corrected comparisons of signed (int) with unsigned (size_t)

lstrlib.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lstrlib.c,v 1.235 2015/10/08 15:53:05 roberto Exp roberto $
+** $Id: lstrlib.c,v 1.236 2015/10/28 17:56:51 roberto Exp roberto $
 ** Standard library for string operations and pattern-matching
 ** See Copyright Notice in lua.h
 */
@@ -1339,11 +1339,11 @@ static int str_pack (lua_State *L) {
       case Kchar: {  /* fixed-size string */
         size_t len;
         const char *s = luaL_checklstring(L, arg, &len);
-        if (size <= len)  /* string larger than (or equal to) needed? */
+        if ((size_t)size <= len)  /* string larger than (or equal to) needed? */
           luaL_addlstring(&b, s, size);  /* truncate string to asked size */
         else {  /* string smaller than needed */
           luaL_addlstring(&b, s, len);  /* add it all */
-          while (len++ < size)  /* pad extra space */
+          while (len++ < (size_t)size)  /* pad extra space */
             luaL_addchar(&b, LUA_PACKPADBYTE);
         }
         break;