Bug: luaL_tolstring may get confused with negative index

When object has a '__name' metafield, 'luaL_tolstring' used the
received index after pushing a string on the stack.

1 files changed, 1 insertions, 0 deletions

diff --git a/lauxlib.c b/lauxlib.c
index 94835ef9..8ed1da11 100644
--- a/lauxlib.c
+++ b/lauxlib.c
@@ -881,6 +881,7 @@ LUALIB_API lua_Integer luaL_len (lua_State *L, int idx) {
 
 
 LUALIB_API const char *luaL_tolstring (lua_State *L, int idx, size_t *len) {
+  idx = lua_absindex(L,idx);
   if (luaL_callmeta(L, idx, "__tostring")) {  /* metafield? */
     if (!lua_isstring(L, -1))
       luaL_error(L, "'__tostring' must return a string");