SI-7814 Avoid init cycle between Predef, `package`, ScalaRuntime

Not every application will force these in a single thread; we
have to do our best to avoid cycles between them.

The enclosed test was failing every time before the change.

This commit breaks the cycle by avoiding computing `tupleNames`
in the constructor of `ScalaRuntime`. The new version has the
added benefit of including specialized tuple subclasses, which
is verified with a unit test for `isTuple`.

Are there more of these lurking? It seems likely. I'm more than
a little concerned about the way the `ControlThrowable` fires up
`scala.SystemProperties` to check whether or not to suppress
stack traces; there is already an ugly hack in place:

    object NoStackTrace {
      final def noSuppression = _noSuppression

      // two-stage init to make checkinit happy,
      // since sys.SystemProperties.noTraceSupression.value
      // calls back into NoStackTrace.noSuppression
      final private var _noSuppression = false
      _noSuppression = sys.SystemProperties.noTraceSupression.value
    }

3 files changed, 144 insertions, 11 deletions

diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 1d8fe5e9ad..4fee6d75a3 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -34,21 +34,13 @@ object ScalaRunTime {
     clazz.isArray && (atLevel == 1 || isArrayClass(clazz.getComponentType, atLevel - 1))
 
   def isValueClass(clazz: jClass[_]) = clazz.isPrimitive()
-  def isTuple(x: Any) = x != null && tupleNames(x.getClass.getName)
+
+  // includes specialized subclasses and future proofed against hypothetical TupleN (for N > 22)
+  def isTuple(x: Any) = x != null && x.getClass.getName.startsWith("scala.Tuple")
   def isAnyVal(x: Any) = x match {
     case _: Byte | _: Short | _: Char | _: Int | _: Long | _: Float | _: Double | _: Boolean | _: Unit => true
     case _                                                                                             => false
   }
-  // Avoiding boxing which messes up the specialized tests.  Don't ask.
-  private val tupleNames = {
-    var i = 22
-    var names: List[String] = Nil
-    while (i >= 1) {
-      names ::= ("scala.Tuple" + String.valueOf(i))
-      i -= 1
-    }
-    names.toSet
-  }
 
   /** Return the class object representing an array with element class `clazz`.
    */
diff --git a/test/files/run/predef-cycle.scala b/test/files/run/predef-cycle.scala
new file mode 100644
index 0000000000..ab147688bc
--- /dev/null
+++ b/test/files/run/predef-cycle.scala
@@ -0,0 +1,71 @@
+class Force {
+	val t1 = new Thread {
+    override def run() {
+      scala.`package`
+    }
+  }
+  val t2 = new Thread {
+    override def run() {
+      scala.Predef
+    }
+  }
+  t1.start()
+  t2.start()
+  t1.join()
+  t2.join()
+}
+
+object Test {
+  def main(args: Array[String]) {
+     new Force()
+  }
+}
+
+/* Was deadlocking:
+"Thread-2" prio=5 tid=7f9637268000 nid=0x119601000 in Object.wait() [119600000]
+   java.lang.Thread.State: RUNNABLE
+  at scala.Predef$.<init>(Predef.scala:90)
+  at scala.Predef$.<clinit>(Predef.scala)
+  at Force$$anon$2.run(predef-cycle.scala:10)
+
+"Thread-1" prio=5 tid=7f9637267800 nid=0x1194fe000 in Object.wait() [1194fb000]
+   java.lang.Thread.State: RUNNABLE
+  at scala.collection.immutable.Set$Set4.$plus(Set.scala:127)
+  at scala.collection.immutable.Set$Set4.$plus(Set.scala:121)
+  at scala.collection.mutable.SetBuilder.$plus$eq(SetBuilder.scala:24)
+  at scala.collection.mutable.SetBuilder.$plus$eq(SetBuilder.scala:22)
+  at scala.collection.generic.Growable$$anonfun$$plus$plus$eq$1.apply(Growable.scala:48)
+  at scala.collection.generic.Growable$$anonfun$$plus$plus$eq$1.apply(Growable.scala:48)
+  at scala.collection.immutable.List.foreach(List.scala:318)
+  at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:48)
+  at scala.collection.mutable.SetBuilder.$plus$plus$eq(SetBuilder.scala:22)
+  at scala.collection.TraversableLike$class.to(TraversableLike.scala:629)
+  at scala.collection.AbstractTraversable.to(Traversable.scala:105)
+  at scala.collection.TraversableOnce$class.toSet(TraversableOnce.scala:267)
+  at scala.collection.AbstractTraversable.toSet(Traversable.scala:105)
+  at scala.runtime.ScalaRunTime$.<init>(ScalaRunTime.scala:50)
+  at scala.runtime.ScalaRunTime$.<clinit>(ScalaRunTime.scala)
+  at scala.collection.mutable.HashTable$HashUtils$class.elemHashCode(HashTable.scala)
+  at scala.collection.mutable.HashMap.elemHashCode(HashMap.scala:39)
+  at scala.collection.mutable.HashTable$class.findOrAddEntry(HashTable.scala:161)
+  at scala.collection.mutable.HashMap.findOrAddEntry(HashMap.scala:39)
+  at scala.collection.mutable.HashMap.put(HashMap.scala:75)
+  at scala.collection.mutable.HashMap.update(HashMap.scala:80)
+  at scala.sys.SystemProperties$.addHelp(SystemProperties.scala:64)
+  at scala.sys.SystemProperties$.bool(SystemProperties.scala:68)
+  at scala.sys.SystemProperties$.noTraceSupression$lzycompute(SystemProperties.scala:80)
+  - locked <7b8b0e228> (a scala.sys.SystemProperties$)
+  at scala.sys.SystemProperties$.noTraceSupression(SystemProperties.scala:80)
+  at scala.util.control.NoStackTrace$.<init>(NoStackTrace.scala:31)
+  at scala.util.control.NoStackTrace$.<clinit>(NoStackTrace.scala)
+  at scala.util.control.NoStackTrace$class.fillInStackTrace(NoStackTrace.scala:22)
+  at scala.util.control.BreakControl.fillInStackTrace(Breaks.scala:93)
+  at java.lang.Throwable.<init>(Throwable.java:181)
+  at scala.util.control.BreakControl.<init>(Breaks.scala:93)
+  at scala.util.control.Breaks.<init>(Breaks.scala:28)
+  at scala.collection.Traversable$.<init>(Traversable.scala:96)
+  at scala.collection.Traversable$.<clinit>(Traversable.scala)
+  at scala.package$.<init>(package.scala:46)
+  at scala.package$.<clinit>(package.scala)
+  at Force$$anon$1.run(predef-cycle.scala:4)
+  */
\ No newline at end of file
diff --git a/test/junit/scala/runtime/ScalaRunTimeTest.scala b/test/junit/scala/runtime/ScalaRunTimeTest.scala
new file mode 100644
index 0000000000..9da197c71a
--- /dev/null
+++ b/test/junit/scala/runtime/ScalaRunTimeTest.scala
@@ -0,0 +1,70 @@
+package scala.runtime
+
+import org.junit.Assert._
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+/** Tests for the private class DefaultPromise */
+@RunWith(classOf[JUnit4])
+class ScalaRunTimeTest {
+  @Test
+  def testIsTuple() {
+    import ScalaRunTime.isTuple
+    def check(v: Any) = {
+      assertTrue(v.toString, isTuple(v))
+    }
+
+    val s = ""
+    check(Tuple1(s))
+    check((s, s))
+    check((s, s, s))
+    check((s, s, s, s))
+    check((s, s, s, s, s))
+    check((s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+    check((s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s, s))
+
+    // some specialized variants will have mangled classnames
+    check(Tuple1(0))
+    check((0, 0))
+    check((0, 0, 0))
+    check((0, 0, 0, 0))
+    check((0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+    check((0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
+
+    case class C()
+    val c = new C()
+    assertFalse(c.toString, isTuple(c))
+  }
+}