Allocating caml lists from C : possible bug on amd64

["\"Sayan (Sébastien Li-Thiao-Té)\"" <sayan@crans.org>]

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Hi list,

I am trying to learn how to allocate a list in C and pass the result to 
Caml on an opteron Debian box. Here is the function that I use :

#include <stdio.h>
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/bigarray.h>

value test_liste (value str) {
    // test function to return a list to caml
    value cons;
    cons = caml_alloc_small (2,0);
    caml_modify(&Field(cons,0),Val_int(0));
    caml_modify(&Field(cons,1),Val_int(0));

    printf("This is test_liste.\n");
    printf(String_val(str));
    fflush(stdout);

    if (Is_block(cons)) { printf("true\n");};
    fflush(stdout);
    printf("cons has size %i \n",Wosize_val(cons));
    fflush(stdout);
    return (cons);
}

I call it from (test_liste.ml) :
external test_liste : string -> int list = "test_liste";;
test_liste "oaue";;

Makefile :
         gcc -c -I/usr/lib64/ocaml readPeaks.c
         ocamlc -custom readPeaks.o test_liste.ml -o a.out

The a.out file is compiled without problems but it crashes with a 
segfault. However, if I compile on the same machine in a 32-bit chroot, 
the program works.

Can anyone reproduce this behavior? Is that a bug linked to the 64bit 
implementation of Ocaml or is it a gcc bug?

-- 
Li-Thiao-Té Sébastien

[-- Attachment #2: Makefile --]
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OUTPUT = a.out

all : top
	echo "Make finished."

clean : 
	rm *.cm* *.o $(OUTPUT)
	
top : 
	gcc -c -I/usr/lib64/ocaml readPeaks.c
	ocamlc -custom readPeaks.o test_liste.ml -o $(OUTPUT)


[-- Attachment #3: readPeaks.c --]
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#include <stdio.h>
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/bigarray.h>

value test_liste (value str) {
   // test function to return a list to caml
   value cons;
   cons = caml_alloc_small (2,0);
   caml_modify(&Field(cons,0),Val_int(0));
   caml_modify(&Field(cons,1),Val_int(0));
   
   printf("This is test_liste.\n");
   printf(String_val(str));
   fflush(stdout);

   if (Is_block(cons)) { printf("true\n");};
   fflush(stdout);
   printf("cons has size %i \n",Wosize_val(cons));
   fflush(stdout);
   return (cons);
}

[-- Attachment #4: test_liste.ml --]
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external test_liste : string -> int list = "test_liste";;
test_liste "oaue";;