pbx_lua: Support displaying lua error message if no debug table exists

The lua_error_function assumed that lua's debug table and traceback function
are always accessible, which is not the case. This fixes the error message
'Error in the lua error handler' triggred by switch exec() function.
If this happens lua's error message is shown without traceback.

Change-Id: I34ba0a098f1ae06a3af7b4d1b098bd43f42f96c8

diff --git a/pbx/pbx_lua.c b/pbx/pbx_lua.c
index 741e9507dbd71f02ee7c7d7a2c37c8aaea34d244..8673dfdef5b8a3d9849e93def25bc808c8621769 100644 (file)
--- a/pbx/pbx_lua.c
+++ b/pbx/pbx_lua.c
@@ -805,7 +805,19 @@ static int lua_error_function(lua_State *L)
        lua_pushliteral(L, "\n");
 
        lua_getglobal(L, "debug");
+       if (!lua_istable(L, -1)) {
+               /* Have no 'debug' table for whatever reason */
+               lua_pop(L, 2);
+               /*  Original err message is on stack top now */
+               return 1;
+       }
        lua_getfield(L, -1, "traceback");
+       if (!lua_isfunction(L, -1)) {
+               /* Same here for traceback function */
+               lua_pop(L, 3);
+               /*  Original err message is on stack top now */
+               return 1;
+       }
        lua_remove(L, -2); /* remove the 'debug' table */
 
        lua_pushvalue(L, message_index);