Re: [Caml-list] Line number for index out of bounds

[Richard Jones <rich@annexia.org>]

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:

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

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

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

Rich.

-- 
Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology - http://merjis.com
Team Notepad - intranets and extranets for business - http://team-notepad.com