From a585eae6e7ada1ca9271607a4f48dfb17868ab7b Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 27 Jul 2020 12:01:38 -0300
Subject: [PATCH] Fixed bug: Negation overflow in getlocal/setlocal

Adjusted for 5.3

---
diff --git a/src/ldebug.c b/src/ldebug.c
index f1835890..a44e5439 100644
--- a/src/ldebug.c
+++ b/src/ldebug.c
@@ -133,7 +133,7 @@ static const char *upvalname (Proto *p, int uv) {
 
 static const char *findvararg (CallInfo *ci, int n, StkId *pos) {
   int nparams = clLvalue(ci->func)->p->numparams;
-  if (n >= cast_int(ci->u.l.base - ci->func) - nparams)
+  if (n < cast_int(ci->u.l.base - ci->func) - nparams) /* 'n' is negative */
     return NULL;  /* no such vararg */
   else {
     *pos = ci->func + nparams + n;
@@ -148,7 +148,7 @@ static const char *findlocal (lua_State *L, CallInfo *ci, int n,
   StkId base;
   if (isLua(ci)) {
     if (n < 0)  /* access to vararg values? */
-      return findvararg(ci, -n, pos);
+      return findvararg(ci, n, pos);
     else {
       base = ci->u.l.base;
       name = luaF_getlocalname(ci_func(ci)->p, n, currentpc(ci));