Shared libraries with ocamlopt callable from C (without main())?

Shared libraries with ocamlopt callable from C (without main())?

[Ben Aurel]

hi
I'm thinking about the possibility to use OCaml as an extension
language. If I wanted to call a OCaml function from langX I had to use
a C wrapper.

    langX -> ( C API of langX | C Wrapper | C API of OCaml ) -> OCaml

Maybe I make it more complicated than it is. But could somebody tell
me if ( and maybe how ) this can be done. I made some attempts, but
there is always a main() function involved. But this C wrapper would
be a shared library.

Thanks in advance
ben

Re: [Caml-list] Shared libraries with ocamlopt callable from C (without main())?

[Matthieu Dubuget]

Ben Aurel a écrit :
> I'm thinking about the possibility to use OCaml as an extension
> language. If I wanted to call a OCaml function from langX I had to use
> a C wrapper.
>
>     langX -> ( C API of langX | C Wrapper | C API of OCaml ) -> OCaml
>   

Yes

> But could somebody tell me if ( and maybe how ) this can be done. I made some attempts, but
> there is always a main() function involved. But this C wrapper would be a shared library.
>   

Exactly. You can deliver your OCaml code as shared library, and then
call it from
any language that can call a shared library.

Could you point out what problem you faced?

Salutations

Matt

RE: [Caml-list] Shared libraries with ocamlopt callable from C(without main())?

[RABIH.ELCHAAR]

The simplest way of achieving what you want might be the following:
1) Write the ocaml code you want to call.
2) register your caml functions via Callback.register
3) In your C code, define the callback values for each ocaml function, via a macro like
#define ACTION(actionname)               \
static value *actionname##_closure = NULL;
and fore each c function that wraps the caml call, call ACTION("camlfunctionname") before your c wrapping code.
4) define an initialization helper (to get the pointers to ocaml functions), something like
#define INITACTION(actionname)                             \
    actionname##_closure = caml_named_value(#actionname);
5) In your DLLMain function, you can have something like
BOOL APIENTRY DllMain(HANDLE module, DWORD reason, void *reserved)
{
  char * argv[2];
  switch (reason) {
  case DLL_PROCESS_ATTACH:
    argv[0] = "--";
    argv[1] = NULL;
    caml_startup(argv);
    INITACTION(analyze)
    INITACTION(updateBlob)
    .....
    break;
  }
  return TRUE;
} 

This handles the C functions:(C Wrapper | C API of OCaml ) -> OCaml defining a C dll with the needed entries.

You can use afterwards your langX -> ( C API of langX -> call above dll).
If your langX can call directly C functions without the need of type conversions, this can do.
If not, this approach might give you two dlls (langX -> C dll) and (C -> ocaml) dll.

If you want only one dll, I think this is only a linking issue, and can be solved by inputing the C->ocaml , compiled ocaml and langX->C together to the linker.

Hope this helps,

Sincerely,
Rabih Chaar

-----Message d'origine-----
De : caml-list-bounces@yquem.inria.fr [mailto:caml-list-bounces@yquem.inria.fr] De la part de Matthieu Dubuget
Envoyé : vendredi 9 janvier 2009 09:22
À : caml-list@inria.fr
Objet : Re: [Caml-list] Shared libraries with ocamlopt callable from C(without main())?

Ben Aurel a écrit :
> I'm thinking about the possibility to use OCaml as an extension
> language. If I wanted to call a OCaml function from langX I had to use
> a C wrapper.
>
>     langX -> ( C API of langX | C Wrapper | C API of OCaml ) -> OCaml
>   

Yes

> But could somebody tell me if ( and maybe how ) this can be done. I made some attempts, but
> there is always a main() function involved. But this C wrapper would be a shared library.
>   

Exactly. You can deliver your OCaml code as shared library, and then
call it from
any language that can call a shared library.

Could you point out what problem you faced?

Salutations

Matt


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Re: [Caml-list] Shared libraries with ocamlopt callable from C (without main())?

[Ben Jakb]

> Could you point out what problem you faced?

I try to create a static library called "libadd5wrapperlib.a" ( I know
kinda WTF ). So here is my simple example:

(Warning: You'll see a lot of bad code below, sorry for that, I work
hard to improve)

=====  $ cat ./add5.ml =====
    (* the code doesnt add anything yet, it just gives 5 back *)
    let add_five () =
      let i = ref 0 in
        i := 5;
        !i;;
    Callback.register "add five" add_five;;


=====  $ cat ./add5wrapperlib.c (Wraps the Ocaml code ) =====
    #include <stdio.h>
    #include <caml/mlvalues.h>
    #include <caml/callback.h>
    int add5wrapper(char **argv) {
        int add_5;
        caml_startup(argv);
        add_5=Int_val(callback(*caml_named_value("add five"),Val_unit));
        return add_5;
}

=====  $ cat ./include/libadd5wrapper.h (header file) =====
    extern int add5 (char **argv);

=====  $ cat ./main.c =====
    #include <stdio.h>
    #include "libadd5wrapper.h"
    int main (int argc,char **argv){
       printf("Gimme - %d \n", add5wrapper());
       return 0;
}

Now I try to BUILD the whole thing:
----------------------------------------------
# 1.) Build the OCaml code
ocamlopt -output-obj add5.ml -o add5-prog.o

# 2.) Create the static library
gcc -c add5wrapperlib.c
ar rs lib/libadd5wrapperlib.a add5wrapperlib.o

# 3.) Create the main object file
gcc -c main.c -Iinclude -I"`ocamlc -where`"

# 4.) Build the whole thing:
gcc --static -Iinclude -Llib -o mainprog.opt main.o add5wrapperlib.o
-L"`ocamlc -where`" -ladd5wrapperlib -lm -ldl -lasmrun

Number 4 is where it breaks. I get a ton of errors and this is where
it ends for me. Because # 4 is also the point where I definitely have
no idea what I'm doing.
Thanks for helping me.

Errors of #4:
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(startup.o): In function
`caml_main':
startup.c:(.text+0x209): undefined reference to `caml_data_segments'
startup.c:(.text+0x21d): undefined reference to `caml_code_segments'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_ceil_float':
floats.c:(.text+0x225): undefined reference to `ceil'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_atan2_float':
floats.c:(.text+0x24b): undefined reference to `atan2'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_atan_float':
floats.c:(.text+0x268): undefined reference to `atan'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_acos_float':
floats.c:(.text+0x285): undefined reference to `acos'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_asin_float':
floats.c:(.text+0x2a2): undefined reference to `asin'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_tanh_float':
floats.c:(.text+0x2bf): undefined reference to `tanh'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_tan_float':
floats.c:(.text+0x2dc): undefined reference to `tan'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_cosh_float':
floats.c:(.text+0x2f9): undefined reference to `cosh'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_cos_float':
floats.c:(.text+0x316): undefined reference to `cos'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_sinh_float':
floats.c:(.text+0x333): undefined reference to `sinh'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_sin_float':
floats.c:(.text+0x350): undefined reference to `sin'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_power_float':
floats.c:(.text+0x376): undefined reference to `pow'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_sqrt_float':
floats.c:(.text+0x3a6): undefined reference to `sqrt'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_log10_float':
floats.c:(.text+0x487): undefined reference to `log10'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_log_float':
floats.c:(.text+0x4a4): undefined reference to `log'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_fmod_float':
floats.c:(.text+0x599): undefined reference to `fmod'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_floor_float':
floats.c:(.text+0x5b6): undefined reference to `floor'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(floats.o): In function
`caml_exp_float':
floats.c:(.text+0x5d3): undefined reference to `exp'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(unix.o): In function
`caml_dlerror':
unix.c:(.text+0x1db): undefined reference to `dlerror'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(unix.o): In function `caml_dlsym':
unix.c:(.text+0x1f5): undefined reference to `dlsym'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(unix.o): In function
`caml_dlclose':
unix.c:(.text+0x208): undefined reference to `dlclose'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(unix.o): In function
`caml_dlopen':
unix.c:(.text+0x223): undefined reference to `dlopen'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(i386.o): In function
`caml_start_program':
(.text+0x129): undefined reference to `caml_program'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(i386.o): In function
`caml_callback2_exn':
(.text+0x221): undefined reference to `caml_apply2'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(i386.o): In function
`caml_callback3_exn':
(.text+0x241): undefined reference to `caml_apply3'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_array_bound_error':
fail.c:(.text+0x75): undefined reference to `caml_exn_Invalid_argument'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_raise_stack_overflow':
fail.c:(.text+0x98): undefined reference to `caml_bucket_Stack_overflow'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_raise_out_of_memory':
fail.c:(.text+0xaa): undefined reference to `caml_bucket_Out_of_memory'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_raise_sys_error':
fail.c:(.text+0x144): undefined reference to `caml_exn_Sys_error'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_invalid_argument':
fail.c:(.text+0x17d): undefined reference to `caml_exn_Invalid_argument'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_failwith':
fail.c:(.text+0x196): undefined reference to `caml_exn_Failure'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_raise_sys_blocked_io':
fail.c:(.text+0x21a): undefined reference to `caml_exn_Sys_blocked_io'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_raise_not_found':
fail.c:(.text+0x22c): undefined reference to `caml_exn_Not_found'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_raise_zero_divide':
fail.c:(.text+0x23e): undefined reference to `caml_exn_Division_by_zero'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(fail.o): In function
`caml_raise_end_of_file':
fail.c:(.text+0x250): undefined reference to `caml_exn_End_of_file'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(roots.o): In function
`caml_init_frame_descriptors':
roots.c:(.text+0x118): undefined reference to `caml_frametable'
roots.c:(.text+0x136): undefined reference to `caml_frametable'
roots.c:(.text+0x18f): undefined reference to `caml_frametable'
roots.c:(.text+0x207): undefined reference to `caml_frametable'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(roots.o): In function
`caml_do_roots':
roots.c:(.text+0x25c): undefined reference to `caml_globals'
roots.c:(.text+0x293): undefined reference to `caml_globals'
/usr/local/godi/lib/ocaml/std-lib/libasmrun.a(roots.o): In function
`caml_oldify_local_roots':
roots.c:(.text+0x364): undefined reference to `caml_globals'
roots.c:(.text+0x36b): undefined reference to `caml_globals'
collect2: ld returned 1 exit status















2009/1/9 Matthieu Dubuget <matthieu.dubuget@gmail.com>:
> Ben Aurel a écrit :
>> I'm thinking about the possibility to use OCaml as an extension
>> language. If I wanted to call a OCaml function from langX I had to use
>> a C wrapper.
>>
>>     langX -> ( C API of langX | C Wrapper | C API of OCaml ) -> OCaml
>>
>
> Yes
>
>> But could somebody tell me if ( and maybe how ) this can be done. I made some attempts, but
>> there is always a main() function involved. But this C wrapper would be a shared library.
>>
>
> Exactly. You can deliver your OCaml code as shared library, and then
> call it from
> any language that can call a shared library.
>
> Could you point out what problem you faced?
>
> Salutations
>
> Matt
>
>
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> Archives: http://caml.inria.fr
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>

Re: [Caml-list] Shared libraries with ocamlopt callable from C (without main())?

[Matthieu Dubuget]

Ben Jakb a écrit :
> I try to create a static library called "libadd5wrapperlib.a" ( I know
> kinda WTF ). So here is my simple example:

I did not succeed (yet ;-) ) in making a static library…
I have an example with a shared one, though.

> 
> (Warning: You'll see a lot of bad code below, sorry for that, I work
> hard to improve)
> 
> =====  $ cat ./add5.ml =====
>     (* the code doesnt add anything yet, it just gives 5 back *)
>     let add_five () =
>       let i = ref 0 in
>         i := 5;
>         !i;;
>     Callback.register "add five" add_five;;

I wrote :

	Callback.register "add five" (fun () -> 5)


> 
> 
> =====  $ cat ./add5wrapperlib.c (Wraps the Ocaml code ) =====
>     #include <stdio.h>
>     #include <caml/mlvalues.h>
>     #include <caml/callback.h>
#include <assert.h>

#define CAMLCBK_INIT( callback, cbk_name) \
        static value *callback = NULL; \
        if (callback == NULL) callback = \
              caml_named_value(cbk_name);\
          assert(callback);

static int init_done = 0;

void init_lib(void){
  char *vide[1];
  vide[0] = NULL;
  if (!init_done){
	caml_startup(vide);
	init_done = 1;
  }
}

int add5wrapper(){
  CAMLCBK_INIT(cbk, "add_five");
  return (Int_val ( caml_callback(*cbk, Val_unit)));
}


> =====  $ cat ./include/libadd5wrapper.h (header file) =====
extern void init_lib(void);
extern int add5wrapper(void);
> 
> =====  $ cat ./main.c =====
>     #include <stdio.h>
>     #include "libadd5wrapper.h"
>     int main (int argc,char **argv){
init_lib();
>        printf("Gimme - %d \n", add5wrapper());
>        return 0;
> }
> 
> Now I try to BUILD the whole thing:
> ----------------------------------------------

ocamlopt -c add5.ml
ocamlopt -c add5wrapperlib.c
ocamlopt -o add5lib.native.so -ccopt -shared add5.cmx add5wrapperlib.o

ocamlc.opt -ccopt -Iinclude -c main.c
gcc -o maintest.native main.o -l:add5lib.native.so -L. -Wl,-rpath=.

In fact, i used ocamlbuild.


--------------myocamlbuild.ml -------------------------------------
open Ocamlbuild_plugin
open Command
open Outcome

(* properties as (string * string) list read from "ocamlc -config" *)
let my_ocamlc_config =
  let rec sc s h =
    Scanf.sscanf s "%s@: %s@\n%n"
      begin fun k v n->
		let h' = (k, v) :: h in
		let len = String.length s in	
		  if
			len - n <= 0
		  then
			h'
		  else
			sc (String.sub s n (len - n)) h'
      end in
    sc (Ocamlbuild_pack.My_unix.run_and_read "ocamlc -config") []

let ext_o = List.assoc "ext_obj" my_ocamlc_config
let ext_so = List.assoc "ext_dll" my_ocamlc_config
let syst = List.assoc "system" my_ocamlc_config

let split s ch =
  let x = ref [] in
  let rec go s =
    let pos = String.index s ch in
      x := (String.before s pos)::!x;
      go (String.after s (pos + 1))
  in
	try
      go s
	with Not_found -> !x

exception Found of string

let pwd () =
  let env = Array.to_list (Unix.environment ()) in
  let rec search = function
	  [] -> ""
	| h :: tl ->
		try
		  Scanf.sscanf h "PWD=%s" (fun x -> x)
		with
			_ -> search tl in
	search env

let split_nl s = split s '\n'

let before_space s =
  try
    String.before s (String.index s ' ')
  with Not_found -> s
	
let uncap_module_path p =
  (Pathname.dirname p) / (String.uncapitalize (Pathname.basename p))

let _ = dispatch begin function
  | After_rules ->
	  if syst = "linux_elf" then
		flag ["link"; "cmldll"]  (S[A"-ccopt";A"-shared"])	
	  else if syst = "mingw" then begin
		flag ["link";"cmldll"] (S[A"-output-obj"])
	  end;

	  flag ["cmldll";"link";"byte"] (S[A"-custom"]);
	  	
	  rule "Mixed C-Ocaml native DLL: cmldll & o* & cmx* -> native DLL
(.dll | .so)"
		~dep:"%.cmldll"
		~prod:("%.native" ^ ext_so)
		begin
		  fun env build ->
			let output = env ("%.native" ^ ext_so)
			and input = env "%.cmldll" in
			let dir = Pathname.dirname input in

			(* TODO: use functions of Pathname module? *)
			let ext_o_files, moduls_files =
			  string_list_of_file input |>
				  List.partition (fun fic -> Filename.check_suffix fic ".o") in
			let objs = ext_o_files |>
				List.map Filename.chop_extension |>
					List.map (fun fic -> fic ^ ext_o) in
			let cmxs = moduls_files |>
				List.map (fun modul ->
							(uncap_module_path modul) -.- "cmx") in
			let deps = cmxs @ objs in

			  List.iter ignore_good
				(build (List.map (fun x -> [dir/x]) deps));

			  Cmd (S [!Options.ocamlopt;
					  A"-o"; Px output;
					  T (tags_of_pathname output++"ocaml"++"native"++"cmldll"++"link");
					  atomize_paths deps
					 ])
		end;

      (* Allows to have .h copied in the _build directory *)
      dep ["file:main.c"] ["include/libadd5wrapper.h"];

	  flag ["include_libadd"] (S[A"-ccopt";A"-Iinclude"]);
	  tag_file "main.c" ["include_libadd"];

	  rule "Compile maintest.native"
		~deps:["main.o"; "add5lib.native.so"]
		~prod:"maintest.native"
		begin fun _ _ ->
		  let target = "maintest.native" in
		  let spc = "-Wl,-rpath=" ^ ((pwd ()) / (!Options.build_dir))  in
			Cmd(
			  S[
				A"gcc";
				A"-o";A target;
				A"main.o";
				A"-l:add5lib.native.so";
				A"-L."; A spc;
			  ])
		end;


  | _ -> ()
end

--------------end of myocamlbuild.ml -----------------------

and the helper file add5lib.mlcdll:

-------------add5lib.mlcdll----------------------
Add5
add5wrapperlib.o
-------------end of add5lib.mlcdll------------------

do
ocamlbuild maintest.native
in order to build.

This myocamlbuild.ml file is a "work in progress".
You can use it as you want if it can be of any help for you.

Salutations

Re: [Caml-list] Shared libraries with ocamlopt callable from C (without main())?

[Ben Jakb]

matthieu,
thanks for the interesting answer.
Unfortunately I can't build 'mycamlbuild.ml', and it is a bit too
advanced for me to understand.

Therefore I'll first go with your standard build commands. So - after
modifing the sources according to your suggestions I run:

BUILD
    ocamlopt -c add5.ml
    ocamlopt -c add5wrapperlib.c
    ocamlopt -o add5lib.native.so -ccopt -shared add5.cmx add5wrapperlib.o
    ocamlc.opt -ccopt -Iinclude -c main.c
    gcc -o maintest.native main.o -l:add5lib.native.so -L. -Wl,-rpath=.

EXECUTION
    cp add5lib.native.so  lib/
    ./maintest.native

ERROR
"maintest.native: add5wrapperlib.c:24: add5wrapper: Assertion `cbk' failed.
Aborted"

This is the referenced line:

    $ sed -n 24p add5wrapperlib.c
CAMLCBK_INIT(cbk, "add_five");


Any ideas what' wrong here?





2009/1/10 Matthieu Dubuget <matthieu.dubuget@gmail.com>:
> Ben Jakb a écrit :
>> I try to create a static library called "libadd5wrapperlib.a" ( I know
>> kinda WTF ). So here is my simple example:
>
> I did not succeed (yet ;-) ) in making a static library…
> I have an example with a shared one, though.
>
>>
>> (Warning: You'll see a lot of bad code below, sorry for that, I work
>> hard to improve)
>>
>> =====  $ cat ./add5.ml =====
>>     (* the code doesnt add anything yet, it just gives 5 back *)
>>     let add_five () =
>>       let i = ref 0 in
>>         i := 5;
>>         !i;;
>>     Callback.register "add five" add_five;;
>
> I wrote :
>
>        Callback.register "add five" (fun () -> 5)
>
>
>>
>>
>> =====  $ cat ./add5wrapperlib.c (Wraps the Ocaml code ) =====
>>     #include <stdio.h>
>>     #include <caml/mlvalues.h>
>>     #include <caml/callback.h>
> #include <assert.h>
>
> #define CAMLCBK_INIT( callback, cbk_name) \
>        static value *callback = NULL; \
>        if (callback == NULL) callback = \
>              caml_named_value(cbk_name);\
>          assert(callback);
>
> static int init_done = 0;
>
> void init_lib(void){
>  char *vide[1];
>  vide[0] = NULL;
>  if (!init_done){
>        caml_startup(vide);
>        init_done = 1;
>  }
> }
>
> int add5wrapper(){
>  CAMLCBK_INIT(cbk, "add_five");
>  return (Int_val ( caml_callback(*cbk, Val_unit)));
> }
>
>
>> =====  $ cat ./include/libadd5wrapper.h (header file) =====
> extern void init_lib(void);
> extern int add5wrapper(void);
>>
>> =====  $ cat ./main.c =====
>>     #include <stdio.h>
>>     #include "libadd5wrapper.h"
>>     int main (int argc,char **argv){
> init_lib();
>>        printf("Gimme - %d \n", add5wrapper());
>>        return 0;
>> }
>>
>> Now I try to BUILD the whole thing:
>> ----------------------------------------------
>
> ocamlopt -c add5.ml
> ocamlopt -c add5wrapperlib.c
> ocamlopt -o add5lib.native.so -ccopt -shared add5.cmx add5wrapperlib.o
>
> ocamlc.opt -ccopt -Iinclude -c main.c
> gcc -o maintest.native main.o -l:add5lib.native.so -L. -Wl,-rpath=.
>
> In fact, i used ocamlbuild.
>
>
> --------------myocamlbuild.ml -------------------------------------
> open Ocamlbuild_plugin
> open Command
> open Outcome
>
> (* properties as (string * string) list read from "ocamlc -config" *)
> let my_ocamlc_config =
>  let rec sc s h =
>    Scanf.sscanf s "%s@: %s@\n%n"
>      begin fun k v n->
>                let h' = (k, v) :: h in
>                let len = String.length s in
>                  if
>                        len - n <= 0
>                  then
>                        h'
>                  else
>                        sc (String.sub s n (len - n)) h'
>      end in
>    sc (Ocamlbuild_pack.My_unix.run_and_read "ocamlc -config") []
>
> let ext_o = List.assoc "ext_obj" my_ocamlc_config
> let ext_so = List.assoc "ext_dll" my_ocamlc_config
> let syst = List.assoc "system" my_ocamlc_config
>
> let split s ch =
>  let x = ref [] in
>  let rec go s =
>    let pos = String.index s ch in
>      x := (String.before s pos)::!x;
>      go (String.after s (pos + 1))
>  in
>        try
>      go s
>        with Not_found -> !x
>
> exception Found of string
>
> let pwd () =
>  let env = Array.to_list (Unix.environment ()) in
>  let rec search = function
>          [] -> ""
>        | h :: tl ->
>                try
>                  Scanf.sscanf h "PWD=%s" (fun x -> x)
>                with
>                        _ -> search tl in
>        search env
>
> let split_nl s = split s '\n'
>
> let before_space s =
>  try
>    String.before s (String.index s ' ')
>  with Not_found -> s
>
> let uncap_module_path p =
>  (Pathname.dirname p) / (String.uncapitalize (Pathname.basename p))
>
> let _ = dispatch begin function
>  | After_rules ->
>          if syst = "linux_elf" then
>                flag ["link"; "cmldll"]  (S[A"-ccopt";A"-shared"])
>          else if syst = "mingw" then begin
>                flag ["link";"cmldll"] (S[A"-output-obj"])
>          end;
>
>          flag ["cmldll";"link";"byte"] (S[A"-custom"]);
>
>          rule "Mixed C-Ocaml native DLL: cmldll & o* & cmx* -> native DLL
> (.dll | .so)"
>                ~dep:"%.cmldll"
>                ~prod:("%.native" ^ ext_so)
>                begin
>                  fun env build ->
>                        let output = env ("%.native" ^ ext_so)
>                        and input = env "%.cmldll" in
>                        let dir = Pathname.dirname input in
>
>                        (* TODO: use functions of Pathname module? *)
>                        let ext_o_files, moduls_files =
>                          string_list_of_file input |>
>                                  List.partition (fun fic -> Filename.check_suffix fic ".o") in
>                        let objs = ext_o_files |>
>                                List.map Filename.chop_extension |>
>                                        List.map (fun fic -> fic ^ ext_o) in
>                        let cmxs = moduls_files |>
>                                List.map (fun modul ->
>                                                        (uncap_module_path modul) -.- "cmx") in
>                        let deps = cmxs @ objs in
>
>                          List.iter ignore_good
>                                (build (List.map (fun x -> [dir/x]) deps));
>
>                          Cmd (S [!Options.ocamlopt;
>                                          A"-o"; Px output;
>                                          T (tags_of_pathname output++"ocaml"++"native"++"cmldll"++"link");
>                                          atomize_paths deps
>                                         ])
>                end;
>
>      (* Allows to have .h copied in the _build directory *)
>      dep ["file:main.c"] ["include/libadd5wrapper.h"];
>
>          flag ["include_libadd"] (S[A"-ccopt";A"-Iinclude"]);
>          tag_file "main.c" ["include_libadd"];
>
>          rule "Compile maintest.native"
>                ~deps:["main.o"; "add5lib.native.so"]
>                ~prod:"maintest.native"
>                begin fun _ _ ->
>                  let target = "maintest.native" in
>                  let spc = "-Wl,-rpath=" ^ ((pwd ()) / (!Options.build_dir))  in
>                        Cmd(
>                          S[
>                                A"gcc";
>                                A"-o";A target;
>                                A"main.o";
>                                A"-l:add5lib.native.so";
>                                A"-L."; A spc;
>                          ])
>                end;
>
>
>  | _ -> ()
> end
>
> --------------end of myocamlbuild.ml -----------------------
>
> and the helper file add5lib.mlcdll:
>
> -------------add5lib.mlcdll----------------------
> Add5
> add5wrapperlib.o
> -------------end of add5lib.mlcdll------------------
>
> do
> ocamlbuild maintest.native
> in order to build.
>
> This myocamlbuild.ml file is a "work in progress".
> You can use it as you want if it can be of any help for you.
>
> Salutations
>

Re: [Caml-list] Shared libraries with ocamlopt callable from C (without main())?

[Matthieu Dubuget]

Ben Jakb a écrit :
> matthieu,
> thanks for the interesting answer.
> Unfortunately I can't build 'mycamlbuild.ml', and it is a bit too
> advanced for me to understand.

If you have a > 3.10 version of ocaml, you don't need to compile
yourself myocamlbuild.ml.

This is done automatically by ocamlbuild.

> 
> Therefore I'll first go with your standard build commands. So - after
> modifing the sources according to your suggestions I run:
> 
> BUILD
>     ocamlopt -c add5.ml
>     ocamlopt -c add5wrapperlib.c
>     ocamlopt -o add5lib.native.so -ccopt -shared add5.cmx add5wrapperlib.o
>     ocamlc.opt -ccopt -Iinclude -c main.c
>     gcc -o maintest.native main.o -l:add5lib.native.so -L. -Wl,-rpath=.
> 
> EXECUTION
>     cp add5lib.native.so  lib/
>     ./maintest.native
> 
> ERROR
> "maintest.native: add5wrapperlib.c:24: add5wrapper: Assertion `cbk' failed.
> Aborted"
> 
> This is the referenced line:
> 
>     $ sed -n 24p add5wrapperlib.c
> CAMLCBK_INIT(cbk, "add_five");
> 
> 
> Any ideas what' wrong here?

Yes ;-)

This is exactly why i use assert there.

I introduced a bug: the string in the C file is "add_five", while the
registered one in the ml file is "add five".


Hope this helps

Re: [Caml-list] Shared libraries with ocamlopt callable from C (without main())?

[Ben Jakb]

> I introduced a bug: the string in the C file is "add_five", while the
> registered one in the ml file is "add five".

Touché. I suppose I looked to long to this code
And yes it works now, thanks ...

2009/1/10 Matthieu Dubuget <matthieu.dubuget@gmail.com>:
> Ben Jakb a écrit :
>> matthieu,
>> thanks for the interesting answer.
>> Unfortunately I can't build 'mycamlbuild.ml', and it is a bit too
>> advanced for me to understand.
>
> If you have a > 3.10 version of ocaml, you don't need to compile
> yourself myocamlbuild.ml.
>
> This is done automatically by ocamlbuild.
>
>>
>> Therefore I'll first go with your standard build commands. So - after
>> modifing the sources according to your suggestions I run:
>>
>> BUILD
>>     ocamlopt -c add5.ml
>>     ocamlopt -c add5wrapperlib.c
>>     ocamlopt -o add5lib.native.so -ccopt -shared add5.cmx add5wrapperlib.o
>>     ocamlc.opt -ccopt -Iinclude -c main.c
>>     gcc -o maintest.native main.o -l:add5lib.native.so -L. -Wl,-rpath=.
>>
>> EXECUTION
>>     cp add5lib.native.so  lib/
>>     ./maintest.native
>>
>> ERROR
>> "maintest.native: add5wrapperlib.c:24: add5wrapper: Assertion `cbk' failed.
>> Aborted"
>>
>> This is the referenced line:
>>
>>     $ sed -n 24p add5wrapperlib.c
>> CAMLCBK_INIT(cbk, "add_five");
>>
>>
>> Any ideas what' wrong here?
>
> Yes ;-)
>
> This is exactly why i use assert there.
>
> I introduced a bug: the string in the C file is "add_five", while the
> registered one in the ml file is "add five".
>
>
> Hope this helps
>

Re: Shared libraries with ocamlopt callable from C (without main())?

[Ben Jakb]

> Can I leech this example to include it in my small ocaml/C wrapping tutorial ?
> http://www.linux-nantes.org/%7Efmonnier/OCaml/ocaml-wrapping-c.php

this would be great (imho). Your articles where the starting point for
my attempts.


2009/1/10 Florent Monnier <monnier.florent@gmail.com>:
> Hi,
> Can I leech this example to include it in my small ocaml/C wrapping tutorial ?
> http://www.linux-nantes.org/%7Efmonnier/OCaml/ocaml-wrapping-c.php
>
> If so, do you want that your name appears or not or you don't mind ?
>
> Cheers
> Florent
> --
> Matthieu Dubuget a écrit :
>> Ben Jakb a écrit :
>> > I try to create a static library called "libadd5wrapperlib.a" ( I know
>> > kinda WTF ). So here is my simple example:
>>
>> I did not succeed (yet ;-) ) in making a static library…
>> I have an example with a shared one, though.
>>
>> > (Warning: You'll see a lot of bad code below, sorry for that, I work
>> > hard to improve)
>> >
>> > =====  $ cat ./add5.ml =====
>> >     (* the code doesnt add anything yet, it just gives 5 back *)
>> >     let add_five () =
>> >       let i = ref 0 in
>> >         i := 5;
>> >         !i;;
>> >     Callback.register "add five" add_five;;
>>
>> I wrote :
>>
>>       Callback.register "add five" (fun () -> 5)
>>
>> > =====  $ cat ./add5wrapperlib.c (Wraps the Ocaml code ) =====
>> >     #include <stdio.h>
>> >     #include <caml/mlvalues.h>
>> >     #include <caml/callback.h>
>>
>> #include <assert.h>
>>
>> #define CAMLCBK_INIT( callback, cbk_name) \
>>         static value *callback = NULL; \
>>         if (callback == NULL) callback = \
>>               caml_named_value(cbk_name);\
>>           assert(callback);
>>
>> static int init_done = 0;
>>
>> void init_lib(void){
>>   char *vide[1];
>>   vide[0] = NULL;
>>   if (!init_done){
>>       caml_startup(vide);
>>       init_done = 1;
>>   }
>> }
>>
>> int add5wrapper(){
>>   CAMLCBK_INIT(cbk, "add_five");
>>   return (Int_val ( caml_callback(*cbk, Val_unit)));
>> }
>>
>> > =====  $ cat ./include/libadd5wrapper.h (header file) =====
>>
>> extern void init_lib(void);
>> extern int add5wrapper(void);
>>
>> > =====  $ cat ./main.c =====
>> >     #include <stdio.h>
>> >     #include "libadd5wrapper.h"
>> >     int main (int argc,char **argv){
>>
>> init_lib();
>>
>> >        printf("Gimme - %d \n", add5wrapper());
>> >        return 0;
>> > }
>> >
>> > Now I try to BUILD the whole thing:
>> > ----------------------------------------------
>>
>> ocamlopt -c add5.ml
>> ocamlopt -c add5wrapperlib.c
>> ocamlopt -o add5lib.native.so -ccopt -shared add5.cmx add5wrapperlib.o
>>
>> ocamlc.opt -ccopt -Iinclude -c main.c
>> gcc -o maintest.native main.o -l:add5lib.native.so -L. -Wl,-rpath=.
>>
>> In fact, i used ocamlbuild.
>>
>>
>> --------------myocamlbuild.ml -------------------------------------
>> open Ocamlbuild_plugin
>> open Command
>> open Outcome
>>
>> (* properties as (string * string) list read from "ocamlc -config" *)
>> let my_ocamlc_config =
>>   let rec sc s h =
>>     Scanf.sscanf s "%s@: %s@\n%n"
>>       begin fun k v n->
>>               let h' = (k, v) :: h in
>>               let len = String.length s in
>>                 if
>>                       len - n <= 0
>>                 then
>>                       h'
>>                 else
>>                       sc (String.sub s n (len - n)) h'
>>       end in
>>     sc (Ocamlbuild_pack.My_unix.run_and_read "ocamlc -config") []
>>
>> let ext_o = List.assoc "ext_obj" my_ocamlc_config
>> let ext_so = List.assoc "ext_dll" my_ocamlc_config
>> let syst = List.assoc "system" my_ocamlc_config
>>
>> let split s ch =
>>   let x = ref [] in
>>   let rec go s =
>>     let pos = String.index s ch in
>>       x := (String.before s pos)::!x;
>>       go (String.after s (pos + 1))
>>   in
>>       try
>>       go s
>>       with Not_found -> !x
>>
>> exception Found of string
>>
>> let pwd () =
>>   let env = Array.to_list (Unix.environment ()) in
>>   let rec search = function
>>         [] -> ""
>>
>>       | h :: tl ->
>>
>>               try
>>                 Scanf.sscanf h "PWD=%s" (fun x -> x)
>>               with
>>                       _ -> search tl in
>>       search env
>>
>> let split_nl s = split s '\n'
>>
>> let before_space s =
>>   try
>>     String.before s (String.index s ' ')
>>   with Not_found -> s
>>
>> let uncap_module_path p =
>>   (Pathname.dirname p) / (String.uncapitalize (Pathname.basename p))
>>
>> let _ = dispatch begin function
>>
>>   | After_rules ->
>>
>>         if syst = "linux_elf" then
>>               flag ["link"; "cmldll"]  (S[A"-ccopt";A"-shared"])
>>         else if syst = "mingw" then begin
>>               flag ["link";"cmldll"] (S[A"-output-obj"])
>>         end;
>>
>>         flag ["cmldll";"link";"byte"] (S[A"-custom"]);
>>
>>         rule "Mixed C-Ocaml native DLL: cmldll & o* & cmx* -> native DLL
>> (.dll | .so)"
>>               ~dep:"%.cmldll"
>>               ~prod:("%.native" ^ ext_so)
>>               begin
>>                 fun env build ->
>>                       let output = env ("%.native" ^ ext_so)
>>                       and input = env "%.cmldll" in
>>                       let dir = Pathname.dirname input in
>>
>>                       (* TODO: use functions of Pathname module? *)
>>                       let ext_o_files, moduls_files =
>>                         string_list_of_file input |>
>>                                 List.partition (fun fic -> Filename.check_suffix fic ".o") in
>>                       let objs = ext_o_files |>
>>                               List.map Filename.chop_extension |>
>>                                       List.map (fun fic -> fic ^ ext_o) in
>>                       let cmxs = moduls_files |>
>>                               List.map (fun modul ->
>>                                                       (uncap_module_path modul) -.- "cmx") in
>>                       let deps = cmxs @ objs in
>>
>>                         List.iter ignore_good
>>                               (build (List.map (fun x -> [dir/x]) deps));
>>
>>                         Cmd (S [!Options.ocamlopt;
>>                                         A"-o"; Px output;
>>                                         T (tags_of_pathname output++"ocaml"++"native"++"cmldll"++"link");
>>                                         atomize_paths deps
>>                                        ])
>>               end;
>>
>>       (* Allows to have .h copied in the _build directory *)
>>       dep ["file:main.c"] ["include/libadd5wrapper.h"];
>>
>>         flag ["include_libadd"] (S[A"-ccopt";A"-Iinclude"]);
>>         tag_file "main.c" ["include_libadd"];
>>
>>         rule "Compile maintest.native"
>>               ~deps:["main.o"; "add5lib.native.so"]
>>               ~prod:"maintest.native"
>>               begin fun _ _ ->
>>                 let target = "maintest.native" in
>>                 let spc = "-Wl,-rpath=" ^ ((pwd ()) / (!Options.build_dir))  in
>>                       Cmd(
>>                         S[
>>                               A"gcc";
>>                               A"-o";A target;
>>                               A"main.o";
>>                               A"-l:add5lib.native.so";
>>                               A"-L."; A spc;
>>                         ])
>>               end;
>>
>>   | _ -> ()
>>
>> end
>>
>> --------------end of myocamlbuild.ml -----------------------
>>
>> and the helper file add5lib.mlcdll:
>>
>> -------------add5lib.mlcdll----------------------
>> Add5
>> add5wrapperlib.o
>> -------------end of add5lib.mlcdll------------------
>>
>> do
>> ocamlbuild maintest.native
>> in order to build.
>>
>> This myocamlbuild.ml file is a "work in progress".
>> You can use it as you want if it can be of any help for you.
>>
>> Salutations
>>
>> _______________________________________________
>> Caml-list mailing list. Subscription management:
>> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
>> Archives: http://caml.inria.fr
>> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
>> Bug reports: http://caml.inria.fr/bin/caml-bugs
>

Re: [Caml-list] Shared libraries with ocamlopt callable from C (without main())?

[Xavier Leroy]

> =====  $ cat ./main.c =====
>     #include <stdio.h>
>     #include "libadd5wrapper.h"
>     int main (int argc,char **argv){
>        printf("Gimme - %d \n", add5wrapper());

Should be add5wrapper(argv) -- as gcc's warnings told you.

>        return 0;
> }
> 
> Now I try to BUILD the whole thing:
> [...]
> Number 4 is where it breaks. I get a ton of errors and this is where
> it ends for me. Because # 4 is also the point where I definitely have
> no idea what I'm doing.

Two things:

- You're not linking in add5-prog.o as far as I can see

- In static mode, the Unix linker is very picky about the relative
  order of -lxxx arguments on the command-line.  For more information,
  see the Info pages for GNU ld.  You probably don't need -static anyway.

The following works:

ocamlopt -output-obj add5.ml -o add5-prog.o
gcc -I`ocamlc -where` -c add5wrapperlib.c
gcc -c main.c
gcc -o mainprog.opt main.o add5wrapperlib.o add5-prog.o \
       -L`ocamlc -where` -lasmrun -ldl -lm

Add "-static" to the last line if you know you really need it.

Hope this puts you back on tracks.

- Xavier Leroy