Merge pull request #899 from leapmotion/bug-deferredteardown

Correct invalid deferred destruction

src/autowiring/CoreContext.h

@@ -584,6 +584,10 @@ class CoreContext:
         return memo.m_value.template as<T>();
     }
 
+    // Need the memo for the actual type at this point, if we don't hold this down then this
+    // entry might not get constructed.
+    auto& memo = FindByType(auto_id_t<typename CreationRules::TActual>{}, true);
+
     // We must make ourselves current for the remainder of this call:
     CurrentContextPusher pshr(shared_from_this());
     std::shared_ptr<typename CreationRules::TActual> retVal(
@@ -607,7 +611,6 @@ class CoreContext:
       // we will simply eat this exception, and handle it silently by returning the type that
       // someone else has already attempted to construct, as per the documented behavior of
       // Construct.
-      auto& memo = FindByType(auto_id_t<typename CreationRules::TActual>{}, true);
       retVal = memo.m_value.template as<typename CreationRules::TActual>();
     }
 

src/autowiring/test/CoreContextTest.cpp

@@ -636,3 +636,53 @@ TEST_F(CoreContextTest, AwaitTimed) {
 
   injector.join();
 }
+
+namespace {
+  class HoldsMutexAndCount {
+  public:
+    volatile int hitCount = 0;
+    int initCount = 0;
+    int instanceCount = 0;
+    std::mutex lk;
+  };
+
+  class DelaysWithNwa {
+  public:
+    DelaysWithNwa(void) {
+      hmac->hitCount++;
+      std::lock_guard<std::mutex>{ hmac->lk };
+
+      hmac->initCount++;
+      hmac->instanceCount++;
+    }
+
+    virtual ~DelaysWithNwa(void) {
+      hmac->instanceCount--;
+    }
+
+    AutoRequired<HoldsMutexAndCount> hmac;
+  };
+}
+
+TEST_F(CoreContextTest, SimultaneousMultiInject) {
+  AutoCreateContext ctxt;
+  AutoRequired<HoldsMutexAndCount> hmac{ ctxt };
+
+  std::unique_lock<std::mutex> lk{ hmac->lk };
+  std::thread a([ctxt] { ctxt->Inject<DelaysWithNwa>(); });
+  std::thread b([ctxt] { ctxt->Inject<DelaysWithNwa>(); });
+
+  // Poor man's barrier
+  while (hmac->hitCount != 2)
+    std::this_thread::yield();
+  lk.unlock();
+
+  a.join();
+  b.join();
+
+  // Two initializations should have taken place due to the barrier
+  ASSERT_EQ(2, hmac->initCount);
+
+  // Only one of those two instances should still be around
+  ASSERT_EQ(1, hmac->instanceCount);
+}