[Caml-list] Interop C-OCaml

[Victor Pereira <vitorm2p@gmail.com>]

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Hello all!

I have some function written in OCaml that I need to call in a C program.

The OCaml function takes a string, performs some computation and also 
outputs a string. Note that these types are not mandatory, just for testing purposes. 

Therefore, I defined a C function like:

char * foo (char * inp) {
  
  CAMLlocal1 (caml_inp) ;
  caml_inp = caml_copy_string (inp);
  
  value * func = caml_named_value (“foo") ;
  
  if (func == NULL)
    puts (“Unable to load OCaml function!") ;

  return strdup(String_val(caml_callback(*func, oinp)));
}

I am able to correctly compile the file with:

ocamlc -c foo.c (according to the manual)

Next, I define the main.c file as:

extern char * foo(char * inp);

int main (int argc, char ** argv)
{

  /* Initialize OCaml code */
  caml_startup(argv);

  /* Do some computation */
  char * inp = “some string";

  printf ("%s\n", foo(inp));
  
  return 0;
}

However, I’m not able to compile the main.c file!
The error output is the following: 

Undefined symbols for architecture x86_64:
  "_caml_startup", referenced from:
      _main in main-05d208.o
  “_foo", referenced from:
      _main in main-05d208.o

I followed the instructions in the manual to interop C and OCaml when
the main program is in the C side.

Nevertheless, If I run the example in the manual, it works very well!

Any idea on what am I doing wrong?

Best,
Vitor



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