3 files changed, 12 insertions, 6 deletions

diff --git a/src/lapi.js b/src/lapi.js
index 79c666c..ca5a8a0 100644
--- a/src/lapi.js
+++ b/src/lapi.js
@@ -94,7 +94,7 @@ const lua_checkstack = function(L, n) {
     let res;
     let ci = L.ci;
     assert(n >= 0, "negative 'n'");
-    if (L.stack.length - L.top > n) /* stack large enough? */
+    if (L.stack_last - L.top > n) /* stack large enough? */
         res = true;
     else { /* no; need to grow stack */
         let inuse = L.top + lstate.EXTRA_STACK;
@@ -152,6 +152,7 @@ const lua_pushvalue = function(L, idx) {
 const lua_settop = function(L, idx) {
     let func = L.ci.funcOff;
     if (idx >= 0) {
+        assert(idx <= L.stack_last - (func + 1), "new top too large");
         while (L.top < func + 1 + idx)
             L.stack[L.top++] = new TValue(CT.LUA_TNIL, null);
         L.top = func + 1 + idx;
diff --git a/src/ldo.js b/src/ldo.js
index 10be56a..7154a7f 100644
--- a/src/ldo.js
+++ b/src/ldo.js
@@ -43,6 +43,7 @@ const ERRORSTACKSIZE = luaconf.LUAI_MAXSTACK + 200;
 
 const luaD_reallocstack = function(L, newsize) {
     L.stack.length = newsize;
+    L.stack_last = newsize - lstate.EXTRA_STACK;
 };
 
 const luaD_growstack = function(L, n) {
@@ -64,7 +65,7 @@ const luaD_growstack = function(L, n) {
 };
 
 const luaD_checkstack = function(L, n) {
-    if (L.stack.length - L.top <= n)
+    if (L.stack_last - L.top <= n)
         luaD_growstack(L, n);
 };
 
@@ -73,7 +74,7 @@ const stackinuse = function(L) {
     for (let ci = L.ci; ci !== null; ci = ci.previous) {
         if (lim < ci.top) lim = ci.top;
     }
-    assert(lim <= L.stack.length);
+    assert(lim <= L.stack_last);
     return lim + 1; /* part of stack in use */
 };
 
@@ -107,7 +108,7 @@ const luaD_precall = function(L, off, nresults) {
             ci.nresults = nresults;
             ci.func = func;
             ci.top = L.top + defs.LUA_MINSTACK;
-            assert(ci.top <= L.stack.length);
+            assert(ci.top <= L.stack_last);
             ci.callstatus = 0;
             if (L.hookmask & defs.LUA_MASKCALL)
                 luaD_hook(L, defs.LUA_HOOKCALL, -1);
@@ -219,6 +220,7 @@ const luaD_hook = function(L, event, line) {
         ar.currentline = line;
         ar.i_ci = ci;
         ci.top = L.top + defs.LUA_MINSTACK;
+        assert(ci.top <= L.stack_last);
         L.allowhook = 0;  /* cannot call hooks inside a hook */
         ci.callstatus |= lstate.CIST_HOOKED;
         hook(L, ar);
diff --git a/src/lstate.js b/src/lstate.js
index 5481f95..b71e011 100644
--- a/src/lstate.js
+++ b/src/lstate.js
@@ -49,7 +49,8 @@ class lua_State {
         this.base_ci = new CallInfo(); // Will be populated later
         this.top = 0;
         this.ci = null;
-        this.stack = [];
+        this.stack = null;
+        this.stack_last = NaN;
         this.openupval = null;
         this.status = TS.LUA_OK;
         this.next = null;
@@ -86,8 +87,10 @@ const luaE_extendCI = function(L) {
 };
 
 const stack_init = function(L1, L) {
-    L1.stack = new Array(BASIC_STACK_SIZE); // TODO: for now we don't care about the stack size
+    L1.stack = new Array(BASIC_STACK_SIZE);
     L1.top = 0;
+    L1.stack_last = BASIC_STACK_SIZE - EXTRA_STACK;
+    /* initialize first ci */
     let ci = L1.base_ci;
     ci.next = ci.previous = null;
     ci.callstatus = 0;