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[Caml-list] Reference to undefined global using Dynlink module.
-
Dmitri Boulytchev
- Alessandro Baretta
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| Date: | -- (:) |
| From: | Alessandro Baretta <alex@b...> |
| Subject: | Re: [Caml-list] Reference to undefined global using Dynlink module. |
Dmitri Boulytchev wrote:
> Hello everybody,
>
> I didn't get as answer browsing the archive so I decided to ask.
>
> How to avoid "Reference to undefined global ***" error during
> loading *.cmo via Dynlink module?
I had the same problem so I am competent on the subject. I
bet your code looks like the following:
a.ml
***********
open Dynlink
let foo = <whatever>
...
let _ = loadfile "b.cmo"
b.ml
***********
... A.foo ...
^
|
|
Thi is your problem. When you try to access A.foo, module A
has not completed initialization, so it's values appear to
be yet undefined to all other modules.
What you have to do is create a main.ml file which is
initialized last--that is, linked last--where you call the
Dynlink library to load b.ml. Here's how to do it:
a.ml
***************
let foo = <whatever>
b.ml
***************
... A.foo ....
main.ml
***************
open Dynlink
let _ = loadfile "b.cmo"
Makefile
*******************
all : dynlinked_prog b.cmo
b.cmo : b.ml
ocamlc -c b.ml
dynlinked_prog: a.ml main.ml
ocamlc -o $@ a.ml main.ml
# notice the order in which the files are compiled
*******************
When you run make you get an executable and a CMO. When you
run the executable, all the modules that are statically
linked into it are initialized in the order they were
specified in. So first A is initialized (and A.foo is
defined); then, main is initialized (and Dynlink.loadfile is
called). Thus, when loadfile is called, no dynamic linking
error occurs.
Alex
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