From: John Whitington <john@coherentgraphics.co.uk>
To: caml-list@yquem.inria.fr
Subject: Debugging a C / Ocaml interface problem
Date: Thu, 19 Feb 2009 17:18:19 +0000 [thread overview]
Message-ID: <15903958-833F-4698-94AB-DF517CBBCEF2@coherentgraphics.co.uk> (raw)
Hi Folks,
I'm interfacing our Ocaml PDF stuff to C (threads passim), so main
programs in C can use the tools.
Here's a bug which I can't track down. A value somewhere in the (pure)
caml code is changing from one type constructor to another, breaking
the code. So some tag in a block is being trampled on?
I've gone through all the rules in the manual, and can't find anything
wrong.
The minimal broken main C program:
caml_startup(argv);
int hello3 = fromFile("hello.pdf");
removeAttachedFiles(hello3);
char data[] = {1,2,3,4,5,6,7,8,9,0};
setMetadataFromByteArray(hello3, data, 10);
Here are those functions:
int fromFile(char* filename)
{
return(Int_val(caml_callback(*caml_named_value("fromFile"),
caml_copy_string(filename))));
}
void removeAttachedFiles(int pdf)
{
caml_callback(*caml_named_value("removeAttachedFiles"),
Val_int(pdf));
return;
}
void setMetadataFromByteArray(int pdf, char* data, int len)
{
CAMLparam0 ();
CAMLlocal1 (bytestream);
bytestream = alloc_bigarray_dims(BIGARRAY_UINT8 |
BIGARRAY_C_LAYOUT, 1, data, len);
caml_callback2(*caml_named_value("setMetadataFromByteArray"),
Val_int(pdf), bytestream);
CAMLreturn0;
}
And here are the types of the caml functions called by those C
functions:
val fromFile : string -> int
val removeAttachedFiles : int -> unit
val setMetadataFromByteArray : int -> (int,
Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t -> unit
All the functions work ok in other circumstances (i.e not in this
combination).
The failure occurs inside the Caml function setMetadataFromByteArray -
Pdf.Indirect 27 is changing to Pdf.Integer 27 (Pdf.Indirect and
Pdf.Integer are two constructors of the same type).
Can anyone spot anything wrong in the above? Something Bigarray-
related perhaps?
Any suggestions as to how I might go about further debugging this?
With Thanks,
--
John Whitington
Coherent Graphics Ltd
http://www.coherentpdf.com/
next reply other threads:[~2009-02-19 17:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-19 17:18 John Whitington [this message]
2009-02-19 17:34 ` [Caml-list] " Basile STARYNKEVITCH
2009-02-19 17:43 ` John Whitington
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