]> On Thu, Oct 30, 2003 at 08:55:48PM +0100, Stefano Zacchiroli wrote: > On Wed, Oct 29, 2003 at 08:39:35PM +0900, Jacques Garrigue wrote: > > I suppose that as Obj.magic is not documented, this is not documented > > either. > > Ok, thanks for your answer. > > Now, let me restate my question: whi obj.magic _and_ "%identity" are not > documented? Usually undocumented stuff is stuff subject to changes, not > stable, ecc ... Obj.magic's "behavior" *is* subject to change, since it depends upon the underlying representation of values. The Obj module's documentation is, in a very real sense, the entire implementation of the O'Caml compiler and runtime. > Practically, a lot of people use Obj.magic when needed and it seems to > be part of the required knowledge to be a "discriminating hacker"(TM). > The reason that it's unsafe and can make your program crash, IMO, is not > a good reason not to have it documented. Indeed C interfacing APIs are > documented and they are as risky as using Obj.magic and friends. It's a little more than just unsafe -- when you use the Obj module, your program becomes dependent upon the implementation of O'Caml. Also, while it's true that interacting with C code is just as unsafe as using the Obj module, interacting with C code is also a lot *harder* than using the Obj module. Presumably, if one understands how to interface O'Caml with C, they're aware of the risks and will exercise sufficient care. Even a seasoned hacker's careless use of Obj.magic can go awry, as seen in the recent thread about IEEE floating point equality. To be fair, David Monniaux posted a message once explaining when Obj.magic is "okay" to use: http://pauillac.inria.fr/caml/caml-list/0975.html Such "okay" uses are sufficiently bizarre, though, that it makes sense to leave the Obj module undocumented -- anyone who needs it will already understand how it works. cheers, William ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners