Making a 64 bit shared library that dynamically links to a 32 bit library on Mac OS X Snow Leopard

Update: After some more reading I see that this problem is totally general, you can't mix architectures in the same process, so 64 bit Java cannot dlopen() a 32 bit library like FMOD. Is there any possible workaround for this, keeping in mind I'm writing my own C interface to the FMOD library?

I need to make a 64-bit dylib on Max OS X because Java Native Access only likes 64-bit libraries on 64-bit machines. The problem is, my C source code dynamically includes FMOD which on Mac only provides 32-bit dylibs. When I try to compile without the -m32 option (since I must output a 64-bit dylib) I get the following error:

    gcc -dynamiclib -std=c99 -pedantic -Wall -O3 -fPIC -pthread -o  ../bin/libpenntotalrecall_fmod.dylib ../../src/libpenntotalrecall_fmod.c -lfmodex -L../../lib/osx/

    ld: warning: in /usr/lib/libfmodex.dylib, missing required architecture x86_64 in file
    Undefined symbols:
      "_FMOD_System_CreateSound", referenced from:
          _startPlayback in ccJnlwrd.o
      "_FMOD_Channel_GetPosition", referenced from:
          _streamPosition in ccJnlwrd.o
      "_FMOD_System_Create", referenced from:
          _startPlayback in ccJnlwrd.o
      "_FMOD_System_PlaySound", referenced from:
          _startPlayback in ccJnlwrd.o
      "_FMOD_Sound_Release", referenced from:
          _stopPlayback in ccJnlwrd.o
      "_FMOD_Channel_IsPlaying", referenced from:
          _playbackInProgress in ccJnlwrd.o
      "_FMOD_System_Update", referenced from:
          _streamPosition in ccJnlwrd.o
          _startPlayback in ccJnlwrd.o
      "_FMOD_Channel_SetPaused", referenced from:
          _startPlayback in ccJnlwrd.o
      "_FMOD_System_Release", ref开发者_StackOverflow社区erenced from:
          _stopPlayback in ccJnlwrd.o
      "_FMOD_System_Init", referenced from:
          _startPlayback in ccJnlwrd.o
      "_FMOD_Channel_SetVolume", referenced from:
          _startPlayback in ccJnlwrd.o
      "_FMOD_System_Close", referenced from:
          _stopPlayback in ccJnlwrd.o
      "_FMOD_Channel_SetCallback", referenced from:
          _startPlayback in ccJnlwrd.o
    ld: symbol(s) not found
    collect2: ld returned 1 exit status
    make: *** [all] Error 1

Shouldn't it be possible to get a 64 bit dylib from my source code that dynamically includes 32 bit libraries?!

As you've noted, you can't mix architectures in the same process.

The workaround is then to have two processes. One of them is a 32 bit "helper" process that links to the 32-bit library and exposes its functions through some IPC mechanism, and the other is the 64-bit Java process linked to your own 64-bit library.

Your 64-bit library starts up the helper process, and provides a set of functions that it implements by passing requests to the helper process over the IPC mechanism and returning the results. The IPC can be as simple as a pair of anonymous pipes created with the pipe() system call.

64-bit binaries cannot link to 32-bit ones or vice-versa. If you can't get the library you want in 32-bit, your best solution is to create a 32-bit proxy program that your main program controls. This is how Safari does Flash in 10.6 — the Flash plugin runs in its own address space.

Just an FYI to anyone who stumbles across this, FMOD's development release contains a 64 bit dylib for Mac OS X. I'm using that now, and I'm sure it will be moved into the main line of the API soon.