Fixes #1326

.jshintrc

@@ -88,7 +88,9 @@
         "CALLBACK_PROMISE_OFFSET": false,
         "CALLBACK_RECEIVER_OFFSET": false,
         "CALLBACK_SIZE": false,
+        "ASYNC_GUARANTEE_SHIFT": false,
         "NO_STATE": false,
+        "NO_ASYNC_GUARANTEE": false,
         "RETURNED_NON_UNDEFINED": false,
         "IS_ASYNC_GUARANTEED": false,
         "IS_FOLLOWING": false,

src/constants.js

@@ -28,10 +28,11 @@ CONSTANT(CALLBACK_PROMISE_OFFSET, 2);
 CONSTANT(CALLBACK_RECEIVER_OFFSET, 3);
 CONSTANT(CALLBACK_SIZE, 4);
 //Layout for ._bitField
-//[RR]RO GWFN CTBH IUDE LLLL LLLL LLLL LLLL
+//[RR]XO GWFN CTBH IUDE LLLL LLLL LLLL LLLL
 //[RR] = [Reserved] (Both bits are either on or off to represent
 //                    1 bit due to 31-bit integers in 32-bit v8)
 //R = [Reserved]
+//X = noAsyncGuarantee
 //O = returnedNonUndefined
 //G = isAsyncGuaranteed
 //W = isFollowing (The promise that is being followed is not stored explicitly)
@@ -46,7 +47,9 @@ CONSTANT(CALLBACK_SIZE, 4);
 //D = isDisposable
 //E = isCancelled
 //L = Length, 16 bit unsigned
+CONSTANT(ASYNC_GUARANTEE_SHIFT, 2)
 CONSTANT(NO_STATE, 0x0|0);
+CONSTANT(NO_ASYNC_GUARANTEE, 0x20000000|0);
 CONSTANT(RETURNED_NON_UNDEFINED, 0x10000000|0);
 CONSTANT(IS_ASYNC_GUARANTEED, 0x8000000|0);
 CONSTANT(IS_FOLLOWING, 0x4000000|0);

src/promise.js

@@ -360,7 +360,15 @@ Promise.prototype._setWillBeCancelled = function() {
 
 Promise.prototype._setAsyncGuaranteed = function() {
     if (async.hasCustomScheduler()) return;
-    this._bitField = this._bitField | IS_ASYNC_GUARANTEED;
+    var bitField = this._bitField;
+    this._bitField = bitField |
+        (((bitField & NO_ASYNC_GUARANTEE) >> ASYNC_GUARANTEE_SHIFT) ^
+        IS_ASYNC_GUARANTEED);
+};
+
+Promise.prototype._setNoAsyncGuarantee = function() {
+    this._bitField = (this._bitField | NO_ASYNC_GUARANTEE) &
+        (~IS_ASYNC_GUARANTEED);
 };
 
 Promise.prototype._receiverAt = function (index) {

src/reduce.js

@@ -110,7 +110,14 @@ ReductionPromiseArray.prototype._iterate = function (values) {
                 length: length,
                 array: this
             };
+
             value = value._then(gotAccum, undefined, undefined, ctx, undefined);
+
+            // Too many promises chained with asyncGuaranteed will result in
+            // stack overflow. Break up long chains to reset stack.
+            if ((i & 127) === 0) {
+                value._setNoAsyncGuarantee();
+            }
         }
     }