Init the std::atomic since in the default constructor is "no initialization takes place"

Summary: Init the std::atomic since in the default constructor is "no initialization takes place"

Reviewed By: yfeldblum, djwatson

Differential Revision: D9515004

fbshipit-source-id: cdc73c490f77496335e77732b0c7c43c180a54b6

folly/experimental/hazptr/test/HazptrTest.cpp

@@ -516,7 +516,7 @@ TEST_F(HazptrTest, mt_refcount) {
 
   std::atomic<bool> ready(false);
   std::atomic<int> setHazptrs(0);
-  std::atomic<Foo*> head;
+  std::atomic<Foo*> head{nullptr};
 
   int num = 20;
   int nthr = 10;

folly/test/AtomicUnorderedMapTest.cpp

@@ -246,7 +246,7 @@ void contendedRW(size_t itersPerThread,
   typedef AtomicUnorderedInsertMap<Key,MutableAtom<uint32_t>,PairHash> Map;
 
   std::unique_ptr<Map> ptr = {};
-  std::atomic<bool> go;
+  std::atomic<bool> go{false};
   std::vector<std::thread> threads;
 
   BENCHMARK_SUSPEND {

folly/test/SingletonTest.cpp

@@ -530,7 +530,7 @@ TEST(Singleton, SingletonEagerInitParallel) {
   const static size_t kIters = 1000;
   const static size_t kThreads = 20;
 
-  std::atomic<size_t> initCounter;
+  std::atomic<size_t> initCounter{0};
 
   auto& vault = *SingletonVault::singleton<EagerInitParallelTag>();
 

folly/test/ThreadLocalTest.cpp

@@ -335,8 +335,7 @@ TEST(ThreadLocalPtr, AccessAllThreadsCounter) {
   const int kNumThreads = 256;
   SimpleThreadCachedInt stci[kNumThreads + 1];
   std::atomic<bool> run(true);
-  std::atomic<int> totalAtomic;
-  ;
+  std::atomic<int> totalAtomic{0};
   std::vector<std::thread> threads;
   // thread i will increment all the thread locals
   // in the range 0..i