Re: [Caml-list] Problem with findlib and threads

[Gerd Stolpmann <info@gerd-stolpmann.de>]

Am 2002.10.14 15:59 schrieb(en) Hans Ole Rafaelsen:
> Hello,
> 
> I'm having trouble linking a library which uses threads, using
> ocamlfind.  The library I'm having trouble with, is the xmlrpc
> library.  (I have added a module which handles xmlrpc requests, and
> this module uses threads.)
> 
> ocamlfind ocamlopt -linkpkg  -package "stew xmlrpc threads" -o server.opt   application_impl.cmx application_skeleton.cmx main_server.cmx
> No implementations provided for the following modules:
>   Thread referenced from /usr/local//lib/ocaml/site-lib/xmlrpc/xmlrpc.cmxa(XmlRPCServer)
> 
> If I remove threads form the package list, I get the same error,

Maybe -thread is missing? Selecting the package "threads" without -thread does
not have any effect.

> ocamlfind ocamlopt -linkpkg  -package "stew xmlrpc" -o server.opt   application_impl.cmx application_skeleton.cmx main_server.cmx
> No implementations provided for the following modules:
> Thread referenced from
> /usr/local//lib/ocaml/site-lib/xmlrpc/xmlrpc.cmxa(XmlRPCServer)
> 
> but removing another package, results in errors related to modules
> defined in that package, and which is what you would expect.
> 
> ocamlfind ocamlopt -linkpkg  -package "xmlrpc threads" -o server.opt   application_impl.cmx application_skeleton.cmx main_server.cmx
> No implementations provided for the following modules:
>   Time referenced from /usr/local//lib/ocaml/site-lib/xmlrpc/xmlrpc.cmxa(XmlRPCServer)
>   Thread referenced from /usr/local//lib/ocaml/site-lib/xmlrpc/xmlrpc.cmxa(XmlRPCServer)
> 
> Thus, it seems that trying to link with the threads library have no
> effect.

As explained.

> 
> I have a similar problem with the byte-code version, but I was able to
> get round the problem by linking in the thread library while linking
> the xmlrpc library.
> 
> ocamlfind ocamlc -cclib '-lstew' -thread -package "xstr threads netclient netstring equeue pxp pcre stew " -a -o xmlrpc.cma \
>         -predicates "" threads.cma xmlRPCTypes.cmo xmlRPCDtd.cmo
> xmlRPCNet.cmo xmlRPCClient.cmo xmlRPCServerMethods.cmo
> xmlRPCServer.cmo
> 
> This is probably not the right way to do this, and trying the same
> approach with the native-code version does not work.
> 
> ocamlfind ocamlopt -cclib '-lstew' -thread -package "xstr threads netclient netstring equeue pxp pcre stew " -a  -o xmlrpc.cmxa \
>         -predicates "" threads.cmxa xmlRPCTypes.cmx xmlRPCDtd.cmx xmlRPCNet.cmx xmlRPCClient.cmx xmlRPCServerMethods.cmx xmlRPCServer.cmx  
> /usr/local//lib/ocaml//threads/threads.cmxa
> is not a compilation unit description.

Linking a library with libraries does not work for native code. Btw, your approach
would also not work if ocaml had been configured for bytecode threads, because the
-thread option has a special effect in this case (selects a different version of the
standard library). This is why ocamlfind demands -thread always, even if the
ocaml compiler sometimes does not need it (when linking executables for POSIX threads).

Simply follow the rule: Give both -thread and -package threads for compiling
and linking.

I hope this helps,

Gerd

------------------------------------------------------------
Gerd Stolpmann * Viktoriastr. 45 * 64293 Darmstadt * Germany 
gerd@gerd-stolpmann.de          http://www.gerd-stolpmann.de
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