > 
> > Some codes are as follows:
> > 
> > value zchaff_InitManager(void)
> > {
> >   CAMLparam0();  
> >   void * solver = SAT_InitManager();
> >   value val = alloc(1, Custom_tag);
> >   Int32_val(val) = (int) solver;
> >   CAMLreturn ( val );
> > }
> > 
> > }
> > 
> 
> These may not solve this specific problem but I
> think they are good
> advice:
> 
> First:
> 17.9.2. Custom blocks must be allocated via the
> alloc_custom function.
> (And remember that the custom block size argument is
> in bytes).
> 
> Second:
> Passing 1 as the block size to alloc allocates a
> block with one word
> as a tail (at offset 0), but Data_custom_val
> accesses a value in the
> tail at offset 1.  This is probably the error you're
> looking for.
> 
> Third:
> I don't understand why you're going through
> Int32_val and Val_int32
> to get and set your pointer.  You probably want to
> write a new macro
> that will access the custom area as a pointer-sized
> chunk on every
> architecture.  Assuming pointers to be 32-bits
> really is a bad idea.
> -- 
> Hey, Adam Smith, keep your invisible hands to
> yourself!
> 





		
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