From 0bdf4d229431dfa241e6fd4d63d144d944f99cfe Mon Sep 17 00:00:00 2001
From: Benoit Giannangeli <giann008@gmail.com>
Date: Fri, 16 Jun 2017 12:19:18 +0200
Subject: str_unpack: pos is size_t in C so -1 should raise initial position
 error

---
 src/lstrlib.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lstrlib.js b/src/lstrlib.js
index a4a5289..7c3fac4 100644
--- a/src/lstrlib.js
+++ b/src/lstrlib.js
@@ -764,7 +764,7 @@ const str_unpack = function(L) {
     let ld = data.length;
     let pos = posrelat(lauxlib.luaL_optinteger(L, 3, 1), ld) - 1;
     let n = 0;  /* number of results */
-    lauxlib.luaL_argcheck(L, pos <= ld, 3, lua.to_luastring("initial position out of string", true));
+    lauxlib.luaL_argcheck(L, pos <= ld && pos >= 0, 3, lua.to_luastring("initial position out of string", true));
     while (fmt.off < fmt.s.length) {
         let details = getdetails(h, pos, fmt);
         let opt = details.opt;
-- 
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