From: Goswin von Brederlow <goswin-v-b@web.de>
To: "David Allsopp" <dra-news@metastack.com>
Cc: "'Goswin von Brederlow'" <goswin-v-b@web.de>,
"'Richard Jones'" <rich@annexia.org>, <caml-list@inria.fr>
Subject: Re: [Caml-list] Static exception analysis or alternative to using exceptions
Date: Tue, 08 Jun 2010 11:16:22 +0200 [thread overview]
Message-ID: <87aar5995l.fsf@frosties.localdomain> (raw)
In-Reply-To: <002c01cb00e6$20bfcd30$623f6790$@romulus.metastack.com> (David Allsopp's message of "Mon, 31 May 2010 18:24:28 +0100")
"David Allsopp" <dra-news@metastack.com> writes:
> Goswin von Brederlow wrote:
> <snip>
>> > However if the exception is, say, an I/O error reading a disk file,
>> > these should be thrown, and caught somewhere central where you can
>> > display an error message to the user (for GUI programs) or abort the
>> > current transaction (for server programs). Recovering from such
>> > exceptions properly is still tricky though. Since OCaml lacks
>> > 'finally', you either have to use a 'finally' impl from a library, or
>> > modify your code to not need it (eg. turning calls to 'open_in' and
>> > 'open_out' into a kind of continuation-passing style). Or for small
>> > programs, abort the program and don't deal with recovery at all.
>> >
>> > All in all, this is not ideal for writing correct programs. Some sort
>> > of exception analysis would be most welcome.
>>
>> It would be nice if the possible exceptions of a function would be part of
>> the type. E.g.
>>
>> let f1 () = raise Not_found
>> val f1 : unit -> 'a [ Not_found ]
>>
>> let f2 () = try f1 () with Not_found -> () val f2 : unit -> unit
>>
>> let f3 f = try f () with Not_found -> () val f3: (unit -> 'a [< Not_found
>> | 'B ]) -> 'a [ 'B ]
>>
>> and so on.
>>
>>
>> Someone would have to write a new type system for that though.
>
> Would it be more practical to have that analysis as part of the .annot file?
> Presumably a patch which merged and updated the codebase of ocamlexc to
> produce exception-annotations in that manner might have a chance of making
> it into the OCaml compiler itself. I'm guessing that what you're getting at
> is the ability to see from your code that an exception could escape at any
> given point rather than trying to add Java-style "checked exceptions" to
> OCaml?
>
>
> David
It want it to fail to compile if the interface specifies one set of
exception and the code produces another that is incompatible. The
following should not compile:
module M : sig
val f : int -> int []
end = struct
let h = Hashtbl.create 0
let f x = Hashtbl.find x
end
Since Hashtbl.find can throw Not_found and the function does not catch
that the function still can throw Not_found. This violates the
declaration in the signature that says it never throws an exception.
This goes beyond just annotating what exception can be thrown. It should
do a real validation.
MfG
Goswin
next prev parent reply other threads:[~2010-06-08 9:16 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-26 16:15 Hans Ole Rafaelsen
2010-05-27 9:34 ` [Caml-list] " Alain Frisch
2010-05-27 17:01 ` Richard Jones
2010-05-27 21:13 ` Dario Teixeira
2010-05-31 14:36 ` Goswin von Brederlow
2010-05-31 15:00 ` Florent Ouchet
2010-05-31 17:24 ` David Allsopp
2010-05-31 20:51 ` Török Edwin
2010-06-08 9:16 ` Goswin von Brederlow [this message]
2010-05-31 19:30 ` Nicolas Pouillard
2010-05-31 20:57 ` Lukasz Stafiniak
2010-05-31 21:42 ` blue storm
2010-05-31 19:36 ` Christophe Raffalli
2010-05-26 17:30 Dario Teixeira
2010-05-26 21:10 ` Hans Ole Rafaelsen
2010-05-27 3:37 ` Jacques Le Normand
2010-05-27 8:08 ` Florent Ouchet
2010-05-27 8:50 ` Eray Ozkural
2010-05-27 11:10 ` Florent Ouchet
2010-05-27 8:54 ` David Allsopp
2010-05-27 9:11 ` Mark Shinwell
2010-05-27 9:29 ` David Allsopp
2010-05-27 9:12 ` Daniel Bünzli
2010-05-27 9:19 ` David Allsopp
2010-05-27 9:15 ` David Rajchenbach-Teller
2010-05-27 13:56 ` Hezekiah M. Carty
2010-06-01 19:08 Peter Ronnquist
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