Compiling C lib and OCaml exe using it, all using ocamlfind
I'm trying to work out how to use ocamlfind
to compile a C li开发者_运维问答brary and an OCaml executable using that C library.
I put together a set of rather silly example files.
% cat sillystubs.c
#include <stdio.h>
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/alloc.h>
#include <caml/custom.h>
value
caml_silly_silly( value unit )
{
CAMLparam1( unit );
printf( "%s\n", __FILE__ );
CAMLreturn( Val_unit );
}
% cat silly.mli
external silly : unit -> unit = "silly_silly"
% cat foo.ml
open Silly
open String
let _ =
print_string "About to call into silly";
silly ();
print_string "Called into silly"
I believe the following is the way to compile up the library:
% ocamlfind ocamlc -c sillystubs.c
% ar rc libsillystubs.a sillystubs.o
% ocamlfind ocamlc -c silly.mli
% ocamlfind ocamlc -a -o silly.cma -ccopt -L${PWD} -cclib -lsillystubs
Now I don't seem to be able to use the created library though:
% ocamlfind ocamlc -custom -o foo foo.cmo silly.cma
/usr/bin/ld: cannot find -lsillystubs
collect2: ld returned 1 exit status
File "_none_", line 1, characters 0-1:
Error: Error while building custom runtime system
The OCaml tools are somewhat mysterious to me, so any pointers would be most welcome.
ocamlmklib to the rescue. Step by step:
$ ocamlc -verbose -c sillystubs.c
$ ocamlmklib -verbose sillystubs.o silly.mli -o silly
$ ocamlc -verbose silly.cma foo.ml -o foo
File "foo.ml", line 1, characters 0-1:
Error: Error while linking foo.cmo:
The external function `silly_silly' is not available
Oops, you defined caml_silly_silly in sillystubs.c but reference silly_silly in silly.mli (so much silly :) Repairing :
$ cat silly.mli
external silly : unit -> unit = "caml_silly_silly"
$ ocamlmklib -verbose sillystubs.o silly.mli -o silly
$ ocamlc -custom -verbose silly.cma foo.ml -o foo
/usr/bin/ld: cannot find -lsilly
collect2: ld returned 1 exit status
File "foo.ml", line 1, characters 0-1:
Error: Error while building custom runtime system
Still no luck? Add -I.
to find needed libraries.
$ ocamlc -I . -verbose silly.cma foo.ml -o foo.byte
$ ocamlc -I . -verbose -custom silly.cma foo.ml -o foo.byte.custom
$ ocamlopt -I . -verbose silly.cmxa foo.ml -o foo.native
But in "real" setup you indeed want to install silly library with ocamlfind and then running compilation via ocamlfind will put needed command-line options in place and everything works automatically. Starting from scratch the whole procedure looks as follows :
$ ocamlc -verbose -c sillystubs.c
$ ocamlmklib -verbose sillystubs.o silly.mli -o silly
$ cat META
version="0"
description="quite silly"
archive(byte)="silly.cma"
archive(native)="silly.cmxa"
$ ocamlfind install silly META silly.cm* *.mli *.a *.so
Installed /usr/local/lib/ocaml/3.11.2/silly/silly.a
Installed /usr/local/lib/ocaml/3.11.2/silly/libsilly.a
Installed /usr/local/lib/ocaml/3.11.2/silly/silly.mli
Installed /usr/local/lib/ocaml/3.11.2/silly/silly.cmxa
Installed /usr/local/lib/ocaml/3.11.2/silly/silly.cmi
Installed /usr/local/lib/ocaml/3.11.2/silly/silly.cma
Installed /usr/local/lib/ocaml/3.11.2/silly/META
Installed /usr/local/lib/ocaml/3.11.2/stublibs/dllsilly.so
Installed /usr/local/lib/ocaml/3.11.2/stublibs/dllsilly.so.owner
$ rm *.cm* *.a *.so *.o
$ ocamlfind ocamlopt -linkpkg -package silly foo.ml -o foo.native
$ ocamlfind ocamlc -custom -linkpkg -package silly foo.ml -o foo.byte.custom
$ ocamlfind ocamlc -linkpkg -package silly foo.ml -o foo.byte
Native and byte versions are ready. BTW ocamlc -custom
is deprecated.
Mystery unveiled I hope.
The OCaml tools are somewhat mysterious to me,
I think so, too. why don't you use omake? omake makes the build sequences simple. http://omake.metaprl.org/manual/omake-build.html#@fun272
I'm a version behind on OCaml, but it looks like silly.cma
has sillystubs
linked dynamically, so you may need a
-ccopt -L${PWD}
on that last line.
Also, I don't see anything you're doing that calls for the extra power of ocamlfind
—you may as well call ocamlc
directly.
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