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Date: Sun, 16 Apr 2000 16:40:44 +0300 (IDT)
From: Ohad Rodeh <orodeh@cs.huji.ac.il>
To: caml-list@inria.fr
Subject: Calling C++ from Caml
Message-ID: <Pine.LNX.4.20_heb2.08.0004161630460.6495-100000@zigzag.cs.huji.ac.il>
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Resent-Date: Mon, 17 Apr 2000 20:52:28 +0200
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Hello,
  I'm trying to use C++ code from within Caml. Currently,
the compiler cannot find the requested functions in the compiled
C++ code. 

  A very simple example fails. I have two files:
dh.ml : ML code
xx.cpp : C++ code

The C++ code contains the function:
	value dhml_Try(value dummy) {
	   return Val_unit;
	}
The ML code calls dhml_Try using:
	external dhml_Try : unit -> unit 
	  = "dhml_Try"

	let _ = 
	   dhml_Try();
	   ()	

The compilation seqeunce is as follows:
	c++ -c -w -I$(CAMLLIB) xx.cpp -o xx.o
	ocamlc -c dh.ml
	ocamlc -cc c++ -custom -o dh  xx.o dh.cmo	
/tmp/ccEPQ4W1.o(.data+0x248): undefined reference to `dhml_Try'

  If I use the gcc compiler with C code, instead of C++, this 
sequence works fine. How can I fix this problem? 

    Thanks,
	Ohad.