Ok so it seems Printexc is not the way to go... Can you make sense out 
of this sentence in catch's documentation then?

"This function is deprecated: the runtime system is now able to print 
uncaught exceptions as precisely as|Printexc.catch|does"

In the toplevel, exceptions are printed in a sensible way, i.e. their 
arguments is printed as far as it can go respecting abstract types:

# type t = A | B;;
# exception Bla of t;;
# raise (Bla A);;
Exception: Bla A.

Also it honors my #install_printer when printing arguments.
If I compile the same code, I get:

Fatal error: exception Exc.Bla(0)

It seems there is a very ad-hoc, type-unaware exception handler in 
compiled code (byterun/printexc.c:caml_format_exception?) that can't be 
changed and I was hoping Printexc would do that for me. It seems not; 
so, no other way to change the global catcher?

Thanks,
     -m

Le 04/13/2012 11:18 AM, Gabriel Scherer a écrit :
> It seems Printexc.register_printer affects the other Printexc.*
> functions, not the way the toplevel itself (or the runtime system more
> generally) handles uncaught exceptions.
>
> # Printexc.register_printer begin function Not_found ->  Some "hello" |
> _ ->  None end;;
> - : unit = ()
> # (fun () ->  raise Not_found) ();;
> Exception: Not_found.
> # Printexc.print (fun () ->  raise Not_found) ();;
> Uncaught exception: hello
> Exception: Not_found.
>
>
> On Fri, Apr 13, 2012 at 11:12 AM, Matthias Puech<puech@cs.unibo.it>  wrote:
>> Hello,
>>
>> Is there a way to change printing of uncaught exceptions in the toplevel and
>> in (native/bytecode, 3.12) compiled code without wrapping the whole code in
>> a try ... with or in Printexc.catch?
>>
>> Printexc.catch's documentation says it is deprecated and that the runtime
>> system should be able to print exceptions the way they were registered with
>> Printexc.register_printer, yet
>>
>> # Printexc.register_printer begin function Not_found ->  Some "hello" | _ ->
>> None end;;
>> # raise Not_found;;
>> Exception: Not_found.
>>
>> (* I would expect it to respond [Exception: hello] *)
>>
>> Do I miss something here?
>> Thanks in advance,
>>     -m
>>
>> --
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>