exception error trace back in ocaml

exception error trace back in ocaml

[lin hong]

Hi all,

I have problem getting a full traceback of some exception error. The
traceback looks like this:

Fatal error: exception Invalid_argument("index out of bounds")
Raised at file "camlinternalLazy.ml", line 33, characters 10-11
Called from file "list.ml", line 74, characters 24-34

But that's all I got, both camlinternalLazy.ml and list.ml are ocaml
source code, I still don't know which part of my code trigger it. Also, in
camlinternalLazy.ml line 33, there is a "try .... with e -> raise e", is
this the reason I don't have a full traceback -- Maybe something else
catch the "raise e" ?  Any idea?

Thanks.
Lin

Re: exception error trace back in ocaml

[Sylvain Le Gall]

On 21-06-2010, lin hong <lhong@amnh.org> wrote:
>
> I have problem getting a full traceback of some exception error. The
> traceback looks like this:
>
> Fatal error: exception Invalid_argument("index out of bounds")
> Raised at file "camlinternalLazy.ml", line 33, characters 10-11
> Called from file "list.ml", line 74, characters 24-34
>
> But that's all I got, both camlinternalLazy.ml and list.ml are ocaml
> source code, I still don't know which part of my code trigger it. Also, in
> camlinternalLazy.ml line 33, there is a "try .... with e -> raise e", is
> this the reason I don't have a full traceback -- Maybe something else
> catch the "raise e" ?  Any idea?
>

To get the full trace, you need to compile your code with "-g", i.e.
ocamlc -g foo.ml 

If you don't have this debug flag, you won't see calls from the code you
compiled.

The "try ... with e -> raise e" just re-raise the exception and you will
be able to see it in the full trace.

Regards,
Sylvain Le Gall

Re: [Caml-list] Re: exception error trace back in ocaml

[lin hong]

> On 21-06-2010, lin hong <lhong@amnh.org> wrote:
>>
>> I have problem getting a full traceback of some exception error. The
>> traceback looks like this:
>>
>> Fatal error: exception Invalid_argument("index out of bounds")
>> Raised at file "camlinternalLazy.ml", line 33, characters 10-11
>> Called from file "list.ml", line 74, characters 24-34
>>
>> But that's all I got, both camlinternalLazy.ml and list.ml are ocaml
>> source code, I still don't know which part of my code trigger it. Also,
>> in
>> camlinternalLazy.ml line 33, there is a "try .... with e -> raise e", is
>> this the reason I don't have a full traceback -- Maybe something else
>> catch the "raise e" ?  Any idea?
>>
>
> To get the full trace, you need to compile your code with "-g", i.e.
> ocamlc -g foo.ml
>
> If you don't have this debug flag, you won't see calls from the code you
> compiled.

Thank you for your reply.

I believe the "-g" flag is being used during compile though, for I can get
full traceback with other exception error in the code. This is the first
and only exception error without the full trace.

>
> The "try ... with e -> raise e" just re-raise the exception and you will
> be able to see it in the full trace.
>
> Regards,
> Sylvain Le Gall
>
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Re: [Caml-list] Re: exception error trace back in ocaml

[Eric Cooper]

On 21-06-2010, lin hong <lhong@amnh.org> wrote:
> I have problem getting a full traceback of some exception error. The
> traceback looks like this:
>
> Fatal error: exception Invalid_argument("index out of bounds")
> Raised at file "camlinternalLazy.ml", line 33, characters 10-11
> Called from file "list.ml", line 74, characters 24-34
>
> But that's all I got, both camlinternalLazy.ml and list.ml are ocaml
> source code, I still don't know which part of my code trigger it. Also,
> in
> camlinternalLazy.ml line 33, there is a "try .... with e -> raise e", is
> this the reason I don't have a full traceback -- Maybe something else
> catch the "raise e" ?  Any idea?

That exception was raised when forcing a lazy value (Lazy.force catches
it and re-raises it).  So you'll need to wrap the expression following
the "lazy" keyword with a handler for Invalid_argument, and you might
be able to use Printexc.print_backtrace from there.  But I don't know
why the standard backtrace printer can't "see" into the closure being
forced.

-- 
Eric Cooper             e c c @ c m u . e d u