text: // Copyright 2008, Google Inc.
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  
  #include "gtest/internal/gtest-port.h"
  
  #include <limits.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <cstdint>
  #include <fstream>
  #include <memory>
  
  #if GTEST_OS_WINDOWS
  # include <windows.h>
  # include <io.h>
  # include <sys/stat.h>
  # include <map>  // Used in ThreadLocal.
  # ifdef _MSC_VER
  #  include <crtdbg.h>
  # endif  // _MSC_VER
  #else
  # include <unistd.h>
  #endif  // GTEST_OS_WINDOWS
  
  #if GTEST_OS_MAC
  # include <mach/mach_init.h>
  # include <mach/task.h>
  # include <mach/vm_map.h>
  #endif  // GTEST_OS_MAC
  
  #if GTEST_OS_DRAGONFLY || GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD || \
      GTEST_OS_NETBSD || GTEST_OS_OPENBSD
  # include <sys/sysctl.h>
  # if GTEST_OS_DRAGONFLY || GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD
  #  include <sys/user.h>
  # endif
  #endif
  
  #if GTEST_OS_QNX
  # include <devctl.h>
  # include <fcntl.h>
  # include <sys/procfs.h>
  #endif  // GTEST_OS_QNX
  
  #if GTEST_OS_AIX
  # include <procinfo.h>
  # include <sys/types.h>
  #endif  // GTEST_OS_AIX
  
  #if GTEST_OS_FUCHSIA
  # include <zircon/process.h>
  # include <zircon/syscalls.h>
  #endif  // GTEST_OS_FUCHSIA
  
  #include "gtest/gtest-spi.h"
  #include "gtest/gtest-message.h"
  #include "gtest/internal/gtest-internal.h"
  #include "gtest/internal/gtest-string.h"
  #include "src/gtest-internal-inl.h"
  
  namespace testing {
  namespace internal {
  
  #if defined(_MSC_VER) || defined(__BORLANDC__)
  // MSVC and C++Builder do not provide a definition of STDERR_FILENO.
  const int kStdOutFileno = 1;
  const int kStdErrFileno = 2;
  #else
  const int kStdOutFileno = STDOUT_FILENO;
  const int kStdErrFileno = STDERR_FILENO;
  #endif  // _MSC_VER
  
  #if GTEST_OS_LINUX || GTEST_OS_GNU_HURD
  
  namespace {
  template <typename T>
  T ReadProcFileField(const std::string& filename, int field) {
    std::string dummy;
    std::ifstream file(filename.c_str());
    while (field-- > 0) {
      file >> dummy;
    }
    T output = 0;
    file >> output;
    return output;
  }
  }  // namespace
  
  // Returns the number of active threads, or 0 when there is an error.
  size_t GetThreadCount() {
    const std::string filename =
        (Message() << "/proc/" << getpid() << "/stat").GetString();
    return ReadProcFileField<size_t>(filename, 19);
  }
  
  #elif GTEST_OS_MAC
  
  size_t GetThreadCount() {
    const task_t task = mach_task_self();
    mach_msg_type_number_t thread_count;
    thread_act_array_t thread_list;
    const kern_return_t status = task_threads(task, &thread_list, &thread_count);
    if (status == KERN_SUCCESS) {
      // task_threads allocates resources in thread_list and we need to free them
      // to avoid leaks.
      vm_deallocate(task,
                    reinterpret_cast<vm_address_t>(thread_list),
                    sizeof(thread_t) * thread_count);
      return static_cast<size_t>(thread_count);
    } else {
      return 0;
    }
  }
  
  #elif GTEST_OS_DRAGONFLY || GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD || \
        GTEST_OS_NETBSD
  
  #if GTEST_OS_NETBSD
  #undef KERN_PROC
  #define KERN_PROC KERN_PROC2
  #define kinfo_proc kinfo_proc2
  #endif
  
  #if GTEST_OS_DRAGONFLY
  #define KP_NLWP(kp) (kp.kp_nthreads)
  #elif GTEST_OS_FREEBSD || GTEST_OS_GNU_KFREEBSD
  #define KP_NLWP(kp) (kp.ki_numthreads)
  #elif GTEST_OS_NETBSD
  #define KP_NLWP(kp) (kp.p_nlwps)
  #endif
  
  // Returns the number of threads running in the process, or 0 to indicate that
  // we cannot detect it.
  size_t GetThreadCount() {
    int mib[] = {
      CTL_KERN,
      KERN_PROC,
      KERN_PROC_PID,
      getpid(),
  #if GTEST_OS_NETBSD
      sizeof(struct kinfo_proc),
      1,
  #endif
    };
    u_int miblen = sizeof(mib) / sizeof(mib[0]);
    struct kinfo_proc info;
    size_t size = sizeof(info);
    if (sysctl(mib, miblen, &info, &size, NULL, 0)) {
      return 0;
    }
    return static_cast<size_t>(KP_NLWP(info));
  }
  #elif GTEST_OS_OPENBSD
  
  // Returns the number of threads running in the process, or 0 to indicate that
  // we cannot detect it.
  size_t GetThreadCount() {
    int mib[] = {
      CTL_KERN,
      KERN_PROC,
      KERN_PROC_PID | KERN_PROC_SHOW_THREADS,
      getpid(),
      sizeof(struct kinfo_proc),
      0,
    };
    u_int miblen = sizeof(mib) / sizeof(mib[0]);
  
    // get number of structs
    size_t size;
    if (sysctl(mib, miblen, NULL, &size, NULL, 0)) {
      return 0;
    }
  
    mib[5] = static_cast<int>(size / static_cast<size_t>(mib[4]));
  
    // populate array of structs
    struct kinfo_proc info[mib[5]];
    if (sysctl(mib, miblen, &info, &size, NULL, 0)) {
      return 0;
    }
  
    // exclude empty members
    size_t nthreads = 0;
    for (size_t i = 0; i < size / static_cast<size_t>(mib[4]); i++) {
      if (info[i].p_tid != -1)
        nthreads++;
    }
    return nthreads;
  }
  
  #elif GTEST_OS_QNX
  
  // Returns the number of threads running in the process, or 0 to indicate that
  // we cannot detect it.
  size_t GetThreadCount() {
    const int fd = open("/proc/self/as", O_RDONLY);
    if (fd < 0) {
      return 0;
    }
    procfs_info process_info;
    const int status =
        devctl(fd, DCMD_PROC_INFO, &process_info, sizeof(process_info), nullptr);
    close(fd);
    if (status == EOK) {
      return static_cast<size_t>(process_info.num_threads);
    } else {
      return 0;
    }
  }
  
  #elif GTEST_OS_AIX
  
  size_t GetThreadCount() {
    struct procentry64 entry;
    pid_t pid = getpid();
    int status = getprocs64(&entry, sizeof(entry), nullptr, 0, &pid, 1);
    if (status == 1) {
      return entry.pi_thcount;
    } else {
      return 0;
    }
  }
  
  #elif GTEST_OS_FUCHSIA
  
  size_t GetThreadCount() {
    int dummy_buffer;
    size_t avail;
    zx_status_t status = zx_object_get_info(
        zx_process_self(),
        ZX_INFO_PROCESS_THREADS,
        &dummy_buffer,
        0,
        nullptr,
        &avail);
    if (status == ZX_OK) {
      return avail;
    } else {
      return 0;
    }
  }
  
  #else
  
  size_t GetThreadCount() {
    // There's no portable way to detect the number of threads, so we just
    // return 0 to indicate that we cannot detect it.
    return 0;
  }
  
  #endif  // GTEST_OS_LINUX
  
  #if GTEST_IS_THREADSAFE && GTEST_OS_WINDOWS
  
  AutoHandle::AutoHandle()
      : handle_(INVALID_HANDLE_VALUE) {}
  
  AutoHandle::AutoHandle(Handle handle)
      : handle_(handle) {}
  
  AutoHandle::~AutoHandle() {
    Reset();
  }
  
  AutoHandle::Handle AutoHandle::Get() const {
    return handle_;
  }
  
  void AutoHandle::Reset() {
    Reset(INVALID_HANDLE_VALUE);
  }
  
  void AutoHandle::Reset(HANDLE handle) {
    // Resetting with the same handle we already own is invalid.
    if (handle_ != handle) {
      if (IsCloseable()) {
        ::CloseHandle(handle_);
      }
      handle_ = handle;
    } else {
      GTEST_CHECK_(!IsCloseable())
          << "Resetting a valid handle to itself is likely a programmer error "
              "and thus not allowed.";
    }
  }
  
  bool AutoHandle::IsCloseable() const {
    // Different Windows APIs may use either of these values to represent an
    // invalid handle.
    return handle_ != nullptr && handle_ != INVALID_HANDLE_VALUE;
  }
  
  Mutex::Mutex()
      : owner_thread_id_(0),
        type_(kDynamic),
        critical_section_init_phase_(0),
        critical_section_(new CRITICAL_SECTION) {
    ::InitializeCriticalSection(critical_section_);
  }
  
  Mutex::~Mutex() {
    // Static mutexes are leaked intentionally. It is not thread-safe to try
    // to clean them up.
    if (type_ == kDynamic) {
      ::DeleteCriticalSection(critical_section_);
      delete critical_section_;
      critical_section_ = nullptr;
    }
  }
  
  void Mutex::Lock() {
    ThreadSafeLazyInit();
    ::EnterCriticalSection(critical_section_);
    owner_thread_id_ = ::GetCurrentThreadId();
  }
  
  void Mutex::Unlock() {
    ThreadSafeLazyInit();
    // We don't protect writing to owner_thread_id_ here, as it's the
    // caller's responsibility to ensure that the current thread holds the
    // mutex when this is called.
    owner_thread_id_ = 0;
    ::LeaveCriticalSection(critical_section_);
  }
  
  // Does nothing if the current thread holds the mutex. Otherwise, crashes
  // with high probability.
  void Mutex::AssertHeld() {
    ThreadSafeLazyInit();
    GTEST_CHECK_(owner_thread_id_ == ::GetCurrentThreadId())
        << "The current thread is not holding the mutex @" << this;
  }
  
  namespace {
  
  #ifdef _MSC_VER
  // Use the RAII idiom to flag mem allocs that are intentionally never
  // deallocated. The motivation is to silence the false positive mem leaks
  // that are reported by the debug version of MS's CRT which can only detect
  // if an alloc is missing a matching deallocation.
  // Example:
  //    MemoryIsNotDeallocated memory_is_not_deallocated;
  //    critical_section_ = new CRITICAL_SECTION;
  //
  class MemoryIsNotDeallocated
  {
   public:
    MemoryIsNotDeallocated() : old_crtdbg_flag_(0) {
      old_crtdbg_flag_ = _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG);
      // Set heap allocation block type to _IGNORE_BLOCK so that MS debug CRT
      // doesn't report mem leak if there's no matching deallocation.
      (void)_CrtSetDbgFlag(old_crtdbg_flag_ & ~_CRTDBG_ALLOC_MEM_DF);
    }
  
    ~MemoryIsNotDeallocated() {
      // Restore the original _CRTDBG_ALLOC_MEM_DF flag
      (void)_CrtSetDbgFlag(old_crtdbg_flag_);
    }
  
   private:
    int old_crtdbg_flag_;
  
    GTEST_DISALLOW_COPY_AND_ASSIGN_(MemoryIsNotDeallocated);
  };
  #endif  // _MSC_VER
  
  }  // namespace
  
  // Initializes owner_thread_id_ and critical_section_ in static mutexes.
  void Mutex::ThreadSafeLazyInit() {
    // Dynamic mutexes are initialized in the constructor.
    if (type_ == kStatic) {
      switch (
          ::InterlockedCompareExchange(&critical_section_init_phase_, 1L, 0L)) {
        case 0:
          // If critical_section_init_phase_ was 0 before the exchange, we
          // are the first to test it and need to perform the initialization.
          owner_thread_id_ = 0;
          {
            // Use RAII to flag that following mem alloc is never deallocated.
  #ifdef _MSC_VER
            MemoryIsNotDeallocated memory_is_not_deallocated;
  #endif  // _MSC_VER
            critical_section_ = new CRITICAL_SECTION;
          }
          ::InitializeCriticalSection(critical_section_);
          // Updates the critical_section_init_phase_ to 2 to signal
          // initialization complete.
          GTEST_CHECK_(::InterlockedCompareExchange(
                            &critical_section_init_phase_, 2L, 1L) ==
                        1L);
          break;
        case 1:
          // Somebody else is already initializing the mutex; spin until they
          // are done.
          while (::InterlockedCompareExchange(&critical_section_init_phase_,
                                              2L,
                                              2L) != 2L) {
            // Possibly yields the rest of the thread's time slice to other
            // threads.
            ::Sleep(0);
          }
          break;
  
        case 2:
          break;  // The mutex is already initialized and ready for use.
  
        default:
          GTEST_CHECK_(false)
              << "Unexpected value of critical_section_init_phase_ "
              << "while initializing a static mutex.";
      }
    }
  }
  
  namespace {
  
  class ThreadWithParamSupport : public ThreadWithParamBase {
   public:
    static HANDLE CreateThread(Runnable* runnable,
                               Notification* thread_can_start) {
      ThreadMainParam* param = new ThreadMainParam(runnable, thread_can_start);
      DWORD thread_id;
      HANDLE thread_handle = ::CreateThread(
          nullptr,  // Default security.
          0,        // Default stack size.
          &ThreadWithParamSupport::ThreadMain,
          param,        // Parameter to ThreadMainStatic
          0x0,          // Default creation flags.
          &thread_id);  // Need a valid pointer for the call to work under Win98.
      GTEST_CHECK_(thread_handle != nullptr)
          << "CreateThread failed with error " << ::GetLastError() << ".";
      if (thread_handle == nullptr) {
        delete param;
      }
      return thread_handle;
    }
  
   private:
    struct ThreadMainParam {
      ThreadMainParam(Runnable* runnable, Notification* thread_can_start)
          : runnable_(runnable),
            thread_can_start_(thread_can_start) {
      }
      std::unique_ptr<Runnable> runnable_;
      // Does not own.
      Notification* thread_can_start_;
    };
  
    static DWORD WINAPI ThreadMain(void* ptr) {
      // Transfers ownership.
      std::unique_ptr<ThreadMainParam> param(static_cast<ThreadMainParam*>(ptr));
      if (param->thread_can_start_ != nullptr)
        param->thread_can_start_->WaitForNotification();
      param->runnable_->Run();
      return 0;
    }
  
    // Prohibit instantiation.
    ThreadWithParamSupport();
  
    GTEST_DISALLOW_COPY_AND_ASSIGN_(ThreadWithParamSupport);
  };
  
  }  // namespace
  
  ThreadWithParamBase::ThreadWithParamBase(Runnable *runnable,
                                           Notification* thread_can_start)
        : thread_(ThreadWithParamSupport::CreateThread(runnable,
                                                       thread_can_start)) {
  }
  
  ThreadWithParamBase::~ThreadWithParamBase() {
    Join();
  }
  
  void ThreadWithParamBase::Join() {
    GTEST_CHECK_(::WaitForSingleObject(thread_.Get(), INFINITE) == WAIT_OBJECT_0)
        << "Failed to join the thread with error " << ::GetLastError() << ".";
  }
  
  // Maps a thread to a set of ThreadIdToThreadLocals that have values
  // instantiated on that thread and notifies them when the thread exits.  A
  // ThreadLocal instance is expected to persist until all threads it has
  // values on have terminated.
  class ThreadLocalRegistryImpl {
   public:
    // Registers thread_local_instance as having value on the current thread.
    // Returns a value that can be used to identify the thread from other threads.
    static ThreadLocalValueHolderBase* GetValueOnCurrentThread(
        const ThreadLocalBase* thread_local_instance) {
  #ifdef _MSC_VER
      MemoryIsNotDeallocated memory_is_not_deallocated;
  #endif  // _MSC_VER
      DWORD current_thread = ::GetCurrentThreadId();
      MutexLock lock(&mutex_);
      ThreadIdToThreadLocals* const thread_to_thread_locals =
          GetThreadLocalsMapLocked();
      ThreadIdToThreadLocals::iterator thread_local_pos =
          thread_to_thread_locals->find(current_thread);
      if (thread_local_pos == thread_to_thread_locals->end()) {
        thread_local_pos = thread_to_thread_locals->insert(
            std::make_pair(current_thread, ThreadLocalValues())).first;
        StartWatcherThreadFor(current_thread);
      }
      ThreadLocalValues& thread_local_values = thread_local_pos->second;
      ThreadLocalValues::iterator value_pos =
          thread_local_values.find(thread_local_instance);
      if (value_pos == thread_local_values.end()) {
        value_pos =
            thread_local_values
                .insert(std::make_pair(
                    thread_local_instance,
                    std::shared_ptr<ThreadLocalValueHolderBase>(
                        thread_local_instance->NewValueForCurrentThread())))
                .first;
      }
      return value_pos->second.get();
    }
  
    static void OnThreadLocalDestroyed(
        const ThreadLocalBase* thread_local_instance) {
      std::vector<std::shared_ptr<ThreadLocalValueHolderBase> > value_holders;
      // Clean up the ThreadLocalValues data structure while holding the lock, but
      // defer the destruction of the ThreadLocalValueHolderBases.
      {
        MutexLock lock(&mutex_);
        ThreadIdToThreadLocals* const thread_to_thread_locals =
            GetThreadLocalsMapLocked();
        for (ThreadIdToThreadLocals::iterator it =
            thread_to_thread_locals->begin();
            it != thread_to_thread_locals->end();
            ++it) {
          ThreadLocalValues& thread_local_values = it->second;
          ThreadLocalValues::iterator value_pos =
              thread_local_values.find(thread_local_instance);
          if (value_pos != thread_local_values.end()) {
            value_holders.push_back(value_pos->second);
            thread_local_values.erase(value_pos);
            // This 'if' can only be successful at most once, so theoretically we
            // could break out of the loop here, but we don't bother doing so.
          }
        }
      }
      // Outside the lock, let the destructor for 'value_holders' deallocate the
      // ThreadLocalValueHolderBases.
    }
  
    static void OnThreadExit(DWORD thread_id) {
      GTEST_CHECK_(thread_id != 0) << ::GetLastError();
      std::vector<std::shared_ptr<ThreadLocalValueHolderBase> > value_holders;
      // Clean up the ThreadIdToThreadLocals data structure while holding the
      // lock, but defer the destruction of the ThreadLocalValueHolderBases.
      {
        MutexLock lock(&mutex_);
        ThreadIdToThreadLocals* const thread_to_thread_locals =
            GetThreadLocalsMapLocked();
        ThreadIdToThreadLocals::iterator thread_local_pos =
            thread_to_thread_locals->find(thread_id);
        if (thread_local_pos != thread_to_thread_locals->end()) {
          ThreadLocalValues& thread_local_values = thread_local_pos->second;
          for (ThreadLocalValues::iterator value_pos =
              thread_local_values.begin();
              value_pos != thread_local_values.end();
              ++value_pos) {
            value_holders.push_back(value_pos->second);
          }
          thread_to_thread_locals->erase(thread_local_pos);
        }
      }
      // Outside the lock, let the destructor for 'value_holders' deallocate the
      // ThreadLocalValueHolderBases.
    }
  
   private:
    // In a particular thread, maps a ThreadLocal object to its value.
    typedef std::map<const ThreadLocalBase*,
                     std::shared_ptr<ThreadLocalValueHolderBase> >
        ThreadLocalValues;
    // Stores all ThreadIdToThreadLocals having values in a thread, indexed by
    // thread's ID.
    typedef std::map<DWORD, ThreadLocalValues> ThreadIdToThreadLocals;
  
    // Holds the thread id and thread handle that we pass from
    // StartWatcherThreadFor to WatcherThreadFunc.
    typedef std::pair<DWORD, HANDLE> ThreadIdAndHandle;
  
    static void StartWatcherThreadFor(DWORD thread_id) {
      // The returned handle will be kept in thread_map and closed by
      // watcher_thread in WatcherThreadFunc.
      HANDLE thread = ::OpenThread(SYNCHRONIZE | THREAD_QUERY_INFORMATION,
                                   FALSE,
                                   thread_id);
      GTEST_CHECK_(thread != nullptr);
      // We need to pass a valid thread ID pointer into CreateThread for it
      // to work correctly under Win98.
      DWORD watcher_thread_id;
      HANDLE watcher_thread = ::CreateThread(
          nullptr,  // Default security.
          0,        // Default stack size
          &ThreadLocalRegistryImpl::WatcherThreadFunc,
          reinterpret_cast<LPVOID>(new ThreadIdAndHandle(thread_id, thread)),
          CREATE_SUSPENDED, &watcher_thread_id);
      GTEST_CHECK_(watcher_thread != nullptr)
          << "CreateThread failed with error " << ::GetLastError() << ".";
      // Give the watcher thread the same priority as ours to avoid being
      // blocked by it.
      ::SetThreadPriority(watcher_thread,
                          ::GetThreadPriority(::GetCurrentThread()));
      ::ResumeThread(watcher_thread);
      ::CloseHandle(watcher_thread);
    }
  
    // Monitors exit from a given thread and notifies those
    // ThreadIdToThreadLocals about thread termination.
    static DWORD WINAPI WatcherThreadFunc(LPVOID param) {
      const ThreadIdAndHandle* tah =
          reinterpret_cast<const ThreadIdAndHandle*>(param);
      GTEST_CHECK_(
          ::WaitForSingleObject(tah->second, INFINITE) == WAIT_OBJECT_0);
      OnThreadExit(tah->first);
      ::CloseHandle(tah->second);
      delete tah;
      return 0;
    }
  
    // Returns map of thread local instances.
    static ThreadIdToThreadLocals* GetThreadLocalsMapLocked() {
      mutex_.AssertHeld();
  #ifdef _MSC_VER
      MemoryIsNotDeallocated memory_is_not_deallocated;
  #endif  // _MSC_VER
      static ThreadIdToThreadLocals* map = new ThreadIdToThreadLocals();
      return map;
    }
  
    // Protects access to GetThreadLocalsMapLocked() and its return value.
    static Mutex mutex_;
    // Protects access to GetThreadMapLocked() and its return value.
    static Mutex thread_map_mutex_;
  };
  
  Mutex ThreadLocalRegistryImpl::mutex_(Mutex::kStaticMutex);  // NOLINT
  Mutex ThreadLocalRegistryImpl::thread_map_mutex_(Mutex::kStaticMutex);  // NOLINT
  
  ThreadLocalValueHolderBase* ThreadLocalRegistry::GetValueOnCurrentThread(
        const ThreadLocalBase* thread_local_instance) {
    return ThreadLocalRegistryImpl::GetValueOnCurrentThread(
        thread_local_instance);
  }
  
  void ThreadLocalRegistry::OnThreadLocalDestroyed(
        const ThreadLocalBase* thread_local_instance) {
    ThreadLocalRegistryImpl::OnThreadLocalDestroyed(thread_local_instance);
  }
  
  #endif  // GTEST_IS_THREADSAFE && GTEST_OS_WINDOWS
  
  #if GTEST_USES_POSIX_RE
  
  // Implements RE.  Currently only needed for death tests.
  
  RE::~RE() {
    if (is_valid_) {
      // regfree'ing an invalid regex might crash because the content
      // of the regex is undefined. Since the regex's are essentially
      // the same, one cannot be valid (or invalid) without the other
      // being so too.
      regfree(&partial_regex_);
      regfree(&full_regex_);
    }
    free(const_cast<char*>(pattern_));
  }
  
  // Returns true if and only if regular expression re matches the entire str.
  bool RE::FullMatch(const char* str, const RE& re) {
    if (!re.is_valid_) return false;
  
    regmatch_t match;
    return regexec(&re.full_regex_, str, 1, &match, 0) == 0;
  }
  
  // Returns true if and only if regular expression re matches a substring of
  // str (including str itself).
  bool RE::PartialMatch(const char* str, const RE& re) {
    if (!re.is_valid_) return false;
  
    regmatch_t match;
    return regexec(&re.partial_regex_, str, 1, &match, 0) == 0;
  }
  
  // Initializes an RE from its string representation.
  void RE::Init(const char* regex) {
    pattern_ = posix::StrDup(regex);
  
    // Reserves enough bytes to hold the regular expression used for a
    // full match.
    const size_t full_regex_len = strlen(regex) + 10;
    char* const full_pattern = new char[full_regex_len];
  
    snprintf(full_pattern, full_regex_len, "^(%s)$", regex);
    is_valid_ = regcomp(&full_regex_, full_pattern, REG_EXTENDED) == 0;
    // We want to call regcomp(&partial_regex_, ...) even if the
    // previous expression returns false.  Otherwise partial_regex_ may
    // not be properly initialized can may cause trouble when it's
    // freed.
    //
    // Some implementation of POSIX regex (e.g. on at least some
    // versions of Cygwin) doesn't accept the empty string as a valid
    // regex.  We change it to an equivalent form "()" to be safe.
    if (is_valid_) {
      const char* const partial_regex = (*regex == '\0') ? "()" : regex;
      is_valid_ = regcomp(&partial_regex_, partial_regex, REG_EXTENDED) == 0;
    }
    EXPECT_TRUE(is_valid_)
        << "Regular expression \"" << regex
        << "\" is not a valid POSIX Extended regular expression.";
  
    delete[] full_pattern;
  }
  
  #elif GTEST_USES_SIMPLE_RE
  
  // Returns true if and only if ch appears anywhere in str (excluding the
  // terminating '\0' character).
  bool IsInSet(char ch, const char* str) {
    return ch != '\0' && strchr(str, ch) != nullptr;
  }
  
  // Returns true if and only if ch belongs to the given classification.
  // Unlike similar functions in <ctype.h>, these aren't affected by the
  // current locale.
  bool IsAsciiDigit(char ch) { return '0' <= ch && ch <= '9'; }
  bool IsAsciiPunct(char ch) {
    return IsInSet(ch, "^-!\"#$%&'()*+,./:;<=>?@[\\]_`{|}~");
  }
  bool IsRepeat(char ch) { return IsInSet(ch, "?*+"); }
  bool IsAsciiWhiteSpace(char ch) { return IsInSet(ch, " \f\n\r\t\v"); }
  bool IsAsciiWordChar(char ch) {
    return ('a' <= ch && ch <= 'z') || ('A' <= ch && ch <= 'Z') ||
        ('0' <= ch && ch <= '9') || ch == '_';
  }
  
  // Returns true if and only if "\\c" is a supported escape sequence.
  bool IsValidEscape(char c) {
    return (IsAsciiPunct(c) || IsInSet(c, "dDfnrsStvwW"));
  }
  
  // Returns true if and only if the given atom (specified by escaped and
  // pattern) matches ch.  The result is undefined if the atom is invalid.
  bool AtomMatchesChar(bool escaped, char pattern_char, char ch) {
    if (escaped) {  // "\\p" where p is pattern_char.
      switch (pattern_char) {
        case 'd': return IsAsciiDigit(ch);
        case 'D': return !IsAsciiDigit(ch);
        case 'f': return ch == '\f';
        case 'n': return ch == '\n';
        case 'r': return ch == '\r';
        case 's': return IsAsciiWhiteSpace(ch);
        case 'S': return !IsAsciiWhiteSpace(ch);
        case 't': return ch == '\t';
        case 'v': return ch == '\v';
        case 'w': return IsAsciiWordChar(ch);
        case 'W': return !IsAsciiWordChar(ch);
      }
      return IsAsciiPunct(pattern_char) && pattern_char == ch;
    }
  
    return (pattern_char == '.' && ch != '\n') || pattern_char == ch;
  }
  
  // Helper function used by ValidateRegex() to format error messages.
  static std::string FormatRegexSyntaxError(const char* regex, int index) {
    return (Message() << "Syntax error at index " << index
            << " in simple regular expression \"" << regex << "\": ").GetString();
  }
  
  // Generates non-fatal failures and returns false if regex is invalid;
  // otherwise returns true.
  bool ValidateRegex(const char* regex) {
    if (regex == nullptr) {
      ADD_FAILURE() << "NULL is not a valid simple regular expression.";
      return false;
    }
  
    bool is_valid = true;
  
    // True if and only if ?, *, or + can follow the previous atom.
    bool prev_repeatable = false;
    for (int i = 0; regex[i]; i++) {
      if (regex[i] == '\\') {  // An escape sequence
        i++;
        if (regex[i] == '\0') {
          ADD_FAILURE() << FormatRegexSyntaxError(regex, i - 1)
                        << "'\\' cannot appear at the end.";
          return false;
        }
  
        if (!IsValidEscape(regex[i])) {
          ADD_FAILURE() << FormatRegexSyntaxError(regex, i - 1)
                        << "invalid escape sequence \"\\" << regex[i] << "\".";
          is_valid = false;
        }
        prev_repeatable = true;
      } else {  // Not an escape sequence.
        const char ch = regex[i];
  
        if (ch == '^' && i > 0) {
          ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
                        << "'^' can only appear at the beginning.";
          is_valid = false;
        } else if (ch == '$' && regex[i + 1] != '\0') {
          ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
                        << "'$' can only appear at the end.";
          is_valid = false;
        } else if (IsInSet(ch, "()[]{}|")) {
          ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
                        << "'" << ch << "' is unsupported.";
          is_valid = false;
        } else if (IsRepeat(ch) && !prev_repeatable) {
          ADD_FAILURE() << FormatRegexSyntaxError(regex, i)
                        << "'" << ch << "' can only follow a repeatable token.";
          is_valid = false;
        }
  
        prev_repeatable = !IsInSet(ch, "^$?*+");
      }
    }
  
    return is_valid;
  }
  
  // Matches a repeated regex atom followed by a valid simple regular
  // expression.  The regex atom is defined as c if escaped is false,
  // or \c otherwise.  repeat is the repetition meta character (?, *,
  // or +).  The behavior is undefined if str contains too many
  // characters to be indexable by size_t, in which case the test will
  // probably time out anyway.  We are fine with this limitation as
  // std::string has it too.
  bool MatchRepetitionAndRegexAtHead(
      bool escaped, char c, char repeat, const char* regex,
      const char* str) {
    const size_t min_count = (repeat == '+') ? 1 : 0;
    const size_t max_count = (repeat == '?') ? 1 :
        static_cast<size_t>(-1) - 1;
    // We cannot call numeric_limits::max() as it conflicts with the
    // max() macro on Windows.
  
    for (size_t i = 0; i <= max_count; ++i) {
      // We know that the atom matches each of the first i characters in str.
      if (i >= min_count && MatchRegexAtHead(regex, str + i)) {
        // We have enough matches at the head, and the tail matches too.
        // Since we only care about *whether* the pattern matches str
        // (as opposed to *how* it matches), there is no need to find a
        // greedy match.
        return true;
      }
      if (str[i] == '\0' || !AtomMatchesChar(escaped, c, str[i]))
        return false;
    }
    return false;
  }
  
  // Returns true if and only if regex matches a prefix of str. regex must
  // be a valid simple regular expression and not start with "^", or the
  // result is undefined.
  bool MatchRegexAtHead(const char* regex, const char* str) {
    if (*regex == '\0')  // An empty regex matches a prefix of anything.
      return true;
  
    // "$" only matches the end of a string.  Note that regex being
    // valid guarantees that there's nothing after "$" in it.
    if (*regex == '$')
      return *str == '\0';
  
    // Is the first thing in regex an escape sequence?
    const bool escaped = *regex == '\\';
    if (escaped)
      ++regex;
    if (IsRepeat(regex[1])) {
      // MatchRepetitionAndRegexAtHead() calls MatchRegexAtHead(), so
      // here's an indirect recursion.  It terminates as the regex gets
      // shorter in each recursion.
      return MatchRepetitionAndRegexAtHead(
          escaped, regex[0], regex[1], regex + 2, str);
    } else {
      // regex isn't empty, isn't "$", and doesn't start with a
      // repetition.  We match the first atom of regex with the first
      // character of str and recurse.
      return (*str != '\0') && AtomMatchesChar(escaped, *regex, *str) &&
          MatchRegexAtHead(regex + 1, str + 1);
    }
  }
  
  // Returns true if and only if regex matches any substring of str.  regex must
  // be a valid simple regular expression, or the result is undefined.
  //
  // The algorithm is recursive, but the recursion depth doesn't exceed
  // the regex length, so we won't need to worry about running out of
  // stack space normally.  In rare cases the time complexity can be
  // exponential with respect to the regex length + the string length,
  // but usually it's must faster (often close to linear).
  bool MatchRegexAnywhere(const char* regex, const char* str) {
    if (regex == nullptr || str == nullptr) return false;
  
    if (*regex == '^')
      return MatchRegexAtHead(regex + 1, str);
  
    // A successful match can be anywhere in str.
    do {
      if (MatchRegexAtHead(regex, str))
        return true;
    } while (*str++ != '\0');
    return false;
  }
  
  // Implements the RE class.
  
  RE::~RE() {
    free(const_cast<char*>(pattern_));
    free(const_cast<char*>(full_pattern_));
  }
  
  // Returns true if and only if regular expression re matches the entire str.
  bool RE::FullMatch(const char* str, const RE& re) {
    return re.is_valid_ && MatchRegexAnywhere(re.full_pattern_, str);
  }
  
  // Returns true if and only if regular expression re matches a substring of
  // str (including str itself).
  bool RE::PartialMatch(const char* str, const RE& re) {
    return re.is_valid_ && MatchRegexAnywhere(re.pattern_, str);
  }
  
  // Initializes an RE from its string representation.
  void RE::Init(const char* regex) {
    pattern_ = full_pattern_ = nullptr;
    if (regex != nullptr) {
      pattern_ = posix::StrDup(regex);
    }
  
    is_valid_ = ValidateRegex(regex);
    if (!is_valid_) {
      // No need to calculate the full pattern when the regex is invalid.
      return;
    }
  
    const size_t len = strlen(regex);
    // Reserves enough bytes to hold the regular expression used for a
    // full match: we need space to prepend a '^', append a '$', and
    // terminate the string with '\0'.
    char* buffer = static_cast<char*>(malloc(len + 3));
    full_pattern_ = buffer;
  
    if (*regex != '^')
      *buffer++ = '^';  // Makes sure full_pattern_ starts with '^'.
  
    // We don't use snprintf or strncpy, as they trigger a warning when
    // compiled with VC++ 8.0.
    memcpy(buffer, regex, len);
    buffer += len;
  
    if (len == 0 || regex[len - 1] != '$')
      *buffer++ = '$';  // Makes sure full_pattern_ ends with '$'.
  
    *buffer = '\0';
  }
  
  #endif  // GTEST_USES_POSIX_RE
  
  const char kUnknownFile[] = "unknown file";
  
  // Formats a source file path and a line number as they would appear
  // in an error message from the compiler used to compile this code.
  GTEST_API_ ::std::string FormatFileLocation(const char* file, int line) {
    const std::string file_name(file == nullptr ? kUnknownFile : file);
  
    if (line < 0) {
      return file_name + ":";
    }
  #ifdef _MSC_VER
    return file_name + "(" + StreamableToString(line) + "):";
  #else
    return file_name + ":" + StreamableToString(line) + ":";
  #endif  // _MSC_VER
  }
  
  // Formats a file location for compiler-independent XML output.
  // Although this function is not platform dependent, we put it next to
  // FormatFileLocation in order to contrast the two functions.
  // Note that FormatCompilerIndependentFileLocation() does NOT append colon
  // to the file location it produces, unlike FormatFileLocation().
  GTEST_API_ ::std::string FormatCompilerIndependentFileLocation(
      const char* file, int line) {
    const std::string file_name(file == nullptr ? kUnknownFile : file);
  
    if (line < 0)
      return file_name;
    else
      return file_name + ":" + StreamableToString(line);
  }
  
  GTestLog::GTestLog(GTestLogSeverity severity, const char* file, int line)
      : severity_(severity) {
    const char* const marker =
        severity == GTEST_INFO ?    "[  INFO ]" :
        severity == GTEST_WARNING ? "[WARNING]" :
        severity == GTEST_ERROR ?   "[ ERROR ]" : "[ FATAL ]";
    GetStream() << ::std::endl << marker << " "
                << FormatFileLocation(file, line).c_str() << ": ";
  }
  
  // Flushes the buffers and, if severity is GTEST_FATAL, aborts the program.
  GTestLog::~GTestLog() {
    GetStream() << ::std::endl;
    if (severity_ == GTEST_FATAL) {
      fflush(stderr);
      posix::Abort();
    }
  }
  
  // Disable Microsoft deprecation warnings for POSIX functions called from
  // this class (creat, dup, dup2, and close)
  GTEST_DISABLE_MSC_DEPRECATED_PUSH_()
  
  #if GTEST_HAS_STREAM_REDIRECTION
  
  // Object that captures an output stream (stdout/stderr).
  class CapturedStream {
   public:
    // The ctor redirects the stream to a temporary file.
    explicit CapturedStream(int fd) : fd_(fd), uncaptured_fd_(dup(fd)) {
  # if GTEST_OS_WINDOWS
      char temp_dir_path[MAX_PATH + 1] = { '\0' };  // NOLINT
      char temp_file_path[MAX_PATH + 1] = { '\0' };  // NOLINT
  
      ::GetTempPathA(sizeof(temp_dir_path), temp_dir_path);
      const UINT success = ::GetTempFileNameA(temp_dir_path,
                                              "gtest_redir",
                                              0,  // Generate unique file name.
                                              temp_file_path);
      GTEST_CHECK_(success != 0)
          << "Unable to create a temporary file in " << temp_dir_path;
      const int captured_fd = creat(temp_file_path, _S_IREAD | _S_IWRITE);
      GTEST_CHECK_(captured_fd != -1) << "Unable to open temporary file "
                                      << temp_file_path;
      filename_ = temp_file_path;
  # else
      // There's no guarantee that a test has write access to the current
      // directory, so we create the temporary file in a temporary directory.
      std::string name_template;
  
  #  if GTEST_OS_LINUX_ANDROID
      // Note: Android applications are expected to call the framework's
      // Context.getExternalStorageDirectory() method through JNI to get
      // the location of the world-writable SD Card directory. However,
      // this requires a Context handle, which cannot be retrieved
      // globally from native code. Doing so also precludes running the
      // code as part of a regular standalone executable, which doesn't
      // run in a Dalvik process (e.g. when running it through 'adb shell').
      //
      // The location /data/local/tmp is directly accessible from native code.
      // '/sdcard' and other variants cannot be relied on, as they are not
      // guaranteed to be mounted, or may have a delay in mounting.
      name_template = "/data/local/tmp/";
  #  elif GTEST_OS_IOS
      char user_temp_dir[PATH_MAX + 1];
  
      // Documented alternative to NSTemporaryDirectory() (for obtaining creating
      // a temporary directory) at
      // https://developer.apple.com/library/archive/documentation/Security/Conceptual/SecureCodingGuide/Articles/RaceConditions.html#//apple_ref/doc/uid/TP40002585-SW10
      //
      // _CS_DARWIN_USER_TEMP_DIR (as well as _CS_DARWIN_USER_CACHE_DIR) is not
      // documented in the confstr() man page at
      // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/confstr.3.html#//apple_ref/doc/man/3/confstr
      // but are still available, according to the WebKit patches at
      // https://trac.webkit.org/changeset/262004/webkit
      // https://trac.webkit.org/changeset/263705/webkit
      //
      // The confstr() implementation falls back to getenv("TMPDIR"). See
      // https://opensource.apple.com/source/Libc/Libc-1439.100.3/gen/confstr.c.auto.html
      ::confstr(_CS_DARWIN_USER_TEMP_DIR, user_temp_dir, sizeof(user_temp_dir));
  
      name_template = user_temp_dir;
      if (name_template.back() != GTEST_PATH_SEP_[0])
        name_template.push_back(GTEST_PATH_SEP_[0]);
  #  else
      name_template = "/tmp/";
  #  endif
      name_template.append("gtest_captured_stream.XXXXXX");
  
      // mkstemp() modifies the string bytes in place, and does not go beyond the
      // string's length. This results in well-defined behavior in C++17.
      //
      // The const_cast is needed below C++17. The constraints on std::string
      // implementations in C++11 and above make assumption behind the const_cast
      // fairly safe.
      const int captured_fd = ::mkstemp(const_cast<char*>(name_template.data()));
      if (captured_fd == -1) {
        GTEST_LOG_(WARNING)
            << "Failed to create tmp file " << name_template
            << " for test; does the test have access to the /tmp directory?";
      }
      filename_ = std::move(name_template);
  # endif  // GTEST_OS_WINDOWS
      fflush(nullptr);
      dup2(captured_fd, fd_);
      close(captured_fd);
    }
  
    ~CapturedStream() {
      remove(filename_.c_str());
    }
  
    std::string GetCapturedString() {
      if (uncaptured_fd_ != -1) {
        // Restores the original stream.
        fflush(nullptr);
        dup2(uncaptured_fd_, fd_);
        close(uncaptured_fd_);
        uncaptured_fd_ = -1;
      }
  
      FILE* const file = posix::FOpen(filename_.c_str(), "r");
      if (file == nullptr) {
        GTEST_LOG_(FATAL) << "Failed to open tmp file " << filename_
                          << " for capturing stream.";
      }
      const std::string content = ReadEntireFile(file);
      posix::FClose(file);
      return content;
    }
  
   private:
    const int fd_;  // A stream to capture.
    int uncaptured_fd_;
    // Name of the temporary file holding the stderr output.
    ::std::string filename_;
  
    GTEST_DISALLOW_COPY_AND_ASSIGN_(CapturedStream);
  };
  
  GTEST_DISABLE_MSC_DEPRECATED_POP_()
  
  static CapturedStream* g_captured_stderr = nullptr;
  static CapturedStream* g_captured_stdout = nullptr;
  
  // Starts capturing an output stream (stdout/stderr).
  static void CaptureStream(int fd, const char* stream_name,
                            CapturedStream** stream) {
    if (*stream != nullptr) {
      GTEST_LOG_(FATAL) << "Only one " << stream_name
                        << " capturer can exist at a time.";
    }
    *stream = new CapturedStream(fd);
  }
  
  // Stops capturing the output stream and returns the captured string.
  static std::string GetCapturedStream(CapturedStream** captured_stream) {
    const std::string content = (*captured_stream)->GetCapturedString();
  
    delete *captured_stream;
    *captured_stream = nullptr;
  
    return content;
  }
  
  // Starts capturing stdout.
  void CaptureStdout() {
    CaptureStream(kStdOutFileno, "stdout", &g_captured_stdout);
  }
  
  // Starts capturing stderr.
  void CaptureStderr() {
    CaptureStream(kStdErrFileno, "stderr", &g_captured_stderr);
  }
  
  // Stops capturing stdout and returns the captured string.
  std::string GetCapturedStdout() {
    return GetCapturedStream(&g_captured_stdout);
  }
  
  // Stops capturing stderr and returns the captured string.
  std::string GetCapturedStderr() {
    return GetCapturedStream(&g_captured_stderr);
  }
  
  #endif  // GTEST_HAS_STREAM_REDIRECTION
  
  
  
  
  
  size_t GetFileSize(FILE* file) {
    fseek(file, 0, SEEK_END);
    return static_cast<size_t>(ftell(file));
  }
  
  std::string ReadEntireFile(FILE* file) {
    const size_t file_size = GetFileSize(file);
    char* const buffer = new char[file_size];
  
    size_t bytes_last_read = 0;  // # of bytes read in the last fread()
    size_t bytes_read = 0;       // # of bytes read so far
  
    fseek(file, 0, SEEK_SET);
  
    // Keeps reading the file until we cannot read further or the
    // pre-determined file size is reached.
    do {
      bytes_last_read = fread(buffer+bytes_read, 1, file_size-bytes_read, file);
      bytes_read += bytes_last_read;
    } while (bytes_last_read > 0 && bytes_read < file_size);
  
    const std::string content(buffer, bytes_read);
    delete[] buffer;
  
    return content;
  }
  
  #if GTEST_HAS_DEATH_TEST
  static const std::vector<std::string>* g_injected_test_argvs =
      nullptr;  // Owned.
  
  std::vector<std::string> GetInjectableArgvs() {
    if (g_injected_test_argvs != nullptr) {
      return *g_injected_test_argvs;
    }
    return GetArgvs();
  }
  
  void SetInjectableArgvs(const std::vector<std::string>* new_argvs) {
    if (g_injected_test_argvs != new_argvs) delete g_injected_test_argvs;
    g_injected_test_argvs = new_argvs;
  }
  
  void SetInjectableArgvs(const std::vector<std::string>& new_argvs) {
    SetInjectableArgvs(
        new std::vector<std::string>(new_argvs.begin(), new_argvs.end()));
  }
  
  void ClearInjectableArgvs() {
    delete g_injected_test_argvs;
    g_injected_test_argvs = nullptr;
  }
  #endif  // GTEST_HAS_DEATH_TEST
  
  #if GTEST_OS_WINDOWS_MOBILE
  namespace posix {
  void Abort() {
    DebugBreak();
    TerminateProcess(GetCurrentProcess(), 1);
  }
  }  // namespace posix
  #endif  // GTEST_OS_WINDOWS_MOBILE
  
  // Returns the name of the environment variable corresponding to the
  // given flag.  For example, FlagToEnvVar("foo") will return
  // "GTEST_FOO" in the open-source version.
  static std::string FlagToEnvVar(const char* flag) {
    const std::string full_flag =
        (Message() << GTEST_FLAG_PREFIX_ << flag).GetString();
  
    Message env_var;
    for (size_t i = 0; i != full_flag.length(); i++) {
      env_var << ToUpper(full_flag.c_str()[i]);
    }
  
    return env_var.GetString();
  }
  
  // Parses 'str' for a 32-bit signed integer.  If successful, writes
  // the result to *value and returns true; otherwise leaves *value
  // unchanged and returns false.
  bool ParseInt32(const Message& src_text, const char* str, int32_t* value) {
    // Parses the environment variable as a decimal integer.
    char* end = nullptr;
    const long long_value = strtol(str, &end, 10);  // NOLINT
  
    // Has strtol() consumed all characters in the string?
    if (*end != '\0') {
      // No - an invalid character was encountered.
      Message msg;
      msg << "WARNING: " << src_text
          << " is expected to be a 32-bit integer, but actually"
          << " has value \"" << str << "\".\n";
      printf("%s", msg.GetString().c_str());
      fflush(stdout);
      return false;
    }
  
    // Is the parsed value in the range of an int32_t?
    const auto result = static_cast<int32_t>(long_value);
    if (long_value == LONG_MAX || long_value == LONG_MIN ||
        // The parsed value overflows as a long.  (strtol() returns
        // LONG_MAX or LONG_MIN when the input overflows.)
        result != long_value
        // The parsed value overflows as an int32_t.
        ) {
      Message msg;
      msg << "WARNING: " << src_text
          << " is expected to be a 32-bit integer, but actually"
          << " has value " << str << ", which overflows.\n";
      printf("%s", msg.GetString().c_str());
      fflush(stdout);
      return false;
    }
  
    *value = result;
    return true;
  }
  
  // Reads and returns the Boolean environment variable corresponding to
  // the given flag; if it's not set, returns default_value.
  //
  // The value is considered true if and only if it's not "0".
  bool BoolFromGTestEnv(const char* flag, bool default_value) {
  #if defined(GTEST_GET_BOOL_FROM_ENV_)
    return GTEST_GET_BOOL_FROM_ENV_(flag, default_value);
  #else
    const std::string env_var = FlagToEnvVar(flag);
    const char* const string_value = posix::GetEnv(env_var.c_str());
    return string_value == nullptr ? default_value
                                   : strcmp(string_value, "0") != 0;
  #endif  // defined(GTEST_GET_BOOL_FROM_ENV_)
  }
  
  // Reads and returns a 32-bit integer stored in the environment
  // variable corresponding to the given flag; if it isn't set or
  // doesn't represent a valid 32-bit integer, returns default_value.
  int32_t Int32FromGTestEnv(const char* flag, int32_t default_value) {
  #if defined(GTEST_GET_INT32_FROM_ENV_)
    return GTEST_GET_INT32_FROM_ENV_(flag, default_value);
  #else
    const std::string env_var = FlagToEnvVar(flag);
    const char* const string_value = posix::GetEnv(env_var.c_str());
    if (string_value == nullptr) {
      // The environment variable is not set.
      return default_value;
    }
  
    int32_t result = default_value;
    if (!ParseInt32(Message() << "Environment variable " << env_var,
                    string_value, &result)) {
      printf("The default value %s is used.\n",
             (Message() << default_value).GetString().c_str());
      fflush(stdout);
      return default_value;
    }
  
    return result;
  #endif  // defined(GTEST_GET_INT32_FROM_ENV_)
  }
  
  // As a special case for the 'output' flag, if GTEST_OUTPUT is not
  // set, we look for XML_OUTPUT_FILE, which is set by the Bazel build
  // system.  The value of XML_OUTPUT_FILE is a filename without the
  // "xml:" prefix of GTEST_OUTPUT.
  // Note that this is meant to be called at the call site so it does
  // not check that the flag is 'output'
  // In essence this checks an env variable called XML_OUTPUT_FILE
  // and if it is set we prepend "xml:" to its value, if it not set we return ""
  std::string OutputFlagAlsoCheckEnvVar(){
    std::string default_value_for_output_flag = "";
    const char* xml_output_file_env = posix::GetEnv("XML_OUTPUT_FILE");
    if (nullptr != xml_output_file_env) {
      default_value_for_output_flag = std::string("xml:") + xml_output_file_env;
    }
    return default_value_for_output_flag;
  }
  
  // Reads and returns the string environment variable corresponding to
  // the given flag; if it's not set, returns default_value.
  const char* StringFromGTestEnv(const char* flag, const char* default_value) {
  #if defined(GTEST_GET_STRING_FROM_ENV_)
    return GTEST_GET_STRING_FROM_ENV_(flag, default_value);
  #else
    const std::string env_var = FlagToEnvVar(flag);
    const char* const value = posix::GetEnv(env_var.c_str());
    return value == nullptr ? default_value : value;
  #endif  // defined(GTEST_GET_STRING_FROM_ENV_)
  }
  
  }  // namespace internal
  }  // namespace testing
  