Leak folly::SingletonVault

Summary: This will ensure SingletonVault is always available. It matters for singletons, not managed by folly::Singleton. Singletons in it will actually be destroyed via static SingletonVaultDestructor.

Test Plan: unit test

Reviewed By: chip@fb.com

Subscribers: njormrod

FB internal diff: D1591270

folly/experimental/Singleton.cpp

@@ -55,7 +55,21 @@ void SingletonVault::destroyInstances() {
 }
 
 SingletonVault* SingletonVault::singleton() {
-  static SingletonVault vault;
-  return &vault;
+  static SingletonVault* vault = new SingletonVault();
+  return vault;
 }
+
+namespace {
+
+class SingletonVaultDestructor {
+ public:
+  ~SingletonVaultDestructor() {
+    SingletonVault::singleton()->destroyInstances();
+  }
+};
+
+SingletonVaultDestructor singletonVaultDestructor;
+
+}
+
 }

folly/experimental/Singleton.h

@@ -167,6 +167,8 @@ class SingletonVault {
   enum class Type { Strict, Relaxed };
 
   explicit SingletonVault(Type type = Type::Relaxed) : type_(type) {}
+
+  // Destructor is only called by unit tests to check destroyInstances.
   ~SingletonVault();
 
   typedef std::function<void(void*)> TeardownFunc;