Re: [Caml-list] Link a .so/.dll dynamically

[Romain Bardou <bardou@lri.fr>]

Le 14/09/2011 17:09, Benedikt Meurer a écrit :
>
> On Sep 14, 2011, at 17:00 , Romain Bardou wrote:
>
>> My first problem is: I tried something similar for native code (using ocamlopt instead of ocamlc, .cmx instead of .cmo and .cmxa instead of .cma) but ocamlmklib fails with the following error:
>> 	/usr/bin/ld: wrapper.o: relocation R_X86_64_32 against `.rodata' can not be used when making a shared object; recompile with -fPIC
>> 	wrapper.o: could not read symbols: Bad value
>> 	collect2: ld returned 1 exit status
>> I have absolutely no idea what this means, I'm really confused here and Google does not help.
>
> The error messages already includes the answer, you need to pass -fPIC to the C compiler when compiling wrapper.c, i.e.
>
> $ gcc -c -fPIC -o wrapper.o wrapper.c
>
>> Romain Bardou
>
> HTH,
> Benedikt

Thanks for your quick answer.

Actually I tried adding the -fPIC option like this:

	ocamlopt -c -ccopt -fPIC wrapper.c
	ocamlopt -c mylib.ml
	ocamlmklib wrapper.o mylib.cmx -o mylib
	ocamlopt -c main.ml
	ocamlopt dynlink.cmxa main.cmx -o main
	CAML_LD_LIBRARY_PATH=. ./main mylib.cmxa

But when Dynlink.load is called, it fails with the following error:

	error loading shared library: /home/.../mylib.cmxa: invalid ELF header

I'm thinking this is because the .cmxa has not been compiled with the 
-shared option, but I don't know how to tell ocamlmklib to compile with 
the -shared option.

Cheers,

-- 
Romain Bardou