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Line number for index out of bounds
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Date: 2006-03-06 (11:14)
From: Richard Jones <rich@a...>
Subject: Re: [Caml-list] Line number for index out of bounds
On Mon, Mar 06, 2006 at 11:44:31AM +0100, Andries Hekstra wrote:
> Invalid_argument("index out of bounds")
> Of course, I am very curious in which line number of the program this 
> exception occurs. 
> Is there any way to get hold of this line number?

This is a real problem with OCaml - it's impossible to get stack
traces of where an exception happens with native code.  I'm assuming
you're using native code.  I commonly have cases where a program dies
with "exception: Not_found" because I forgot to enclose some List.find
with an appropriate try ... with clause, or made some wrong
assumption.  Tracking these down is time-consuming.

Possible workarounds:

* Use bytecode, and before running the program set the environment
variable OCAMLRUNPARAM=b which will print a stack trace.

* Surround every possible array index with a try ... with expression
like this:

    (* code which accesses the array *)
    Invalid_argument "index out of bounds" -> assert false

The "assert false" will print the line and character number of the

* Hack ocamlopt to be able to print exceptions properly :-)


Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology -
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