tolua 4.0a: critical bug + patch

[Christian Vogler <cvogler@...>]

The attached patch fixes a bug in tolua 4.0a that can cause bogus
object references to appear. These are to objects on the C stack that
have already been destroyed. Under certain circumstances - when the
C stack patterns are just so - these can cause a VERY difficult to find
and to reproduce crash in the lua GC.

I think it may be better to rewrite the functions in tolua_lb.c to use
the lua API directly, instead of creating tolua bindings for
them. With the new lua API, using tolua pkg files to bind functions
that manipulate the lua stack feels distinctly awkward and is
error-prone, as this bug demonstrates.

- Christian




Index: src/lib/tolua_gp.c
===================================================================
RCS file: /home3/cvogler/src/cvs/3rdParty/tolua/src/lib/tolua_gp.c,v
retrieving revision 1.1.1.1.4.1
diff -u -r1.1.1.1.4.1 tolua_gp.c
--- src/lib/tolua_gp.c  2001/03/06 03:50:09     1.1.1.1.4.1
+++ src/lib/tolua_gp.c  2001/03/11 23:10:33
@@ -40,7 +40,13 @@
 
 int tolua_getvalue (lua_State* L, int narg, int def)
 {
- return lua_gettop(L)<abs(narg) ? def : narg;
+ if (lua_gettop(L)<abs(narg))
+ {
+  lua_pushnil(L);
+  return lua_gettop(L);
+ }
+ else
+  return narg;
 }
 
 int tolua_getbool (lua_State* L, int narg, int def)