On Thu, Apr 23, 2009 at 12:37:14AM -0700, David McClain wrote:
> It's been about 5 years since I faced this situation. I'm trying to link 
> my program against the Thread module. Things go well until I do the 
> ocamlopt compilation, then it aborts the make with the message:
>
> ocamlfind ocamlopt -thread -o sdsp.opt   -package camlp4 -package  
> threads -package unix -I ../src -I /usr/local/lib/ocaml/threads  \
> 	-thread -cclib threads.a  nums.cmxa sdsp.cmxa threads/threads.cmxa   \
> 	 readline.cmx scmMain.cmx
>
> File "_none_", line 1, characters 0-1:
> Error: No implementations provided for the following modules:
>          Thread referenced from ../src/sdsp.cmxa(SdlPrims)
> make[1]: *** [sdsp.opt] Error 2
> make: *** [subdirs] Error 2

The order of the files on the command line matters here.  You need to follow
the order given on the page:

  http://caml.inria.fr/pub/docs/manual-ocaml/manual038.html

(in particular it looks like your sdsp.cmxa needs to come after threads.cmxa).
Does that make it work?

Mark