Original bug ID: 4878
Reporter: kiyoshi
Status: closed (set by @xavierleroy on 2010-04-18T13:02:42Z)
Resolution: not a bug
Priority: normal
Severity: tweak
Version: 3.11.1
Category: ~DO NOT USE (was: OCaml general)
Child of: #4841

Bug description

Cannot make callbacks from C code when using the -output-obj option under Mac OS X (other solution of 0004841)

ocamlopt -output-obj fails as follows:

$ cat a.ml
module A = struct
let inc_ml x = x + 1
end

let _ = Callback.register "A.inc_ml" A.inc_ml

$ cat a_impl.c
#include <stdio.h>
#include <caml/callback.h>

main (int argc, char** argv) {
caml_main(argv);
fprintf(stdout, "%li\n", Long_val(caml_callback_exn(*caml_named_value("A.inc_ml"), Val_long(1))));
fflush(stdout);
return 0;
}

$ cc -c -I /opt/local/lib/ocaml a_impl.c -o a_impl.o
$ ocamlopt -verbose -output-obj -o a.o a.ml

• as -arch x86_64 -o 'a.o' '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlasm26b96d.s'
• as -arch x86_64 -o '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlstartupd0c5bb.o' '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlstartup7ac4c2.s'
• ld -r -o 'a.o' '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlstartupd0c5bb.o' 'a.o' '/opt/local/lib/ocaml/stdlib.a'
  $ cc -o a.out a.o a_impl.o -L/opt/local/lib/ocaml -lasmrun
  Undefined symbols:
  "_caml_apply2", referenced from:
  _caml_callback2_exn in libasmrun.a(amd64.o)
  "_caml_apply3", referenced from:
  _caml_callback3_exn in libasmrun.a(amd64.o)
  ld: symbol(s) not found
  collect2: ld returned 1 exit status
  $ nm -m a.o | grep _caml_apply[23]
  0000000000000100 (__TEXT,__text) non-external _caml_apply2
  00000000000000b0 (__TEXT,__text) non-external _caml_apply3

I know this problem was discussed and resolved in 0004841, but I also know "ld" command with "-keep_private_externs" option works well.
So I propose another way to resolve the problem.
Please refer to a patch attached to this report.
I think that this solution is more simple because ocamlopt can emit ".private_extern" declaration whether "-output-obj" option is specified or not.

A patched ocamlopt works well as follows:?
$ ocamlopt-patched -verbose -output-obj -o a.o a.ml

• as -arch x86_64 -o 'a.o' '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlasmdf8f90.s'
• as -arch x86_64 -o '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlstartup049736.o' '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlstartup56daaa.s'
• ld -r -keep_private_externs -arch x86_64 -o 'a.o' '/var/folders/fy/fyZMID8GGf0SqwDNwWx2XE+++TM/-Tmp-/camlstartup049736.o' 'a.o' '/opt/local/lib/ocaml/stdlib.a'
  $ cc -o a.out a.o a_impl.o -L/opt/local/lib/ocaml -lasmrun
  $ nm -m a.o | grep _caml_apply[23]
  0000000000000100 (__TEXT,__text) private external _caml_apply2
  00000000000000b0 (__TEXT,__text) private external _caml_apply3
  $ ./a.out
  2
  $

Additional information

$ uname -v
Darwin Kernel Version 10.0.0: Fri Jul 31 22:47:34 PDT 2009; root:xnu-1456.1.25~1/RELEASE_I386
$ sw_vers
ProductName: Mac OS X
ProductVersion: 10.6.1
BuildVersion: 10B504
$ port version
Version: 1.8.1
$ port list installed | grep ocaml
ocaml @3.11.1 lang/ocaml
$ cc -verson
i686-apple-darwin10-gcc-4.2.1: no input files
$

File attachments

• patch-configure.diff