Add unit test for fix of plugin EP library handle leak in PR 28396

onnxruntime/test/autoep/test_handle_leak.cc

@@ -0,0 +1,114 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#include <filesystem>
+#include <gsl/gsl>
+#include <memory>
+#include <optional>
+#include <string>
+#include <gtest/gtest.h>
+
+#include "core/session/onnxruntime_cxx_api.h"
+
+#include "test/autoep/test_autoep_utils.h"
+#include "test/util/include/file_util.h"
+#include "test/util/include/temp_dir.h"
+
+#if defined(_WIN32)
+#include <windows.h>
+#else
+#include <dlfcn.h>
+#endif
+
+extern std::unique_ptr<Ort::Env> ort_env;
+
+namespace onnxruntime {
+namespace test {
+
+namespace {
+
+// Returns whether the library is currently mapped in the process, or std::nullopt if the platform
+// does not support querying loaded-library state without side effects.
+// On Windows, GetModuleHandleW queries by filename without incrementing the refcount.
+// On Linux/macOS, dlopen with RTLD_NOLOAD probes without loading; if it succeeds it adds a
+// refcount that we immediately release with dlclose.
+std::optional<bool> IsLibraryLoaded(const std::filesystem::path& library_path) {
+#if defined(_WIN32)
+  return GetModuleHandleW(library_path.filename().wstring().c_str()) != nullptr;
+#else
+#ifdef RTLD_NOLOAD
+  void* handle = dlopen(library_path.c_str(), RTLD_NOLOAD | RTLD_NOW);
+  if (handle) {
+    dlclose(handle);  // Undo the refcount added by the RTLD_NOLOAD probe.
+    return true;
+  }
+  return false;
+#else
+  // RTLD_NOLOAD is not available on this platform; cannot probe without loading.
+  static_cast<void>(library_path);
+  return std::nullopt;
+#endif
+#endif
+}
+
+}  // namespace
+
+// Verify that registering and unregistering a plugin EP library does not leak the library handle.
+//
+// ProviderLibrary::Load() loads the library then probes for the "GetProvider" symbol. Most plugin EP
+// libraries do not export "GetProvider", so the probe fails. Without the fix (PR #28396),
+// Load() returned the error without calling Unload(), leaving a leaked refcount. After
+// UnregisterExecutionProviderLibrary released only the EpLibraryPlugin's reference, the library
+// remained mapped in the process.
+//
+// To ensure this test is independent of process state (other tests may load the same EP library),
+// we copy the library to a temporary directory with a unique filename. This guarantees the copy
+// has never been loaded, so we can reliably detect refcount leaks via IsLibraryLoaded.
+TEST(OrtEpLibrary, RegisterUnregisterDoesNotLeakLibraryHandle) {
+  const std::filesystem::path& original_library_path = Utils::example_ep_info.library_path;
+
+  // Use a unique registration name to avoid conflicts with other tests that may have
+  // registered the same EP library and failed to unregister it.
+  const std::string registration_name = "handle_leak_test_ep";
+
+  // Copy the EP library to the temp directory with a unique filename so it is guaranteed to
+  // not already be loaded in this process.
+  TemporaryDirectory temp_dir(ORT_TSTR("test_handle_leak_temp"));
+  const std::filesystem::path temp_library_path =
+      std::filesystem::path(temp_dir.Path()) /
+      GetSharedLibraryFileName(ORT_TSTR("handle_leak_test_ep"));
+
+  std::error_code ec;
+  std::filesystem::copy_file(original_library_path, temp_library_path,
+                             std::filesystem::copy_options::overwrite_existing, ec);
+  ASSERT_FALSE(ec) << "Failed to copy EP library to temp directory: " << ec.message();
+
+  std::optional<bool> loaded_before = IsLibraryLoaded(temp_library_path);
+  if (!loaded_before.has_value()) {
+    GTEST_SKIP() << "Platform does not support querying loaded-library state.";
+  }
+
+  // The copy should not be loaded yet since we just created it with a unique name.
+  ASSERT_FALSE(*loaded_before) << "Freshly copied library should not already be loaded in the process.";
+
+  // Register the plugin EP library inside a smaller scope so that the gsl::finally cleanup
+  // calls UnregisterExecutionProviderLibrary exactly once when leaving the scope.
+  {
+    ASSERT_NO_THROW(ort_env->RegisterExecutionProviderLibrary(registration_name.c_str(), temp_library_path.c_str()));
+    auto cleanup_lib = gsl::finally([&registration_name] {
+      Ort::Status ignored{Ort::GetApi().UnregisterExecutionProviderLibrary(*ort_env, registration_name.c_str())};
+    });
+
+    // The library should be loaded now.
+    ASSERT_TRUE(IsLibraryLoaded(temp_library_path).value_or(false)) << "Library should be loaded after registration.";
+  }
+
+  // If the fix is applied, the library should be fully unloaded (refcount == 0).
+  // Without the fix, ProviderLibrary::Load() leaks a refcount so the library remains mapped.
+  EXPECT_FALSE(IsLibraryLoaded(temp_library_path).value_or(true))
+      << "Library handle leaked: EP library is still loaded after UnregisterExecutionProviderLibrary. "
+         "This indicates ProviderLibrary::Load() did not call Unload() on GetProvider symbol miss.";
+}
+
+}  // namespace test
+}  // namespace onnxruntime