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Casser le typage avec Dynlink #4229

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vicuna opened this issue Mar 14, 2007 · 1 comment

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@vicuna
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commented Mar 14, 2007

Original bug ID: 4229
Reporter: @alainfrisch
Assigned to: @mshinwell
Status: resolved (set by @mshinwell on 2017-06-09T15:18:46Z)
Resolution: duplicate
Priority: normal
Severity: minor
Target version: later
Category: documentation
Tags: patch
Related to: #4231 #4839 #6462 #6950 #6957
Monitored by: @glondu jmeber "Julien Signoles" monate @dbuenzli @Chris00 ertai

Bug description

Dynlink autorise à charger un module déjà présent dans le programme principal ou déjà dynlinké avant (si sa signature est la même). En particulier, cela permet de redéfinir l'implémentation d'un type abstrait et donc de casser le typage. Certes, il faut vraiment le chercher (cf plus bas).

Une solution un peu moche consisterait à empecher de cacher un symbole global.

Dans symtable.ml:

let slot_for_setglobal id =
if Tbl.mem id !global_table.num_tbl then 0xffff
else enter_numtable global_table id

Dans interp.c:

Instruct(SETGLOBAL):
  if (*pc != 0xffff) caml_modify(&Field(caml_global_data, *pc), accu);
  accu = Val_unit;
  pc++;
  Next;

Steps to reproduce

abstract.mli:
type t
val print: t -> unit
val x: t

abstract.ml:
type t = int
let print i = Printf.printf "Abstract %i\n" i
let x = 10

static.ml:
let f = Abstract.print

client.ml:
let () = Static.f Abstract.x

sub/abstract.mli = abstract.ml

sub/abstract.ml:
type t = string
let print i = Printf.printf "Abstract %s\n" i
let x = "foo"

main.ml:let () =
Dynlink.init ();
Dynlink.loadfile "client.cmo"; (* utilise abstract.cmo )
Dynlink.loadfile "sub/abstract.cmo";
Dynlink.loadfile "client.cmo" (
utilise sub/abstract.cmo *)

On compile tout ça...

$ ocamlc -o main dynlink.cma abstract.cmo static.cmo main.cmo
$ ./main
Abstract 10
Abstract 67345600

@vicuna

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commented Jun 9, 2017

Comment author: @mshinwell

This has been fixed by #1063 - please continue any discussion there.

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