Internal change

PiperOrigin-RevId: 532934867

mediapipe/framework/BUILD

@@ -1099,6 +1099,7 @@ cc_library(
         "//mediapipe/framework/port:ret_check",
         "//mediapipe/framework/port:status",
     ],
+    alwayslink = True,  # Defines TestServiceCalculator
 )
 
 cc_library(

mediapipe/framework/graph_service.h

@@ -44,7 +44,6 @@ class GraphServiceBase {
 
   constexpr GraphServiceBase(const char* key) : key(key) {}
 
-  virtual ~GraphServiceBase() = default;
   inline virtual absl::StatusOr<Packet> CreateDefaultObject() const {
     return DefaultInitializationUnsupported();
   }
@@ -52,14 +51,32 @@ class GraphServiceBase {
   const char* key;
 
  protected:
+  // `GraphService<T>` objects, deriving `GraphServiceBase` are designed to be
+  // global constants and not ever deleted through `GraphServiceBase`. Hence,
+  // protected and non-virtual destructor which helps to make `GraphService<T>`
+  // trivially destructible and properly defined as global constants.
+  //
+  // A class with any virtual functions should have a destructor that is either
+  // public and virtual or else protected and non-virtual.
+  // https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rc-dtor-virtual
+  ~GraphServiceBase() = default;
+
   absl::Status DefaultInitializationUnsupported() const {
     return absl::UnimplementedError(absl::StrCat(
         "Graph service '", key, "' does not support default initialization"));
   }
 };
 
+// A global constant to refer a service:
+// - Requesting `CalculatorContract::UseService` from calculator
+// - Accessing `Calculator/SubgraphContext::Service`from calculator/subgraph
+// - Setting before graph initialization `CalculatorGraph::SetServiceObject`
+//
+// NOTE: In headers, define your graph service reference safely as following:
+// `inline constexpr GraphService<YourService> kYourService("YourService");`
+//
 template <typename T>
-class GraphService : public GraphServiceBase {
+class GraphService final : public GraphServiceBase {
  public:
   using type = T;
   using packet_type = std::shared_ptr<T>;
@@ -68,7 +85,7 @@ class GraphService : public GraphServiceBase {
                                                  kDisallowDefaultInitialization)
       : GraphServiceBase(my_key), default_init_(default_init) {}
 
-  absl::StatusOr<Packet> CreateDefaultObject() const override {
+  absl::StatusOr<Packet> CreateDefaultObject() const final {
     if (default_init_ != kAllowDefaultInitialization) {
       return DefaultInitializationUnsupported();
     }

mediapipe/framework/graph_service_manager_test.cc

@@ -7,7 +7,7 @@
 
 namespace mediapipe {
 namespace {
-const GraphService<int> kIntService("mediapipe::IntService");
+constexpr GraphService<int> kIntService("mediapipe::IntService");
 }  // namespace
 
 TEST(GraphServiceManager, SetGetServiceObject) {

mediapipe/framework/graph_service_test.cc

@@ -14,6 +14,8 @@
 
 #include "mediapipe/framework/graph_service.h"
 
+#include <type_traits>
+
 #include "mediapipe/framework/calculator_contract.h"
 #include "mediapipe/framework/calculator_framework.h"
 #include "mediapipe/framework/port/canonical_errors.h"
@@ -159,7 +161,7 @@ TEST_F(GraphServiceTest, CreateDefault) {
 
 struct TestServiceData {};
 
-const GraphService<TestServiceData> kTestServiceAllowDefaultInitialization(
+constexpr GraphService<TestServiceData> kTestServiceAllowDefaultInitialization(
     "kTestServiceAllowDefaultInitialization",
     GraphServiceBase::kAllowDefaultInitialization);
 
@@ -272,9 +274,13 @@ TEST(AllowDefaultInitializationGraphServiceTest,
                        HasSubstr("Service is unavailable.")));
 }
 
-const GraphService<TestServiceData> kTestServiceDisallowDefaultInitialization(
+constexpr GraphService<TestServiceData>
-    "kTestServiceDisallowDefaultInitialization",
+    kTestServiceDisallowDefaultInitialization(
-    GraphServiceBase::kDisallowDefaultInitialization);
+        "kTestServiceDisallowDefaultInitialization",
+        GraphServiceBase::kDisallowDefaultInitialization);
+
+static_assert(std::is_trivially_destructible_v<GraphService<TestServiceData>>,
+              "GraphService is not trivially destructible");
 
 class FailOnUnavailableOptionalDisallowDefaultInitServiceCalculator
     : public CalculatorBase {

mediapipe/framework/test_service.cc

@@ -16,15 +16,6 @@
 
 namespace mediapipe {
 
-const GraphService<TestServiceObject> kTestService(
-    "test_service", GraphServiceBase::kDisallowDefaultInitialization);
-const GraphService<int> kAnotherService(
-    "another_service", GraphServiceBase::kAllowDefaultInitialization);
-const GraphService<NoDefaultConstructor> kNoDefaultService(
-    "no_default_service", GraphServiceBase::kAllowDefaultInitialization);
-const GraphService<NeedsCreateMethod> kNeedsCreateService(
-    "needs_create_service", GraphServiceBase::kAllowDefaultInitialization);
-
 absl::Status TestServiceCalculator::GetContract(CalculatorContract* cc) {
   cc->Inputs().Index(0).Set<int>();
   cc->Outputs().Index(0).SetSameAs(&cc->Inputs().Index(0));

mediapipe/framework/test_service.h

@@ -22,14 +22,17 @@ namespace mediapipe {
 
 using TestServiceObject = std::map<std::string, int>;
 
-extern const GraphService<TestServiceObject> kTestService;
+inline constexpr GraphService<TestServiceObject> kTestService(
-extern const GraphService<int> kAnotherService;
+    "test_service", GraphServiceBase::kDisallowDefaultInitialization);
+inline constexpr GraphService<int> kAnotherService(
+    "another_service", GraphServiceBase::kAllowDefaultInitialization);
 
 class NoDefaultConstructor {
  public:
   NoDefaultConstructor() = delete;
 };
-extern const GraphService<NoDefaultConstructor> kNoDefaultService;
+inline constexpr GraphService<NoDefaultConstructor> kNoDefaultService(
+    "no_default_service", GraphServiceBase::kAllowDefaultInitialization);
 
 class NeedsCreateMethod {
  public:
@@ -40,7 +43,8 @@ class NeedsCreateMethod {
  private:
   NeedsCreateMethod() = default;
 };
-extern const GraphService<NeedsCreateMethod> kNeedsCreateService;
+inline constexpr GraphService<NeedsCreateMethod> kNeedsCreateService(
+    "needs_create_service", GraphServiceBase::kAllowDefaultInitialization);
 
 // Use a service.
 class TestServiceCalculator : public CalculatorBase {