[ocaml-ctypes] Spinning process on osx

[Daniel Bünzli]

Hello, 

I'm getting crazy with a kind of heisen bug that *seems* to occur only with OCaml 4.01.0 but not with 4.00.1.

I have ctypes 0.2.2, libffi 3.0.13, xcode 5 (using clang) on osx 10.8.5.

The bug is quite reproducible in different context with different (UI related) functions, it seems to be sensitive to the length of the function/program. In all the contexts where the bug occurs it eventually spins in obj_addExceptionHandler (see below), unable to get out of that it I try to step the program. 

(gdb) bt
#0 0x00007fff85f18a81 in memmove$VARIANT$sse42 ()
#1 0x00007fff90fd2abc in libunwind::CFI_Parser<libunwind::LocalAddressSpace>::parseInstructions ()
#2 0x00007fff90fd2a5e in libunwind::CFI_Parser<libunwind::LocalAddressSpace>::parseFDEInstructions ()
#3 0x00007fff90fd28db in libunwind::UnwindCursor<libunwind::LocalAddressSpace, libunwind::Registers_x86_64>::getInfoFromDwarfSection ()
#4 0x00007fff90fd0ebd in libunwind::UnwindCursor<libunwind::LocalAddressSpace, libunwind::Registers_x86_64>::setInfoBasedOnIPRegister ()
#5 0x00007fff90fd1555 in libunwind::UnwindCursor<libunwind::LocalAddressSpace, libunwind::Registers_x86_64>::step ()
#6 0x00007fff8ce8c7af in objc_addExceptionHandler ()
#7 0x00007fff87055c6c in _CFDoExceptionOperation ()
#8 0x00007fff8642724c in _NSAppKitLock ()
#9 0x00007fff863e47f7 in NSAccessibilityPostNotificationWithUserInfo ()
#10 0x00007fff865058db in -[NSApplication sendEvent:] ()
#11 0x00000001001f3b84 in Cocoa_PumpEvents ()
#12 0x000000010019ba3e in SDL_PumpEvents ()
#13 0x0000000100172354 in ffi_call_unix64 ()


This is with a program that has the following source, it gets stuck in the call to Sdl.pump_events (). If I try to comment out any part (and dependents) of this program the bug disappears. Especially, if I comment out one of the `video +` in main(), the bug disappears (`+` is `Unsigned.UInt32.logor`). So I suspect some kind of stack alignement issue. 

let test () = 
  match Sdl.create_window "Test" ~w:640 ~h:480 Sdl.Window.resizable with  
  | `Error -> ()
  | `Ok w ->
      Sdl.pump_events ();
      let e = Sdl.Event.create () in
      let s = Sdl.get_event_state Sdl.Event.window_event in
      Printf.printf "Event state: %s" begin match s with 
      | s when s = Sdl.Event.disable -> "disable" 
      | s when s = Sdl.Event.enable -> "enable" 
      | _ -> assert false
      end;
      ignore (Sdl.wait_event_timeout e 1);
      Sdl.destroy_window w;
      ()

let main () = match Sdl.init Sdl.Init.(video + video + events) with 
| `Error -> exit 1
| `Ok -> test (); exit 0

let () = main ()


That's just a first probe if anybody has something obvious in mind. I will provide more info and a fully reproducible test case. But for now I think I'll stick with ocaml 4.00.1 (hoping it's not there but just hiding more deeply) as I need to get some work done. 

Best,

Daniel


P.S. Also I do get the following warnings when I install ctypes

clang: warning: argument unused during compilation: '-fno-defer-pop'
../../../src/ctypes/type_info_stubs.c:134:48: warning: format specifies type 'short' but the argument has type 'int' [-Wformat]
case Short: snprintf(buf, sizeof buf, "%hd", Int_val(v)); break;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
%d
/Users/dbuenzli/.opam/4.01.0/lib/ocaml/caml/mlvalues.h:76:20: note: expanded from macro 'Int_val'
#define Int_val(x) ((int) Long_val(x))
^
/usr/include/secure/_stdio.h:56:62: note: expanded from macro 'snprintf'
__builtin___snprintf_chk (str, len, 0, __darwin_obsz(str), __VA_ARGS__)
^
../../../src/ctypes/type_info_stubs.c:143:53: warning: format specifies type 'char' but the argument has type 'int' [-Wformat]
case Int8_t: snprintf(buf, sizeof buf, "%" PRId8, Int_val(v)); break;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
/Users/dbuenzli/.opam/4.01.0/lib/ocaml/caml/mlvalues.h:76:20: note: expanded from macro 'Int_val'
#define Int_val(x) ((int) Long_val(x))
^
/usr/include/secure/_stdio.h:56:62: note: expanded from macro 'snprintf'
__builtin___snprintf_chk (str, len, 0, __darwin_obsz(str), __VA_ARGS__)
^
../../../src/ctypes/type_info_stubs.c:144:55: warning: format specifies type 'short' but the argument has type 'int' [-Wformat]
case Int16_t: snprintf(buf, sizeof buf, "%" PRId16, Int_val(v)); break;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
/Users/dbuenzli/.opam/4.01.0/lib/ocaml/caml/mlvalues.h:76:20: note: expanded from macro 'Int_val'
#define Int_val(x) ((int) Long_val(x))
^
/usr/include/secure/_stdio.h:56:62: note: expanded from macro 'snprintf'
__builtin___snprintf_chk (str, len, 0, __darwin_obsz(str), __VA_ARGS__)
^
../../../src/ctypes/type_info_stubs.c:146:55: warning: format specifies type 'long long' but the argument has type 'int64' (aka 'long') [-Wformat]
case Int64_t: snprintf(buf, sizeof buf, "%" PRId64, Int64_val(v)); break;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
/Users/dbuenzli/.opam/4.01.0/lib/ocaml/caml/mlvalues.h:268:22: note: expanded from macro 'Int64_val'
#define Int64_val(v) (*((int64 *) Data_custom_val(v)))
^
/usr/include/secure/_stdio.h:56:62: note: expanded from macro 'snprintf'
__builtin___snprintf_chk (str, len, 0, __darwin_obsz(str), __VA_ARGS__)