flipper | Replace global static variables in FlipperSocketProvider with local static.

Summary: Replacing global static varaibles with local static. No cost at startup time, and also fixes any potential static initialization order fiasco.

Differential Revision: D45900297

fbshipit-source-id: 80e3ffb6527f7f7b6b08de4a6209f0f8298f7bf5

xplat/Flipper/FlipperSocketProvider.cpp

@@ -12,17 +12,18 @@
 namespace facebook {
 namespace flipper {
 
-std::unique_ptr<FlipperSocketProvider> FlipperSocketProvider::provider_ =
-    nullptr;
-
-std::unique_ptr<FlipperSocketProvider> FlipperSocketProvider::shelvedProvider_ =
-    nullptr;
+std::unique_ptr<FlipperSocketProvider>&
+FlipperSocketProvider::defaultProvider() {
+  static std::unique_ptr<FlipperSocketProvider> provider;
+  return provider;
+}
 
 std::unique_ptr<FlipperSocket> FlipperSocketProvider::socketCreate(
     FlipperConnectionEndpoint endpoint,
     std::unique_ptr<FlipperSocketBasePayload> payload,
     Scheduler* scheduler) {
-  return provider_->create(std::move(endpoint), std::move(payload), scheduler);
+  return defaultProvider()->create(
+      std::move(endpoint), std::move(payload), scheduler);
 }
 
 std::unique_ptr<FlipperSocket> FlipperSocketProvider::socketCreate(
@@ -30,7 +31,7 @@ std::unique_ptr<FlipperSocket> FlipperSocketProvider::socketCreate(
     std::unique_ptr<FlipperSocketBasePayload> payload,
     Scheduler* scheduler,
     ConnectionContextStore* connectionContextStore) {
-  return provider_->create(
+  return defaultProvider()->create(
       std::move(endpoint),
       std::move(payload),
       scheduler,
@@ -39,11 +40,11 @@ std::unique_ptr<FlipperSocket> FlipperSocketProvider::socketCreate(
 
 void FlipperSocketProvider::setDefaultProvider(
     std::unique_ptr<FlipperSocketProvider> provider) {
-  provider_ = std::move(provider);
+  defaultProvider() = std::move(provider);
 }
 
 bool FlipperSocketProvider::hasProvider() {
-  return provider_ != nullptr;
+  return defaultProvider() != nullptr;
 }
 
 } // namespace flipper