[SYCL] Only call shutdown when DLL is being unloaded, not when process is terminating

sycl/source/detail/global_handler.cpp

@@ -150,7 +150,8 @@ extern "C" __SYCL_EXPORT BOOL WINAPI DllMain(HINSTANCE hinstDLL,
   // Perform actions based on the reason for calling.
   switch (fdwReason) {
   case DLL_PROCESS_DETACH:
-    shutdown();
+    if (!lpReserved)
+      shutdown();
     break;
   case DLL_PROCESS_ATTACH:
   case DLL_THREAD_ATTACH:

sycl/unittests/CMakeLists.txt

@@ -24,3 +24,4 @@ add_subdirectory(thread_safety)
 add_subdirectory(program_manager)
 add_subdirectory(assert)
 add_subdirectory(Extensions)
+add_subdirectory(windows)

sycl/unittests/windows/CMakeLists.txt

@@ -0,0 +1,4 @@
+add_sycl_unittest(WindowsDllMainTest OBJECT
+  dllmain.cpp
+)
+

sycl/unittests/windows/dllmain.cpp

@@ -0,0 +1,65 @@
+//==----- dllmain.cpp --- verify behaviour of lib on process termination ---==//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+/*
+ * This test calls DllMain on Windows. This means, the process performs actions
+ * which are required for library unload. That said, the test requires to be a
+ * distinct binary executable.
+ */
+
+#include <CL/sycl.hpp>
+#include <helpers/CommonRedefinitions.hpp>
+#include <helpers/PiImage.hpp>
+#include <helpers/PiMock.hpp>
+
+#include <gtest/gtest.h>
+
+#ifdef _WIN32
+#include <windows.h>
+
+extern "C" BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason,
+                               LPVOID lpReserved);
+
+static std::atomic<int> TearDownCalls{0};
+
+pi_result redefinedTearDown(void *PluginParameter) {
+  fprintf(stderr, "intercepted tear down\n");
+  ++TearDownCalls;
+
+  return PI_SUCCESS;
+}
+#endif
+
+TEST(Windows, DllMainCall) {
+#ifdef _WIN32
+  sycl::platform Plt{sycl::default_selector()};
+  if (Plt.is_host()) {
+    printf("Test is not supported on host, skipping\n");
+    return;
+  }
+  sycl::unittest::PiMock Mock{Plt};
+  setupDefaultMockAPIs(Mock);
+  Mock.redefine<sycl::detail::PiApiKind::piTearDown>(redefinedTearDown);
+
+  // Teardown calls are only expected on sycl.dll library unload, not when
+  // process gets terminated.
+  // The first call to DllMain is to simulate library unload. The second one
+  // is to simulate process termination
+  fprintf(stderr, "Call DllMain for the first time\n");
+  DllMain((HINSTANCE)0, DLL_PROCESS_DETACH, (LPVOID)NULL);
+
+  int TearDownCallsDone = TearDownCalls.load();
+
+  EXPECT_NE(TearDownCallsDone, 0);
+
+  fprintf(stderr, "Call DllMain for the second time\n");
+  DllMain((HINSTANCE)0, DLL_PROCESS_DETACH, (LPVOID)0x01);
+
+  EXPECT_EQ(TearDownCalls.load(), TearDownCallsDone);
+#endif
+}