Created attachment 28173 [details] [review]
Patch to initialize parameter being sent to dbind_any_marshal_va

Using the at-spi2-core and at-spi2-atk code from git master, I run the at-spi-registryd in one shell and another application (gcalctool) in another shell.  As soon as I run gcalctool, the at-spi-registryd dumps core.  Here's a debug trace:

(dbx) where
=>[1] dbind_any_marshal_va(iter = 0x8047660, arg_types = 0x8047648, args = 0x80476e4), line 356 in "dbind-any.c"
  [2] dbind_emit_signal_va(cnx = 0x80961e8, path = 0x805bf5c "/org/freedesktop/atspi/registry", interface = 0x805bf7c "org.freedesktop.atspi.Registry", signal = 0x805bf9c "updateApplications", opt_error = (nil), arg_types = 0x69 "<bad address 0x69>", args = 0x80476e4), line 180 in "dbind.c"
  [3] emit(reg = 0x8098320, itf = 0x805bf7c "org.freedesktop.atspi.Registry", name = 0x805bf9c "updateApplications", ftype = 105, ... = 0x80476fc, ...), line 62 in "registry.c"
  [4] add_application(bus = 0x80961e8, reg = 0x8098320, app = 0x809de9c ":1.186"), line 138 in "registry.c"
  [5] impl_registerApplication(bus = 0x80961e8, message = 0x809de20, user_data = 0x8098320), line 196 in "registry.c"
  [6] handle_other(bus = 0x80961e8, message = 0x809de20, path = 0x8095348, iface = 0x809df30 "org.freedesktop.atspi.Registry", member = 0x809df58 "registerApplication", pathstr = 0x809dee0 "/org/freedesktop/atspi/registry"), line 494 in "droute.c"
  [7] handle_message(bus = 0x80961e8, message = 0x809de20, user_data = 0x8095348), line 534 in "droute.c"
  [8] _dbus_object_tree_dispatch_and_unlock(0x808d3b0), at 0xfd4d4fc3 
  [9] dbus_connection_dispatch(0x80961e8), at 0xfd4c7517 
  [10] message_queue_dispatch(0x8095ea0, 0x0, 0x0, 0xfd402714), at 0xfef59f41 
  [11] g_main_context_dispatch(0x80946e8, 0x0, 0x808d578, 0x2), at 0xfd4028da 
  [12] g_main_context_iterate(0x80946e8, 0x1, 0x1, 0x80960b8), at 0xfd402f7d 
  [13] g_main_loop_run(0x808d380, 0x0), at 0xfd4035f1 
  [14] main(argc = 1, argv = 0x8047a98), line 130 in "registry-main.c"

In digging into this, I notice the following:

* at-spi2-core/registryd/registry.c:emit calls dbind_emit_signal_va.  The penultimate parameter is 'ftype', which is an int.

* at-spi2-core/dbind/dbind.c:dbind_emit_signal_va expects a 'const char *arg_types' instead of the int ftype being passed to it.  This is kind of a red herring, though, because arg_types isn't used in this method.

* This same dbind_emit_signal_va method, however, creates an uninitialized 'char *p' that it then sends to at-spi2-core/dbind/dbind-any.c:dbind_any_marshal_va.  dbind_any_marshal_va seems to assume it will be initialized to something, and this seems to be the source of the problem.

The attached patch initializes "*p" to the empty string and seems to solve the crash. I've no idea if this is the right thing to do, though.