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include/grpc++/server.h

@@ -91,9 +91,15 @@ class Server GRPC_FINAL : public GrpcLibrary, private CallHook {
   /// a server event occurs
   class GlobalCallbacks {
    public:
+    virtual ~GlobalCallbacks() {}
+    /// Called before application callback for each synchronous server request
     virtual void PreSynchronousRequest(ServerContext* context) = 0;
+    /// Called after application callback for each synchronous server request
     virtual void PostSynchronousRequest(ServerContext* context) = 0;
   };
+  /// Set the global callback object. Can only be called once. Does not take
+  /// ownership of callbacks, and expects the pointed to object to be alive
+  /// until all server objects in the process have been destroyed.
   static void SetGlobalCallbacks(GlobalCallbacks* callbacks);
 
  private:

src/cpp/server/server.cc

@@ -57,8 +57,17 @@ class DefaultGlobalCallbacks GRPC_FINAL : public Server::GlobalCallbacks {
   void PostSynchronousRequest(ServerContext* context) GRPC_OVERRIDE {}
 };
 
-static DefaultGlobalCallbacks g_default_callbacks;
-static Server::GlobalCallbacks* g_callbacks = &g_default_callbacks;
+static Server::GlobalCallbacks* g_callbacks = nullptr;
+static gpr_once g_once_init_callbacks = GPR_ONCE_INIT;
+
+static void DeleteGlobalCallbacks() { delete g_callbacks; }
+
+static void InitGlobalCallbacks() {
+  if (g_callbacks == nullptr) {
+    g_callbacks = new DefaultGlobalCallbacks();
+    atexit(DeleteGlobalCallbacks);
+  }
+}
 
 class Server::UnimplementedAsyncRequestContext {
  protected:
@@ -294,6 +303,7 @@ Server::Server(ThreadPoolInterface* thread_pool, bool thread_pool_owned,
       server_(CreateServer(max_message_size, compression_options)),
       thread_pool_(thread_pool),
       thread_pool_owned_(thread_pool_owned) {
+  gpr_once_init(&g_once_init_callbacks, InitGlobalCallbacks);
   grpc_server_register_completion_queue(server_, cq_.cq(), nullptr);
 }
 
@@ -316,9 +326,8 @@ Server::~Server() {
 }
 
 void Server::SetGlobalCallbacks(GlobalCallbacks* callbacks) {
-  GPR_ASSERT(g_callbacks == &g_default_callbacks);
-  GPR_ASSERT(callbacks != NULL);
-  GPR_ASSERT(callbacks != &g_default_callbacks);
+  GPR_ASSERT(g_callbacks == nullptr);
+  GPR_ASSERT(callbacks != nullptr);
   g_callbacks = callbacks;
 }