text: //===-- asan_win_dynamic_runtime_thunk.cc ---------------------------------===//
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // 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$XIB", long, read)  // NOLINT
  #pragma section(".CRT$XID", long, read)  // NOLINT
  #pragma section(".CRT$XCAB", long, read)  // NOLINT
  #pragma section(".CRT$XTW", long, read)  // NOLINT
  #pragma section(".CRT$XTY", long, read)  // NOLINT
  #pragma section(".CRT$XLAB", long, read)  // NOLINT
  
  ////////////////////////////////////////////////////////////////////////////////
  // 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.cc).
  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
  