0003760: wish: validation when retrieving public methods

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0003760

OCaml

OCaml general

public

2005-08-16 21:13

2008-01-25 09:37

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administrator

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normal

Severity

feature

Reproducibility

always

Status

closed

Resolution

fixed

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Fixed in Version

3.11+dev

Summary

0003760: wish: validation when retrieving public methods

Description

Full_Name: Nathaniel Gray
Version: 3.08.3
OS: Mac OS X
Submission from: dhcp-133-195.caltech.edu (131.215.133.195)

The C interface to ocaml offers the caml_get_public_method function for
retrieving a closure by hash from an object's method table. Unfortunately, this
function always returns some method, even if the table doesn't contain the
requested method! It seems caml_get_public_method doesn't check that the hash
you supplied matches the hash it found. It would be nice if either: a)
caml_get_public_method verified that it found the correct method and returned
NULL if it didn't, or b) you provided a separate function
caml_get_valid_public_method that does so.

Why would this be useful? For one, it would make misspelling bugs that are
potentially very difficult to find much easier to find. For another, the
ability to query the method table of an object at runtime could prove handy when
interfacing with dynamic languages. For example, I am currently working on an
OCaml <-> Objective-C bridge. Objective-C method dispatch works by searching
the method tables of each class in the inheritance hierarchy up towards the
root. I would like to be able to create an OCamlProxy object that, when it is
asked to respond to a message, looks in the method table of its OCaml object.
If the method is found then it is used, otherwise the message is passed on to
the superclass. I cannot do this with the current implementation, because
there's no way to learn that an object *doesn't* implement a method.

At the very least, this should be considered a documentation bug. It's
important to know what the failure modes of a function are.

Thanks,
-Nathan Gray

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0003761

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Re: [Caml-devel] wish: validation when retrieving public methods (PR#3760)

Notes
(0000270) administrator (administrator) 2005-08-26 14:19	see PR#3761

(0004437) garrigue (manager) 2008-01-25 09:37	It looks like I completely forgot this good idea. This is now done for 3.11: caml_get_public_method returns 0 when the tag was not found. This does not necesseraly mean that the right method was found (hey, even if the name was identical, there is no type information available anyway), but at least this is more elegant than always returning an unrelated method.

Issue History
Date Modified	Username	Field	Change
2005-11-18 10:13	administrator	New Issue
2008-01-22 17:10	doligez	Relationship added	parent of 0003761
2008-01-25 09:37	garrigue	Status	acknowledged => closed
2008-01-25 09:37	garrigue	Note Added: 0004437
2008-01-25 09:37	garrigue	Resolution	open => fixed
2008-01-25 09:37	garrigue	Fixed in Version	=> 3.11+dev