'lua_checkstack' doesn't need to check stack overflow

'luaD_growstack' already checks that. This commit also fixes an
internal bug in 'luaD_growstack': a large 'n' could cause an arithmetic
overflow when computing 'needed'.

1 files changed, 2 insertions, 7 deletions

diff --git a/lapi.c b/lapi.c
index 5ee65792..352a385a 100644
--- a/lapi.c
+++ b/lapi.c
@@ -114,13 +114,8 @@ LUA_API int lua_checkstack (lua_State *L, int n) {
   api_check(L, n >= 0, "negative 'n'");
   if (L->stack_last - L->top > n)  /* stack large enough? */
     res = 1;  /* yes; check is OK */
-  else {  /* no; need to grow stack */
-    int inuse = cast_int(L->top - L->stack) + EXTRA_STACK;
-    if (inuse > LUAI_MAXSTACK - n)  /* can grow without overflow? */
-      res = 0;  /* no */
-    else  /* try to grow stack */
-      res = luaD_growstack(L, n, 0);
-  }
+  else  /* need to grow stack */
+    res = luaD_growstack(L, n, 0);
   if (res && ci->top < L->top + n)
     ci->top = L->top + n;  /* adjust frame top */
   lua_unlock(L);