for some reason, "char **environ" cannot be extern'ed when building a library on Mac OS X. The patch below uses the suggested workaround according to the man page (using _NSGetEnviron()).

--- dbus-sysdeps.c	2008-01-14 20:51:51.000000000 +0100
+++ dbus-sysdeps.c.new	2008-02-22 22:12:34.000000000 +0100
@@ -47,6 +47,11 @@
 #include <errno.h>
 #endif
 
+#ifdef __APPLE__
+/* needed for _NSGetEnviron */
+#include <crt_externs.h>
+#endif
+
 _DBUS_DEFINE_GLOBAL_LOCK (win_fds);
 _DBUS_DEFINE_GLOBAL_LOCK (sid_atom_cache);
 _DBUS_DEFINE_GLOBAL_LOCK (system_users);
@@ -191,7 +196,12 @@
   if (clearenv () != 0)
      rc = FALSE;
 #else
+#ifdef __APPLE__
+/* On Mac OS X, environ can't be accessed directly - use _NSGetEnviron() instead */
+  char **environ = *_NSGetEnviron();
+#else
   extern char **environ;
+#endif
 
   if (environ != NULL)
     environ[0] = NULL;