process_win.cc

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "platform/globals.h"
#if defined(DART_HOST_OS_WINDOWS)

#include "bin/process.h"

#include <process.h>  // NOLINT
#include <psapi.h>    // NOLINT
#include <vector>

#include "bin/builtin.h"
#include "bin/dartutils.h"
#include "bin/eventhandler.h"
#include "bin/lockers.h"
#include "bin/socket.h"
#include "bin/thread.h"
#include "bin/utils.h"
#include "bin/utils_win.h"
#include "platform/syslog.h"
#include "platform/text_buffer.h"

namespace dart {
namespace bin {

static constexpr int kReadHandle = 0;
static constexpr int kWriteHandle = 1;

int Process::global_exit_code_ = 0;
Mutex* Process::global_exit_code_mutex_ = nullptr;
Process::ExitHook Process::exit_hook_ = nullptr;

// ProcessInfo is used to map a process id to the process handle,
// wait handle for registered exit code event and the pipe used to
// communicate the exit code of the process to Dart.
// ProcessInfo objects are kept in the static singly-linked
// ProcessInfoList.
class ProcessInfo {
 public:
  ProcessInfo(DWORD process_id,
              HANDLE process_handle,
              HANDLE wait_handle,
              HANDLE exit_pipe)
      : process_id_(process_id),
        process_handle_(process_handle),
        wait_handle_(wait_handle),
        exit_pipe_(exit_pipe) {}

  ~ProcessInfo() {
    BOOL success = CloseHandle(process_handle_);
    if (!success) {
      FATAL("Failed to close process handle");
    }
    success = CloseHandle(exit_pipe_);
    if (!success) {
      FATAL("Failed to close process exit code pipe");
    }
  }

  DWORD pid() { return process_id_; }
  HANDLE process_handle() { return process_handle_; }
  HANDLE wait_handle() { return wait_handle_; }
  HANDLE exit_pipe() { return exit_pipe_; }
  ProcessInfo* next() { return next_; }
  void set_next(ProcessInfo* next) { next_ = next; }

 private:
  // Process id.
  DWORD process_id_;
  // Process handle.
  HANDLE process_handle_;
  // Wait handle identifying the exit-code wait operation registered
  // with RegisterWaitForSingleObject.
  HANDLE wait_handle_;
  // File descriptor for pipe to report exit code.
  HANDLE exit_pipe_;
  // Link to next ProcessInfo object in the singly-linked list.
  ProcessInfo* next_;

  DISALLOW_COPY_AND_ASSIGN(ProcessInfo);
};

// Singly-linked list of ProcessInfo objects for all active processes
// started from Dart.
class ProcessInfoList {
 public:
  static void Init();
  static void Cleanup();

  static void AddProcess(DWORD pid, HANDLE handle, HANDLE pipe) {
    // Register a callback to extract the exit code, when the process
    // is signaled.  The callback runs in a independent thread from the OS pool.
    // Because the callback depends on the process list containing
    // the process, lock the mutex until the process is added to the list.
    MutexLocker locker(mutex_);
    HANDLE wait_handle = INVALID_HANDLE_VALUE;
    BOOL success = RegisterWaitForSingleObject(
        &wait_handle, handle, &ExitCodeCallback, reinterpret_cast<PVOID>(pid),
        INFINITE, WT_EXECUTEONLYONCE);
    if (!success) {
      FATAL("Failed to register exit code wait operation.");
    }
    ProcessInfo* info = new ProcessInfo(pid, handle, wait_handle, pipe);
    // Mutate the process list under the mutex.
    info->set_next(active_processes_);
    active_processes_ = info;
  }

  static bool LookupProcess(DWORD pid,
                            HANDLE* handle,
                            HANDLE* wait_handle,
                            HANDLE* pipe) {
    MutexLocker locker(mutex_);
    ProcessInfo* current = active_processes_;
    while (current != nullptr) {
      if (current->pid() == pid) {
        *handle = current->process_handle();
        *wait_handle = current->wait_handle();
        *pipe = current->exit_pipe();
        return true;
      }
      current = current->next();
    }
    return false;
  }

  static void RemoveProcess(DWORD pid) {
    MutexLocker locker(mutex_);
    ProcessInfo* prev = nullptr;
    ProcessInfo* current = active_processes_;
    while (current != nullptr) {
      if (current->pid() == pid) {
        if (prev == nullptr) {
          active_processes_ = current->next();
        } else {
          prev->set_next(current->next());
        }
        delete current;
        return;
      }
      prev = current;
      current = current->next();
    }
  }

 private:
  // Callback called when an exit code is available from one of the
  // processes in the list.
  static void CALLBACK ExitCodeCallback(PVOID data, BOOLEAN timed_out) {
    if (timed_out) {
      return;
    }
    DWORD pid = reinterpret_cast<UINT_PTR>(data);
    HANDLE handle;
    HANDLE wait_handle;
    HANDLE exit_pipe;
    bool success = LookupProcess(pid, &handle, &wait_handle, &exit_pipe);
    if (!success) {
      FATAL("Failed to lookup process in list of active processes");
    }
    // Unregister the event in a non-blocking way.
    BOOL ok = UnregisterWait(wait_handle);
    if (!ok && (GetLastError() != ERROR_IO_PENDING)) {
      FATAL("Failed unregistering wait operation");
    }
    // Get and report the exit code to Dart.
    int exit_code;
    ok = GetExitCodeProcess(handle, reinterpret_cast<DWORD*>(&exit_code));
    if (!ok) {
      FATAL("GetExitCodeProcess failed %d\n", GetLastError());
    }
    int negative = 0;
    if (exit_code < 0) {
      exit_code = abs(exit_code);
      negative = 1;
    }
    int message[2] = {exit_code, negative};
    DWORD written;
    ok = WriteFile(exit_pipe, message, sizeof(message), &written, nullptr);
    // If the process has been closed, the read end of the exit
    // pipe has been closed. It is therefore not a problem that
    // WriteFile fails with a closed pipe error
    // (ERROR_NO_DATA). Other errors should not happen.
    if (ok && (written != sizeof(message))) {
      FATAL("Failed to write entire process exit message");
    } else if (!ok && (GetLastError() != ERROR_NO_DATA)) {
      FATAL("Failed to write exit code: %d", GetLastError());
    }
    // Remove the process from the list of active processes.
    RemoveProcess(pid);
  }

  // Linked list of ProcessInfo objects for all active processes
  // started from Dart code.
  static ProcessInfo* active_processes_;
  // Mutex protecting all accesses to the linked list of active
  // processes.
  static Mutex* mutex_;

  DISALLOW_ALLOCATION();
  DISALLOW_IMPLICIT_CONSTRUCTORS(ProcessInfoList);
};

ProcessInfo* ProcessInfoList::active_processes_ = nullptr;
Mutex* ProcessInfoList::mutex_ = nullptr;

// Types of pipes to create.
enum NamedPipeType { kInheritRead, kInheritWrite, kInheritNone };

// Create a pipe for communicating with a new process. The handles array
// will contain the read and write ends of the pipe. Based on the type
// one of the handles will be inheritable.
// NOTE: If this function returns false the handles might have been allocated
// and the caller should make sure to close them in case of an error.
static bool CreateProcessPipe(HANDLE handles[2],
                              wchar_t* pipe_name,
                              NamedPipeType type) {
  // Security attributes describing an inheritable handle.
  SECURITY_ATTRIBUTES inherit_handle;
  inherit_handle.nLength = sizeof(SECURITY_ATTRIBUTES);
  inherit_handle.bInheritHandle = TRUE;
  inherit_handle.lpSecurityDescriptor = nullptr;

  if (type == kInheritRead) {
    handles[kWriteHandle] =
        CreateNamedPipeW(pipe_name, PIPE_ACCESS_OUTBOUND | FILE_FLAG_OVERLAPPED,
                         PIPE_TYPE_BYTE | PIPE_WAIT,
                         1,     // Number of pipes
                         1024,  // Out buffer size
                         1024,  // In buffer size
                         0,     // Timeout in ms
                         nullptr);

    if (handles[kWriteHandle] == INVALID_HANDLE_VALUE) {
      Syslog::PrintErr("CreateNamedPipe failed %d\n", GetLastError());
      return false;
    }

    handles[kReadHandle] =
        CreateFileW(pipe_name, GENERIC_READ, 0, &inherit_handle, OPEN_EXISTING,
                    FILE_READ_ATTRIBUTES | FILE_FLAG_OVERLAPPED, nullptr);
    if (handles[kReadHandle] == INVALID_HANDLE_VALUE) {
      Syslog::PrintErr("CreateFile failed %d\n", GetLastError());
      return false;
    }
  } else {
    ASSERT((type == kInheritWrite) || (type == kInheritNone));
    handles[kReadHandle] =
        CreateNamedPipeW(pipe_name, PIPE_ACCESS_INBOUND | FILE_FLAG_OVERLAPPED,
                         PIPE_TYPE_BYTE | PIPE_WAIT,
                         1,     // Number of pipes
                         1024,  // Out buffer size
                         1024,  // In buffer size
                         0,     // Timeout in ms
                         nullptr);

    if (handles[kReadHandle] == INVALID_HANDLE_VALUE) {
      Syslog::PrintErr("CreateNamedPipe failed %d\n", GetLastError());
      return false;
    }

    handles[kWriteHandle] = CreateFileW(
        pipe_name, GENERIC_WRITE, 0,
        (type == kInheritWrite) ? &inherit_handle : nullptr, OPEN_EXISTING,
        FILE_WRITE_ATTRIBUTES | FILE_FLAG_OVERLAPPED, nullptr);
    if (handles[kWriteHandle] == INVALID_HANDLE_VALUE) {
      Syslog::PrintErr("CreateFile failed %d\n", GetLastError());
      return false;
    }
  }
  return true;
}

static void CloseProcessPipe(HANDLE handles[2]) {
  for (int i = kReadHandle; i < kWriteHandle; i++) {
    if (handles[i] != INVALID_HANDLE_VALUE) {
      if (!CloseHandle(handles[i])) {
        Syslog::PrintErr("CloseHandle failed %d\n", GetLastError());
      }
      handles[i] = INVALID_HANDLE_VALUE;
    }
  }
}

static void CloseProcessPipes(HANDLE handles1[2],
                              HANDLE handles2[2],
                              HANDLE handles3[2],
                              HANDLE handles4[2]) {
  CloseProcessPipe(handles1);
  CloseProcessPipe(handles2);
  CloseProcessPipe(handles3);
  CloseProcessPipe(handles4);
}

static int SetOsErrorMessage(char** os_error_message) {
  int error_code = GetLastError();
  const int kMaxMessageLength = 256;
  wchar_t message[kMaxMessageLength];
  FormatMessageIntoBuffer(error_code, message, kMaxMessageLength);
  *os_error_message = StringUtilsWin::WideToUtf8(message);
  return error_code;
}

// Open an inheritable handle to NUL.
static HANDLE OpenNul() {
  SECURITY_ATTRIBUTES inherit_handle;
  inherit_handle.nLength = sizeof(SECURITY_ATTRIBUTES);
  inherit_handle.bInheritHandle = TRUE;
  inherit_handle.lpSecurityDescriptor = nullptr;
  HANDLE nul = CreateFile(L"NUL", GENERIC_READ | GENERIC_WRITE, 0,
                          &inherit_handle, OPEN_EXISTING, 0, nullptr);
  if (nul == INVALID_HANDLE_VALUE) {
    Syslog::PrintErr("CloseHandle failed %d\n", GetLastError());
  }
  return nul;
}

const int kMaxPipeNameSize = 80;
template <int Count>
static int GenerateNames(wchar_t pipe_names[Count][kMaxPipeNameSize]) {
  UUID uuid;
  RPC_STATUS status = UuidCreateSequential(&uuid);
  if ((status != RPC_S_OK) && (status != RPC_S_UUID_LOCAL_ONLY)) {
    return status;
  }
  RPC_WSTR uuid_string;
  status = UuidToStringW(&uuid, &uuid_string);
  if (status != RPC_S_OK) {
    return status;
  }
  for (int i = 0; i < Count; i++) {
    static const wchar_t* prefix = L"\\\\.\\Pipe\\dart";
    _snwprintf(pipe_names[i], kMaxPipeNameSize, L"%s_%s_%d", prefix,
               uuid_string, i + 1);
  }
  status = RpcStringFreeW(&uuid_string);
  if (status != RPC_S_OK) {
    return status;
  }
  return 0;
}

class ProcessStarter {
 public:
  ProcessStarter(const char* path,
                 const char* arguments[],
                 intptr_t arguments_length,
                 const char* working_directory,
                 char* environment[],
                 intptr_t environment_length,
                 ProcessStartMode mode,
                 intptr_t* in,
                 intptr_t* out,
                 intptr_t* err,
                 intptr_t* id,
                 intptr_t* exit_handler,
                 char** os_error_message)
      : path_(path),
        working_directory_(working_directory),
        mode_(mode),
        in_(in),
        out_(out),
        err_(err),
        id_(id),
        exit_handler_(exit_handler),
        os_error_message_(os_error_message) {
    stdin_handles_[kReadHandle] = INVALID_HANDLE_VALUE;
    stdin_handles_[kWriteHandle] = INVALID_HANDLE_VALUE;
    stdout_handles_[kReadHandle] = INVALID_HANDLE_VALUE;
    stdout_handles_[kWriteHandle] = INVALID_HANDLE_VALUE;
    stderr_handles_[kReadHandle] = INVALID_HANDLE_VALUE;
    stderr_handles_[kWriteHandle] = INVALID_HANDLE_VALUE;
    exit_handles_[kReadHandle] = INVALID_HANDLE_VALUE;
    exit_handles_[kWriteHandle] = INVALID_HANDLE_VALUE;
    child_process_handle_ = INVALID_HANDLE_VALUE;

    // Transform input strings to system format.
    const wchar_t* system_path = StringUtilsWin::Utf8ToWide(path_);
    const wchar_t** system_arguments;
    system_arguments = reinterpret_cast<const wchar_t**>(
        Dart_ScopeAllocate(arguments_length * sizeof(*system_arguments)));
    for (int i = 0; i < arguments_length; i++) {
      system_arguments[i] = StringUtilsWin::Utf8ToWide(arguments[i]);
    }

    // Compute command-line length.
    int command_line_length = wcslen(system_path);
    for (int i = 0; i < arguments_length; i++) {
      command_line_length += wcslen(system_arguments[i]);
    }
    // Account for null termination and one space per argument.
    command_line_length += arguments_length + 1;

    // Put together command-line string.
    command_line_ = reinterpret_cast<wchar_t*>(
        Dart_ScopeAllocate(command_line_length * sizeof(*command_line_)));
    int len = 0;
    int remaining = command_line_length;
    int written =
        _snwprintf(command_line_ + len, remaining, L"%s", system_path);
    len += written;
    remaining -= written;
    ASSERT(remaining >= 0);
    for (int i = 0; i < arguments_length; i++) {
      written = _snwprintf(command_line_ + len, remaining, L" %s",
                           system_arguments[i]);
      len += written;
      remaining -= written;
      ASSERT(remaining >= 0);
    }

    // Create environment block if an environment is supplied.
    environment_block_ = nullptr;
    if (environment != nullptr) {
      wchar_t** system_environment;
      system_environment = reinterpret_cast<wchar_t**>(
          Dart_ScopeAllocate(environment_length * sizeof(*system_environment)));
      // Convert environment strings to system strings.
      for (intptr_t i = 0; i < environment_length; i++) {
        system_environment[i] = StringUtilsWin::Utf8ToWide(environment[i]);
      }

      // An environment block is a sequence of zero-terminated strings
      // followed by a block-terminating zero char.
      intptr_t block_size = 1;
      for (intptr_t i = 0; i < environment_length; i++) {
        block_size += wcslen(system_environment[i]) + 1;
      }
      environment_block_ = reinterpret_cast<wchar_t*>(
          Dart_ScopeAllocate(block_size * sizeof(*environment_block_)));
      intptr_t block_index = 0;
      for (intptr_t i = 0; i < environment_length; i++) {
        intptr_t len = wcslen(system_environment[i]);
        intptr_t result = _snwprintf(environment_block_ + block_index, len,
                                     L"%s", system_environment[i]);
        ASSERT(result == len);
        block_index += len;
        environment_block_[block_index++] = '\0';
      }
      // Block-terminating zero char.
      environment_block_[block_index++] = '\0';
      ASSERT(block_index == block_size);
    }

    system_working_directory_ = nullptr;
    if (working_directory_ != nullptr) {
      system_working_directory_ =
          StringUtilsWin::Utf8ToWide(working_directory_);
    }

    attribute_list_ = nullptr;
  }

  ~ProcessStarter() {
    if (attribute_list_ != nullptr) {
      DeleteProcThreadAttributeList(attribute_list_);
    }
  }

  int Start() {
    // Create pipes required.
    int err = CreatePipes();
    if (err != 0) {
      return err;
    }

    // Setup info structures.
    STARTUPINFOEXW startup_info;
    ZeroMemory(&startup_info, sizeof(startup_info));
    startup_info.StartupInfo.cb = sizeof(startup_info);
    if (mode_ != kInheritStdio) {
      startup_info.StartupInfo.hStdInput = stdin_handles_[kReadHandle];
      startup_info.StartupInfo.hStdOutput = stdout_handles_[kWriteHandle];
      startup_info.StartupInfo.hStdError = stderr_handles_[kWriteHandle];
      startup_info.StartupInfo.dwFlags = STARTF_USESTDHANDLES;

      // Setup the handles to inherit. We only want to inherit the three
      // handles for stdin, stdout and stderr.
      SIZE_T size = 0;
      // The call to determine the size of an attribute list always fails with
      // ERROR_INSUFFICIENT_BUFFER and that error should be ignored.
      if (!InitializeProcThreadAttributeList(nullptr, 1, 0, &size) &&
          (GetLastError() != ERROR_INSUFFICIENT_BUFFER)) {
        return CleanupAndReturnError();
      }
      attribute_list_ = reinterpret_cast<LPPROC_THREAD_ATTRIBUTE_LIST>(
          Dart_ScopeAllocate(size));
      ZeroMemory(attribute_list_, size);
      if (!InitializeProcThreadAttributeList(attribute_list_, 1, 0, &size)) {
        return CleanupAndReturnError();
      }
      inherited_handles_ = {stdin_handles_[kReadHandle],
                            stdout_handles_[kWriteHandle],
                            stderr_handles_[kWriteHandle]};
      if (!UpdateProcThreadAttribute(
              attribute_list_, 0, PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
              inherited_handles_.data(),
              inherited_handles_.size() * sizeof(HANDLE), nullptr, nullptr)) {
        return CleanupAndReturnError();
      }
      startup_info.lpAttributeList = attribute_list_;
    }

    PROCESS_INFORMATION process_info;
    ZeroMemory(&process_info, sizeof(process_info));

    // Create process.
    DWORD creation_flags =
        EXTENDED_STARTUPINFO_PRESENT | CREATE_UNICODE_ENVIRONMENT;
    if (!Process::ModeIsAttached(mode_)) {
      creation_flags |= DETACHED_PROCESS;
    } else {
      // Unless we are inheriting stdio which means there is some console
      // associated with the app, we want to ensure no console window pops
      // up for the spawned child.
      if (mode_ != kInheritStdio) {
        // Normally stdout for console dart application is associated with a
        // console that is launched from, but for gui applications(flutter on
        // windows) console might be absent, will be created by CreateProcessW
        // below. When that happens we ensure that console window doesn't
        // pop up.
        creation_flags |= CREATE_NO_WINDOW;
      }
    }
    BOOL result = CreateProcessW(
        nullptr,  // ApplicationName
        command_line_,
        nullptr,  // ProcessAttributes
        nullptr,  // ThreadAttributes
        TRUE,     // InheritHandles
        creation_flags, environment_block_, system_working_directory_,
        reinterpret_cast<STARTUPINFOW*>(&startup_info), &process_info);

    if (result == 0) {
      return CleanupAndReturnError();
    }

    if (mode_ != kInheritStdio) {
      CloseHandle(stdin_handles_[kReadHandle]);
      CloseHandle(stdout_handles_[kWriteHandle]);
      CloseHandle(stderr_handles_[kWriteHandle]);
    }
    if (Process::ModeIsAttached(mode_)) {
      ProcessInfoList::AddProcess(process_info.dwProcessId,
                                  process_info.hProcess,
                                  exit_handles_[kWriteHandle]);
    }
    if (mode_ != kDetached) {
      // Connect the three stdio streams.
      if (Process::ModeHasStdio(mode_)) {
        FileHandle* stdin_handle = new FileHandle(stdin_handles_[kWriteHandle]);
        FileHandle* stdout_handle =
            new FileHandle(stdout_handles_[kReadHandle]);
        FileHandle* stderr_handle =
            new FileHandle(stderr_handles_[kReadHandle]);
        *in_ = reinterpret_cast<intptr_t>(stdout_handle);
        *out_ = reinterpret_cast<intptr_t>(stdin_handle);
        *err_ = reinterpret_cast<intptr_t>(stderr_handle);
      }
      if (Process::ModeIsAttached(mode_)) {
        FileHandle* exit_handle = new FileHandle(exit_handles_[kReadHandle]);
        *exit_handler_ = reinterpret_cast<intptr_t>(exit_handle);
      }
    }
    child_process_handle_ = process_info.hProcess;
    CloseHandle(process_info.hThread);

    // Return process id.
    *id_ = process_info.dwProcessId;
    return 0;
  }

  int StartForExec() {
    ASSERT(mode_ == kInheritStdio);
    ASSERT(Process::ModeIsAttached(mode_));
    ASSERT(!Process::ModeHasStdio(mode_));

    // Setup info
    STARTUPINFOEXW startup_info;
    ZeroMemory(&startup_info, sizeof(startup_info));
    startup_info.StartupInfo.cb = sizeof(startup_info);

    // Setup the handles to inherit. We only want to inherit the three
    // handles for stdin, stdout and stderr.
    HANDLE stdin_handle = GetStdHandle(STD_INPUT_HANDLE);
    HANDLE stdout_handle = GetStdHandle(STD_OUTPUT_HANDLE);
    HANDLE stderr_handle = GetStdHandle(STD_ERROR_HANDLE);
    startup_info.StartupInfo.hStdInput = stdin_handle;
    startup_info.StartupInfo.hStdOutput = stdout_handle;
    startup_info.StartupInfo.hStdError = stderr_handle;
    startup_info.StartupInfo.dwFlags = STARTF_USESTDHANDLES;
    SIZE_T size = 0;
    // The call to determine the size of an attribute list always fails with
    // ERROR_INSUFFICIENT_BUFFER and that error should be ignored.
    if (!InitializeProcThreadAttributeList(nullptr, 1, 0, &size) &&
        (GetLastError() != ERROR_INSUFFICIENT_BUFFER)) {
      return CleanupAndReturnError();
    }
    attribute_list_ = reinterpret_cast<LPPROC_THREAD_ATTRIBUTE_LIST>(
        Dart_ScopeAllocate(size));
    ZeroMemory(attribute_list_, size);
    if (!InitializeProcThreadAttributeList(attribute_list_, 1, 0, &size)) {
      return CleanupAndReturnError();
    }
    inherited_handles_ = {stdin_handle, stdout_handle, stderr_handle};
    if (!UpdateProcThreadAttribute(
            attribute_list_, 0, PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
            inherited_handles_.data(),
            inherited_handles_.size() * sizeof(HANDLE), nullptr, nullptr)) {
      return CleanupAndReturnError();
    }
    startup_info.lpAttributeList = attribute_list_;

    PROCESS_INFORMATION process_info;
    ZeroMemory(&process_info, sizeof(process_info));

    // Create process.
    DWORD creation_flags =
        EXTENDED_STARTUPINFO_PRESENT | CREATE_UNICODE_ENVIRONMENT;
    BOOL result = CreateProcessW(
        nullptr,  // ApplicationName
        command_line_,
        nullptr,  // ProcessAttributes
        nullptr,  // ThreadAttributes
        TRUE,     // InheritHandles
        creation_flags, environment_block_, system_working_directory_,
        reinterpret_cast<STARTUPINFOW*>(&startup_info), &process_info);

    if (result == 0) {
      return SetOsErrorMessage(os_error_message_);
    }
    child_process_handle_ = process_info.hProcess;
    CloseHandle(process_info.hThread);
    CloseHandle(stdin_handle);
    CloseHandle(stdout_handle);
    CloseHandle(stderr_handle);

    // Return process id.
    *id_ = process_info.dwProcessId;
    return 0;
  }

  int CreatePipes() {
    // Generate unique pipe names for the four named pipes needed.
    wchar_t pipe_names[4][kMaxPipeNameSize];
    int status = GenerateNames<4>(pipe_names);
    if (status != 0) {
      SetOsErrorMessage(os_error_message_);
      Syslog::PrintErr("UuidCreateSequential failed %d\n", status);
      return status;
    }

    if (mode_ != kDetached) {
      // Open pipes for stdin, stdout, stderr and for communicating the exit
      // code.
      if (Process::ModeHasStdio(mode_)) {
        if (!CreateProcessPipe(stdin_handles_, pipe_names[0], kInheritRead) ||
            !CreateProcessPipe(stdout_handles_, pipe_names[1], kInheritWrite) ||
            !CreateProcessPipe(stderr_handles_, pipe_names[2], kInheritWrite)) {
          return CleanupAndReturnError();
        }
      }
      // Only open exit code pipe for non detached processes.
      if (Process::ModeIsAttached(mode_)) {
        if (!CreateProcessPipe(exit_handles_, pipe_names[3], kInheritNone)) {
          return CleanupAndReturnError();
        }
      }
    } else {
      // Open NUL for stdin, stdout, and stderr.
      stdin_handles_[kReadHandle] = OpenNul();
      if (stdin_handles_[kReadHandle] == INVALID_HANDLE_VALUE) {
        return CleanupAndReturnError();
      }

      stdout_handles_[kWriteHandle] = OpenNul();
      if (stdout_handles_[kWriteHandle] == INVALID_HANDLE_VALUE) {
        return CleanupAndReturnError();
      }

      stderr_handles_[kWriteHandle] = OpenNul();
      if (stderr_handles_[kWriteHandle] == INVALID_HANDLE_VALUE) {
        return CleanupAndReturnError();
      }
    }
    return 0;
  }

  int CleanupAndReturnError() {
    int error_code = SetOsErrorMessage(os_error_message_);
    CloseProcessPipes(stdin_handles_, stdout_handles_, stderr_handles_,
                      exit_handles_);
    return error_code;
  }

  HANDLE stdin_handles_[2];
  HANDLE stdout_handles_[2];
  HANDLE stderr_handles_[2];
  HANDLE exit_handles_[2];
  HANDLE child_process_handle_;

  const wchar_t* system_working_directory_;
  wchar_t* command_line_;
  wchar_t* environment_block_;
  std::vector<HANDLE> inherited_handles_;
  LPPROC_THREAD_ATTRIBUTE_LIST attribute_list_;

  const char* path_;
  const char* working_directory_;
  ProcessStartMode mode_;
  intptr_t* in_;
  intptr_t* out_;
  intptr_t* err_;
  intptr_t* id_;
  intptr_t* exit_handler_;
  char** os_error_message_;

 private:
  DISALLOW_ALLOCATION();
  DISALLOW_IMPLICIT_CONSTRUCTORS(ProcessStarter);
};

int Process::Start(Namespace* namespc,
                   const char* path,
                   const char* arguments[],
                   intptr_t arguments_length,
                   const char* working_directory,
                   char* environment[],
                   intptr_t environment_length,
                   ProcessStartMode mode,
                   intptr_t* in,
                   intptr_t* out,
                   intptr_t* err,
                   intptr_t* id,
                   intptr_t* exit_handler,
                   char** os_error_message) {
  ProcessStarter starter(path, arguments, arguments_length, working_directory,
                         environment, environment_length, mode, in, out, err,
                         id, exit_handler, os_error_message);
  return starter.Start();
}

class BufferList : public BufferListBase {
 public:
  BufferList() : read_pending_(true) {}

  // Indicate that data has been read into the buffer provided to
  // overlapped read.
  void DataIsRead(intptr_t size) {
    ASSERT(read_pending_ == true);
    set_data_size(data_size() + size);
    set_free_size(free_size() - size);
    ASSERT(free_size() >= 0);
    read_pending_ = false;
  }

  // The access to the read buffer for overlapped read.
  bool GetReadBuffer(uint8_t** buffer, intptr_t* size) {
    ASSERT(!read_pending_);
    if (free_size() == 0) {
      if (!Allocate()) {
        return false;
      }
    }
    ASSERT(free_size() > 0);
    ASSERT(free_size() <= kBufferSize);
    *buffer = FreeSpaceAddress();
    *size = free_size();
    read_pending_ = true;
    return true;
  }

  intptr_t GetDataSize() { return data_size(); }

  uint8_t* GetFirstDataBuffer() {
    ASSERT(head() != nullptr);
    ASSERT(head() == tail());
    ASSERT(data_size() <= kBufferSize);
    return head()->data();
  }

  void FreeDataBuffer() { Free(); }

 private:
  bool read_pending_;

  DISALLOW_COPY_AND_ASSIGN(BufferList);
};

class OverlappedHandle {
 public:
  OverlappedHandle() {}

  void Init(HANDLE handle, HANDLE event) {
    handle_ = handle;
    event_ = event;
    ClearOverlapped();
  }

  bool HasEvent(HANDLE event) { return (event_ == event); }

  bool Read() {
    // Get the data read as a result of a completed overlapped operation.
    if (overlapped_.InternalHigh > 0) {
      buffer_.DataIsRead(overlapped_.InternalHigh);
    } else {
      buffer_.DataIsRead(0);
    }

    // Keep reading until error or pending operation.
    while (true) {
      ClearOverlapped();
      uint8_t* buffer;
      intptr_t buffer_size;
      if (!buffer_.GetReadBuffer(&buffer, &buffer_size)) {
        return false;
      }
      BOOL ok = ReadFile(handle_, buffer, buffer_size, nullptr, &overlapped_);
      if (!ok) {
        return (GetLastError() == ERROR_IO_PENDING);
      }
      buffer_.DataIsRead(overlapped_.InternalHigh);
    }
  }

  Dart_Handle GetData() { return buffer_.GetData(); }

  intptr_t GetDataSize() { return buffer_.GetDataSize(); }

  uint8_t* GetFirstDataBuffer() { return buffer_.GetFirstDataBuffer(); }

  void FreeDataBuffer() { return buffer_.FreeDataBuffer(); }

#if defined(DEBUG)
  bool IsEmpty() const { return buffer_.IsEmpty(); }
#endif

  void Close() {
    CloseHandle(handle_);
    CloseHandle(event_);
    handle_ = INVALID_HANDLE_VALUE;
    overlapped_.hEvent = INVALID_HANDLE_VALUE;
  }

 private:
  void ClearOverlapped() {
    memset(&overlapped_, 0, sizeof(overlapped_));
    // |FileHandle| constructor eagerly associates the given handle with
    // |EventHandler|'s completion port. However we don't want to notify
    // that completion port when |ReadFile| operation completes because
    // we are manually draining the pipe here instead of using |EventHandler|.
    // Setting LSB of |hEvent| to 1 prevents completion packets from being
    // enqueued. See documentation for |GetQueuedCompletionStatus| (specifically
    // notes for |lpOverlapped| argument).
    overlapped_.hEvent =
        reinterpret_cast<HANDLE>(reinterpret_cast<uintptr_t>(event_) | 0x1);
  }

  OVERLAPPED overlapped_;
  HANDLE handle_;
  HANDLE event_;
  BufferList buffer_;

  DISALLOW_ALLOCATION();
  DISALLOW_COPY_AND_ASSIGN(OverlappedHandle);
};

bool Process::Wait(intptr_t pid,
                   intptr_t in,
                   intptr_t out,
                   intptr_t err,
                   intptr_t exit_event,
                   ProcessResult* result) {
  // Close input to the process right away.
  reinterpret_cast<FileHandle*>(in)->Close();

  // All pipes created to the sub-process support overlapped IO.
  FileHandle* stdout_handle = reinterpret_cast<FileHandle*>(out);
  ASSERT(stdout_handle->supports_overlapped_io());
  FileHandle* stderr_handle = reinterpret_cast<FileHandle*>(err);
  ASSERT(stderr_handle->supports_overlapped_io());
  FileHandle* exit_handle = reinterpret_cast<FileHandle*>(exit_event);
  ASSERT(exit_handle->supports_overlapped_io());

  // Create three events for overlapped IO. These are created as already
  // signalled to ensure they have read called at least once.
  const int kHandles = 3;
  HANDLE events[kHandles];
  for (int i = 0; i < kHandles; i++) {
    events[i] = CreateEvent(nullptr, FALSE, TRUE, nullptr);
  }

  // Setup the structure for handling overlapped IO.
  OverlappedHandle oh[kHandles];
  oh[0].Init(stdout_handle->handle(), events[0]);
  oh[1].Init(stderr_handle->handle(), events[1]);
  oh[2].Init(exit_handle->handle(), events[2]);

  // Continue until all handles are closed.
  int alive = kHandles;
  while (alive > 0) {
    // Blocking call waiting for events from the child process.
    DWORD wait_result = WaitForMultipleObjects(alive, events, FALSE, INFINITE);

    // Find the handle signalled.
    int index = wait_result - WAIT_OBJECT_0;
    for (int i = 0; i < kHandles; i++) {
      if (oh[i].HasEvent(events[index])) {
        bool ok = oh[i].Read();
        if (!ok) {
          if (GetLastError() == ERROR_BROKEN_PIPE) {
            oh[i].Close();
            alive--;
            if (index < alive) {
              events[index] = events[alive];
            }
          } else if (err != ERROR_IO_PENDING) {
            DWORD e = GetLastError();
            oh[0].Close();
            oh[1].Close();
            oh[2].Close();
            SetLastError(e);
            return false;
          }
        }
        break;
      }
    }
  }

  // All handles closed and all data read.
  result->set_stdout_data(oh[0].GetData());
  result->set_stderr_data(oh[1].GetData());
  DEBUG_ASSERT(oh[0].IsEmpty());
  DEBUG_ASSERT(oh[1].IsEmpty());

  // Calculate the exit code.
  ASSERT(oh[2].GetDataSize() == 8);
  uint32_t exit_codes[2];
  memmove(&exit_codes, oh[2].GetFirstDataBuffer(), sizeof(exit_codes));
  oh[2].FreeDataBuffer();
  intptr_t exit_code = exit_codes[0];
  intptr_t negative = exit_codes[1];
  if (negative != 0) {
    exit_code = -exit_code;
  }
  result->set_exit_code(exit_code);

  return true;
}

int Process::Exec(Namespace* namespc,
                  const char* path,
                  const char* arguments[],
                  intptr_t arguments_length,
                  const char* working_directory,
                  char* errmsg,
                  intptr_t errmsg_len) {
  // Create a Job object with JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE
  HANDLE hjob = CreateJobObject(nullptr, nullptr);
  if (hjob == nullptr) {
    BufferFormatter f(errmsg, errmsg_len);
    f.Printf("Process::Exec - CreateJobObject failed %d\n", GetLastError());
    return -1;
  }
  JOBOBJECT_EXTENDED_LIMIT_INFORMATION info;
  DWORD qresult;
  if (!QueryInformationJobObject(hjob, JobObjectExtendedLimitInformation, &info,
                                 sizeof(JOBOBJECT_EXTENDED_LIMIT_INFORMATION),
                                 &qresult)) {
    BufferFormatter f(errmsg, errmsg_len);
    f.Printf("Process::Exec - QueryInformationJobObject failed %d\n",
             GetLastError());
    return -1;
  }
  info.BasicLimitInformation.LimitFlags |= JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
  if (!SetInformationJobObject(hjob, JobObjectExtendedLimitInformation, &info,
                               sizeof(JOBOBJECT_EXTENDED_LIMIT_INFORMATION))) {
    BufferFormatter f(errmsg, errmsg_len);
    f.Printf("Process::Exec - SetInformationJobObject failed %d\n",
             GetLastError());
    return -1;
  }

  // Put the current process into the job object (there is a race here
  // as the process can crash before it is in the Job object, but since
  // we haven't spawned any children yet this race is harmless)
  if (!AssignProcessToJobObject(hjob, GetCurrentProcess())) {
    BufferFormatter f(errmsg, errmsg_len);
    f.Printf("Process::Exec - AssignProcessToJobObject failed %d\n",
             GetLastError());
    return -1;
  }

  // Spawn the new child process (this child will automatically get
  // added to the Job object).
  // If the parent process is killed or it crashes the Job object
  // will get destroyed and all the child processes will also get killed.
  // arguments includes the name of the executable to run which is the same
  // as the value passed in 'path', we strip that off when starting the
  // process.
  intptr_t pid = -1;
  char* os_error_message = nullptr;  // Scope allocated by Process::Start.
  ProcessStarter starter(path, &(arguments[1]), (arguments_length - 1),
                         working_directory, nullptr, 0, kInheritStdio, nullptr,
                         nullptr, nullptr, &pid, nullptr, &os_error_message);
  int result = starter.StartForExec();
  if (result != 0) {
    BufferFormatter f(errmsg, errmsg_len);
    f.Printf("Process::Exec - %s\n", os_error_message);
    return -1;
  }

  // Now wait for this child process to terminate (normal exit or crash).
  HANDLE child_process = starter.child_process_handle_;
  ASSERT(child_process != INVALID_HANDLE_VALUE);
  DWORD wait_result = WaitForSingleObject(child_process, INFINITE);
  if (wait_result != WAIT_OBJECT_0) {
    BufferFormatter f(errmsg, errmsg_len);
    f.Printf("Process::Exec - WaitForSingleObject failed %d\n", GetLastError());
    CloseHandle(child_process);
    return -1;
  }
  int retval;
  if (!GetExitCodeProcess(child_process, reinterpret_cast<DWORD*>(&retval))) {
    BufferFormatter f(errmsg, errmsg_len);
    f.Printf("Process::Exec - GetExitCodeProcess failed %d\n", GetLastError());
    CloseHandle(child_process);
    return -1;
  }
  CloseHandle(child_process);
  // We exit the process here to simulate the same behaviour as exec on systems
  // that support it.
  ExitProcess(retval);
  return 0;
}

bool Process::Kill(intptr_t id, int signal) {
  USE(signal);  // signal is not used on Windows.
  HANDLE process_handle;
  HANDLE wait_handle;
  HANDLE exit_pipe;
  // First check the process info list for the process to get a handle to it.
  bool success = ProcessInfoList::LookupProcess(id, &process_handle,
                                                &wait_handle, &exit_pipe);
  // For detached processes we don't have the process registered in the
  // process info list. Try to look it up through the OS.
  if (!success) {
    process_handle = OpenProcess(PROCESS_TERMINATE, FALSE, id);
    // The process is already dead.
    if (process_handle == INVALID_HANDLE_VALUE) {
      return false;
    }
  }
  BOOL result = TerminateProcess(process_handle, -1);
  return result ? true : false;
}

void Process::TerminateExitCodeHandler() {
  // Nothing needs to be done on Windows.
}

intptr_t Process::CurrentProcessId() {
  return static_cast<intptr_t>(GetCurrentProcessId());
}

int64_t Process::CurrentRSS() {
// Although the documentation at
// https://docs.microsoft.com/en-us/windows/win32/api/psapi/nf-psapi-getprocessmemoryinfo
// claims that GetProcessMemoryInfo is UWP compatible, it is actually not
// hence this function cannot work when compiled in UWP mode.
#ifdef DART_TARGET_OS_WINDOWS_UWP
  return -1;
#else
  PROCESS_MEMORY_COUNTERS pmc;
  if (!GetProcessMemoryInfo(GetCurrentProcess(), &pmc, sizeof(pmc))) {
    return -1;
  }
  return pmc.WorkingSetSize;
#endif
}

int64_t Process::MaxRSS() {
#ifdef DART_TARGET_OS_WINDOWS_UWP
  return -1;
#else
  PROCESS_MEMORY_COUNTERS pmc;
  if (!GetProcessMemoryInfo(GetCurrentProcess(), &pmc, sizeof(pmc))) {
    return -1;
  }
  return pmc.PeakWorkingSetSize;
#endif
}

static SignalInfo* signal_handlers = nullptr;
static Mutex* signal_mutex = nullptr;

SignalInfo::~SignalInfo() {
  FileHandle* file_handle = reinterpret_cast<FileHandle*>(fd_);
  file_handle->Close();
  file_handle->Release();
}

BOOL WINAPI SignalHandler(DWORD signal) {
  MutexLocker lock(signal_mutex);
  const SignalInfo* handler = signal_handlers;
  bool handled = false;
  while (handler != nullptr) {
    if (handler->signal() == signal) {
      int value = 0;
      SocketBase::Write(handler->fd(), &value, 1, SocketBase::kAsync);
      handled = true;
    }
    handler = handler->next();
  }
  return handled;
}

intptr_t GetWinSignal(intptr_t signal) {
  switch (signal) {
    case kSighup:
      return CTRL_CLOSE_EVENT;
    case kSigint:
      return CTRL_C_EVENT;
    default:
      return -1;
  }
}

intptr_t Process::SetSignalHandler(intptr_t signal) {
  signal = GetWinSignal(signal);
  if (signal == -1) {
    SetLastError(ERROR_NOT_SUPPORTED);
    return -1;
  }

  // Generate a unique pipe name for the named pipe.
  wchar_t pipe_name[kMaxPipeNameSize];
  int status = GenerateNames<1>(&pipe_name);
  if (status != 0) {
    return status;
  }

  HANDLE fds[2];
  if (!CreateProcessPipe(fds, pipe_name, kInheritNone)) {
    int error_code = GetLastError();
    CloseProcessPipe(fds);
    SetLastError(error_code);
    return -1;
  }
  MutexLocker lock(signal_mutex);
  FileHandle* write_handle = new FileHandle(fds[kWriteHandle]);
  intptr_t write_fd = reinterpret_cast<intptr_t>(write_handle);
  if (signal_handlers == nullptr) {
    if (SetConsoleCtrlHandler(SignalHandler, true) == 0) {
      int error_code = GetLastError();
      // Since SetConsoleCtrlHandler failed, there will be no subsequent IO
      // operation on this handle. Release() it.
      write_handle->Release();
      CloseProcessPipe(fds);
      SetLastError(error_code);
      return -1;
    }
  }
  signal_handlers =
      new SignalInfo(write_fd, signal, /*oldact=*/nullptr, signal_handlers);
  return reinterpret_cast<intptr_t>(new FileHandle(fds[kReadHandle]));
}

void Process::ClearSignalHandler(intptr_t signal, Dart_Port port) {
  signal = GetWinSignal(signal);
  if (signal == -1) {
    return;
  }
  MutexLocker lock(signal_mutex);
  SignalInfo* handler = signal_handlers;
  while (handler != nullptr) {
    bool remove = false;
    if (handler->signal() == signal) {
      if ((port == ILLEGAL_PORT) || (handler->port() == port)) {
        if (signal_handlers == handler) {
          signal_handlers = handler->next();
        }
        handler->Unlink();
        remove = true;
      }
    }
    SignalInfo* next = handler->next();
    if (remove) {
      delete handler;
    }
    handler = next;
  }
  if (signal_handlers == nullptr) {
    USE(SetConsoleCtrlHandler(SignalHandler, false));
  }
}

void Process::ClearSignalHandlerByFd(intptr_t fd, Dart_Port port) {
  MutexLocker lock(signal_mutex);
  SignalInfo* handler = signal_handlers;
  while (handler != nullptr) {
    bool remove = false;
    if (handler->fd() == fd) {
      if ((port == ILLEGAL_PORT) || (handler->port() == port)) {
        if (signal_handlers == handler) {
          signal_handlers = handler->next();
        }
        handler->Unlink();
        FileHandle* file_handle = reinterpret_cast<FileHandle*>(handler->fd());
        file_handle->Release();
        remove = true;
      }
    }
    SignalInfo* next = handler->next();
    if (remove) {
      delete handler;
    }
    handler = next;
  }
  if (signal_handlers == nullptr) {
    USE(SetConsoleCtrlHandler(SignalHandler, false));
  }
}

void ProcessInfoList::Init() {
  active_processes_ = nullptr;
  ASSERT(ProcessInfoList::mutex_ == nullptr);
  ProcessInfoList::mutex_ = new Mutex();
}

void ProcessInfoList::Cleanup() {
  ASSERT(ProcessInfoList::mutex_ != nullptr);
  delete ProcessInfoList::mutex_;
  ProcessInfoList::mutex_ = nullptr;
}

void Process::Init() {
  ProcessInfoList::Init();

  signal_handlers = nullptr;
  ASSERT(signal_mutex == nullptr);
  signal_mutex = new Mutex();

  ASSERT(Process::global_exit_code_mutex_ == nullptr);
  Process::global_exit_code_mutex_ = new Mutex();
}

void Process::Cleanup() {
  ClearAllSignalHandlers();

  ASSERT(signal_mutex != nullptr);
  delete signal_mutex;
  signal_mutex = nullptr;

  ASSERT(Process::global_exit_code_mutex_ != nullptr);
  delete Process::global_exit_code_mutex_;
  Process::global_exit_code_mutex_ = nullptr;

  ProcessInfoList::Cleanup();
}

}  // namespace bin
}  // namespace dart

#endif  // defined(DART_HOST_OS_WINDOWS)