---

yaml
---
r: 347369
b: refs/heads/master
c: 9e0d07e
h: refs/heads/master
i:
  347367: 06be74d

Author: swift-ci

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: dffedaa1888ef755e9e933a2cf0bb0185aa31c47
+refs/heads/master: 9e0d07eefc1cbecd1f8d97086dfe304490e28c16
 refs/heads/master-next: 203b3026584ecad859eb328b2e12490099409cd5
 refs/tags/osx-passed: b6b74147ef8a386f532cf9357a1bde006e552c54
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-a: 6bb18e013c2284f2b45f5f84f2df2887dc0f7dea

trunk/stdlib/public/core/Array.swift

@@ -1162,7 +1162,10 @@ extension Array: RangeReplaceableCollection {
       "newElements.underestimatedCount was an overestimate")
     // can't check for overflow as sequences can underestimate
 
-    _buffer.count += writtenCount
+    // This check prevents a data race writting to _swiftEmptyArrayStorage
+    if writtenCount > 0 {
+      _buffer.count += writtenCount
+    }
 
     if writtenUpTo == buf.endIndex {
       // there may be elements that didn't fit in the existing buffer,

trunk/test/PlaygroundTransform/Inputs/not.py

@@ -7,7 +7,7 @@
     sys.exit(0)
 
 try:
-    subprocess.check_call(shlex.split(' '.join(sys.argv[1:])))
+    subprocess.check_call(shlex.split(sys.argv[1]))
     sys.exit(1)
 except subprocess.CalledProcessError as e:
     sys.exit(0)

trunk/test/Sanitizers/tsan-emptyarraystorage.swift

@@ -0,0 +1,40 @@
+// RUN: %target-swiftc_driver %s -target %sanitizers-target-triple -g -sanitize=thread -o %t_tsan-binary
+// RUN: %target-codesign %t_tsan-binary
+// RUN: %target-run %t_tsan-binary 2>&1 | %FileCheck %s
+// REQUIRES: executable_test
+// REQUIRES: tsan_runtime
+// UNSUPPORTED: OS=tvos
+
+// FIXME: This should be covered by "tsan_runtime"; older versions of Apple OSs
+// don't support TSan.
+// UNSUPPORTED: remote_run
+
+import Foundation
+
+let sem = DispatchSemaphore(value: 0)
+
+class T1: Thread {
+  override func main() {
+    var oneEmptyArray: [[String:String]] = []
+    oneEmptyArray.append(contentsOf: [])
+    sem.signal()
+  }
+}
+let t1 = T1()
+t1.start()
+
+class T2: Thread {
+  override func main() {
+    var aCompletelyUnrelatedOtherEmptyArray: [[Double:Double]] = []
+    aCompletelyUnrelatedOtherEmptyArray.append(contentsOf: [])
+    sem.signal()
+  }
+}
+let t2 = T2()
+t2.start()
+
+sem.wait()
+sem.wait()
+print("Done!")
+
+// CHECK: Done!