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diff --git a/lib/asan/asan_win_dynamic_runtime_thunk.cpp b/lib/asan/asan_win_dynamic_runtime_thunk.cpp
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index 000000000000..f0b5ec9eef7f
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+++ b/lib/asan/asan_win_dynamic_runtime_thunk.cpp
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+//===-- asan_win_dynamic_runtime_thunk.cpp --------------------------------===//
+//
+// 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 file is a part of AddressSanitizer, an address sanity checker.
+//
+// This file defines things that need to be present in the application modules
+// to interact with the ASan DLL runtime correctly and can't be implemented
+// using the default "import library" generated when linking the DLL RTL.
+//
+// This includes:
+//  - creating weak aliases to default implementation imported from asan dll.
+//  - forwarding the detect_stack_use_after_return runtime option
+//  - working around deficiencies of the MD runtime
+//  - installing a custom SEH handler
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef SANITIZER_DYNAMIC_RUNTIME_THUNK
+#define SANITIZER_IMPORT_INTERFACE 1
+#include "sanitizer_common/sanitizer_win_defs.h"
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+// Define weak alias for all weak functions imported from asan dll.
+#define INTERFACE_FUNCTION(Name)
+#define INTERFACE_WEAK_FUNCTION(Name) WIN_WEAK_IMPORT_DEF(Name)
+#include "asan_interface.inc"
+
+// First, declare CRT sections we'll be using in this file
+#pragma section(".CRT$XIB", long, read)
+#pragma section(".CRT$XID", long, read)
+#pragma section(".CRT$XCAB", long, read)
+#pragma section(".CRT$XTW", long, read)
+#pragma section(".CRT$XTY", long, read)
+#pragma section(".CRT$XLAB", long, read)
+
+////////////////////////////////////////////////////////////////////////////////
+// Define a copy of __asan_option_detect_stack_use_after_return that should be
+// used when linking an MD runtime with a set of object files on Windows.
+//
+// The ASan MD runtime dllexports '__asan_option_detect_stack_use_after_return',
+// so normally we would just dllimport it.  Unfortunately, the dllimport
+// attribute adds __imp_ prefix to the symbol name of a variable.
+// Since in general we don't know if a given TU is going to be used
+// with a MT or MD runtime and we don't want to use ugly __imp_ names on Windows
+// just to work around this issue, let's clone the variable that is constant
+// after initialization anyways.
+extern "C" {
+__declspec(dllimport) int __asan_should_detect_stack_use_after_return();
+int __asan_option_detect_stack_use_after_return;
+
+__declspec(dllimport) void* __asan_get_shadow_memory_dynamic_address();
+void* __asan_shadow_memory_dynamic_address;
+}
+
+static int InitializeClonedVariables() {
+  __asan_option_detect_stack_use_after_return =
+    __asan_should_detect_stack_use_after_return();
+  __asan_shadow_memory_dynamic_address =
+    __asan_get_shadow_memory_dynamic_address();
+  return 0;
+}
+
+static void NTAPI asan_thread_init(void *mod, unsigned long reason,
+    void *reserved) {
+  if (reason == DLL_PROCESS_ATTACH) InitializeClonedVariables();
+}
+
+// Our cloned variables must be initialized before C/C++ constructors.  If TLS
+// is used, our .CRT$XLAB initializer will run first. If not, our .CRT$XIB
+// initializer is needed as a backup.
+__declspec(allocate(".CRT$XIB")) int (*__asan_initialize_cloned_variables)() =
+    InitializeClonedVariables;
+__declspec(allocate(".CRT$XLAB")) void (NTAPI *__asan_tls_init)(void *,
+    unsigned long, void *) = asan_thread_init;
+
+////////////////////////////////////////////////////////////////////////////////
+// For some reason, the MD CRT doesn't call the C/C++ terminators during on DLL
+// unload or on exit.  ASan relies on LLVM global_dtors to call
+// __asan_unregister_globals on these events, which unfortunately doesn't work
+// with the MD runtime, see PR22545 for the details.
+// To work around this, for each DLL we schedule a call to UnregisterGlobals
+// using atexit() that calls a small subset of C terminators
+// where LLVM global_dtors is placed.  Fingers crossed, no other C terminators
+// are there.
+extern "C" int __cdecl atexit(void (__cdecl *f)(void));
+extern "C" void __cdecl _initterm(void *a, void *b);
+
+namespace {
+__declspec(allocate(".CRT$XTW")) void* before_global_dtors = 0;
+__declspec(allocate(".CRT$XTY")) void* after_global_dtors = 0;
+
+void UnregisterGlobals() {
+  _initterm(&before_global_dtors, &after_global_dtors);
+}
+
+int ScheduleUnregisterGlobals() {
+  return atexit(UnregisterGlobals);
+}
+}  // namespace
+
+// We need to call 'atexit(UnregisterGlobals);' as early as possible, but after
+// atexit() is initialized (.CRT$XIC).  As this is executed before C++
+// initializers (think ctors for globals), UnregisterGlobals gets executed after
+// dtors for C++ globals.
+__declspec(allocate(".CRT$XID"))
+int (*__asan_schedule_unregister_globals)() = ScheduleUnregisterGlobals;
+
+////////////////////////////////////////////////////////////////////////////////
+// ASan SEH handling.
+// We need to set the ASan-specific SEH handler at the end of CRT initialization
+// of each module (see also asan_win.cpp).
+extern "C" {
+__declspec(dllimport) int __asan_set_seh_filter();
+static int SetSEHFilter() { return __asan_set_seh_filter(); }
+
+// Unfortunately, putting a pointer to __asan_set_seh_filter into
+// __asan_intercept_seh gets optimized out, so we have to use an extra function.
+__declspec(allocate(".CRT$XCAB")) int (*__asan_seh_interceptor)() =
+    SetSEHFilter;
+}
+
+WIN_FORCE_LINK(__asan_dso_reg_hook)
+
+#endif // SANITIZER_DYNAMIC_RUNTIME_THUNK