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

[Andries Hekstra <andries.hekstra@philips.com>]

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Dear Richard,

Thanks for your email. I indeed use native code as I need the speed. My 
program is 3500 lines, and includes multi-dimensional arrays, to putting 
try's everywhere by hand is out of the question. I would then have to 
write a metaprogram that adds such try commands to an existing OCaml 
program and outputs a longer program with the try's with the asserts. If 
possible I would like to postpone that and try your other option. 

Due to this crashing business I go on a business trip to Asia without any 
ready simulation results for one week.

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

If I would use this week of the trip to try this suggestion you made, how 
will the stack trace give me the line number?

Best regards,

Andries

------------------------------------------------------------------------
Dr. Ir. Andries P. Hekstra
Philips Research 
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Tel./Fax/Secr. +31 40 27 42048/42566/44051 
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Richard Jones <rich@annexia.org> 
06-03-2006 12:14

To
Andries Hekstra/EHV/RESEARCH/PHILIPS@PHILIPS
cc
caml-list@yquem.inria.fr
Subject
Re: [Caml-list] Line number for index out of bounds
Classification







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
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