[Caml-list] Warning 31: files b.cma(Str) and a.cma(Str) both define a module named Str

[Vu Ngoc San <san.vu-ngoc@laposte.net>]

Hello list

I have a basic compilation question:
I want to write two independent libraries, say A an B, and both use a 
third library, eg. Str

When I write a program which uses A and B, I get
File "b.cma(Str)", line 1:
Warning 31: files b.cma(Str) and a.cma(Str) both define a module named Str

How to get rid of this warning ? Am I doing something wrong ?

Thanks
San

----

Here is a minimal example:

(* This is a.ml *)

let version = "A";;
let _ = print_endline (Str.string_before "Loading the A library -- foo" 
22);;

(* This is b.ml *)

let version = "B";;
let _ =  print_endline (Str.string_before ("Loading the " ^ version ^" 
library -- bar") 23);;

# this is Makefile.a

SOURCES = a.ml
LIBS = str
RESULT = a
all: byte-code-library
-include OCamlMakefile

# this is Makefile.b

SOURCES = b.ml
LIBS = str
RESULT = b
all: byte-code-library
-include OCamlMakefile

(* this is test.ml *)

let _ = print_endline (Str.string_before ("Hello " ^ A.version ^ " and " 
^ B.version ^"---")  13);;

# this is Makefile.test

SOURCES = test.ml
LIBS = a b
RESULT = test
all: byte-code
-include OCamlMakefile