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Static exception analysis or alternative to using exceptions
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Date: -- (:)
From: David Allsopp <dra-news@m...>
Subject: RE: [Caml-list] Static exception analysis or alternative to using exceptions
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