more secure definition for lua_concat

lapi.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lapi.c,v 1.128 2001/02/12 15:42:44 roberto Exp roberto $
+** $Id: lapi.c,v 1.129 2001/02/13 16:17:53 roberto Exp roberto $
 ** Lua API
 ** See Copyright Notice in lua.h
 */
@@ -707,14 +707,18 @@ LUA_API int lua_getn (lua_State *L, int index) {
 
 
 LUA_API void lua_concat (lua_State *L, int n) {
-  StkId top;
   LUA_LOCK(L);
-  api_check(L, n >= 2);
   api_checknelems(L, n);
-  top = L->top;
-  luaV_strconc(L, n, top);
-  L->top = top-(n-1);
-  luaC_checkGC(L);
+  if (n >= 2) {
+    luaV_strconc(L, n, L->top);
+    L->top -= (n-1);
+    luaC_checkGC(L);
+  }
+  else if (n == 0) {  /* push null string */
+    setsvalue(L->top, luaS_newlstr(L, NULL, 0));
+    api_incr_top(L);
+  }
+  /* else n == 1; nothing to do */
   LUA_UNLOCK(L);
 }
 

lauxlib.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lauxlib.c,v 1.45 2001/01/25 16:45:36 roberto Exp roberto $
+** $Id: lauxlib.c,v 1.46 2001/02/02 19:02:40 roberto Exp roberto $
 ** Auxiliary functions for building Lua libraries
 ** See Copyright Notice in lua.h
 */
@@ -166,10 +166,8 @@ static void adjuststack (luaL_Buffer *B) {
       }
       else break;
     } while (toget < B->level);
-    if (toget >= 2) {
-      lua_concat(L, toget);
-      B->level = B->level - toget + 1;
-    }
+    lua_concat(L, toget);
+    B->level = B->level - toget + 1;
   }
 }
 
@@ -194,10 +192,7 @@ LUALIB_API void luaL_addstring (luaL_Buffer *B, const char *s) {
 
 LUALIB_API void luaL_pushresult (luaL_Buffer *B) {
   emptybuffer(B);
-  if (B->level == 0)
-    lua_pushlstring(B->L, NULL, 0);
-  else if (B->level > 1)
-    lua_concat(B->L, B->level);
+  lua_concat(B->L, B->level);
   B->level = 1;
 }