From 1333b3837d405c31baaa44d1db89aab0f7d09349 Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Thu, 11 Dec 2014 21:30:35 +1000
Subject: Avoid unbounded stack consumption for synchronous control flow

Previously, as sequence of state transitions that did not pass through
an asynchrous boundary incurred stack frames. The trivial loop in
the enclosed test case would then overflow the stack.

This commit merges the `resume` and `apply(tr: Try[Any])` methods into
a `apply`. It changes the body of this method to be an infinite loop
with returns at the terminal points in the state machine (or at a
terminal failure.)

To allow merging of these previously separate matches, states that
contain an await are now allocated two state ids: one for the setup
code that calls `onComplete`, and one for the code in the continuation
that records the result and advances the state machine.

Fixes #93
---
 src/test/scala/scala/async/TreeInterrogation.scala |  4 ++--
 .../scala/scala/async/run/futures/FutureSpec.scala |  7 ++++++
 .../run/stackoverflow/StackOverflowSpec.scala      | 28 ++++++++++++++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)
 create mode 100644 src/test/scala/scala/async/run/stackoverflow/StackOverflowSpec.scala

(limited to 'src/test')

diff --git a/src/test/scala/scala/async/TreeInterrogation.scala b/src/test/scala/scala/async/TreeInterrogation.scala
index 8261898..b7c403a 100644
--- a/src/test/scala/scala/async/TreeInterrogation.scala
+++ b/src/test/scala/scala/async/TreeInterrogation.scala
@@ -36,7 +36,7 @@ class TreeInterrogation {
     functions.size mustBe 1
 
     val varDefs = tree1.collect {
-      case ValDef(mods, name, _, _) if mods.hasFlag(Flag.MUTABLE) => name
+      case vd @ ValDef(mods, name, _, _) if mods.hasFlag(Flag.MUTABLE) && vd.symbol.owner.isClass => name
     }
     varDefs.map(_.decoded.trim).toSet mustBe (Set("state", "await$1$1", "await$2$1"))
 
@@ -49,7 +49,7 @@ class TreeInterrogation {
               && !dd.symbol.asTerm.isAccessor && !dd.symbol.asTerm.isSetter => dd.name
         }
     }.flatten
-    defDefs.map(_.decoded.trim).toSet mustBe (Set("foo$1", "apply", "resume", "<init>"))
+    defDefs.map(_.decoded.trim).toSet mustBe (Set("foo$1", "apply", "<init>"))
   }
 }
 
diff --git a/src/test/scala/scala/async/run/futures/FutureSpec.scala b/src/test/scala/scala/async/run/futures/FutureSpec.scala
index 1761db5..25be0b1 100644
--- a/src/test/scala/scala/async/run/futures/FutureSpec.scala
+++ b/src/test/scala/scala/async/run/futures/FutureSpec.scala
@@ -134,6 +134,13 @@ class FutureSpec {
       Await.result(future1, defaultTimeout) mustBe ("10-14")
       intercept[NoSuchElementException] { Await.result(future2, defaultTimeout) }
     }
+
+    @Test def mini() {
+      val future4 = async {
+        await(Future.successful(0)).toString
+      }
+      Await.result(future4, defaultTimeout)
+    }
     
     @Test def `recover from exceptions`() {
       val future1 = Future(5)
diff --git a/src/test/scala/scala/async/run/stackoverflow/StackOverflowSpec.scala b/src/test/scala/scala/async/run/stackoverflow/StackOverflowSpec.scala
new file mode 100644
index 0000000..2dc9b92
--- /dev/null
+++ b/src/test/scala/scala/async/run/stackoverflow/StackOverflowSpec.scala
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2012-2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package scala.async
+package run
+package stackoverflow
+
+import org.junit.Test
+import scala.async.internal.AsyncId
+
+
+class StackOverflowSpec {
+
+  @Test
+  def stackSafety() {
+    import AsyncId._
+    async {
+      var i = 100000000
+      while (i > 0) {
+        if (false) {
+          await(())
+        }
+        i -= 1
+      }
+    }
+  }
+}
-- 
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