Example #1
0
static bool parse_relative_root(w_root_t *root, w_query *res, json_t *query)
{
  json_t *relative_root;
  w_string_t *path, *canon_path;

  relative_root = json_object_get(query, "relative_root");
  if (!relative_root) {
    return true;
  }

  if (!json_is_string(relative_root)) {
    res->errmsg = strdup("'relative_root' must be a string");
    return false;
  }

  path = w_string_new(json_string_value(relative_root));
  canon_path = w_string_canon_path(path);
  res->relative_root = w_string_path_cat(root->root_path, canon_path);
  res->relative_root_slash = w_string_make_printf("%.*s%c",
        res->relative_root->len, res->relative_root->buf,
        WATCHMAN_DIR_SEP);
  w_string_delref(path);
  w_string_delref(canon_path);

  return true;
}
Example #2
0
w_string_t *w_query_ctx_get_wholename(
    struct w_query_ctx *ctx
)
{
  w_string_t *full_name;
  uint32_t name_start;

  if (ctx->wholename) {
    return ctx->wholename;
  }

  if (ctx->query->relative_root != NULL) {
    // At this point every path should start with the relative root, so this is
    // legal
    name_start = ctx->query->relative_root->len + 1;
  } else {
    name_start = ctx->root->root_path->len + 1;
  }

  full_name = w_string_path_cat(compute_parent_path(ctx, ctx->file),
                                w_file_get_name(ctx->file));

  // Record the name relative to the root
  ctx->wholename = w_string_slice(full_name, name_start,
      full_name->len - name_start);
  w_string_delref(full_name);

  return ctx->wholename;
}
Example #3
0
static bool portfs_root_consume_notify(watchman_global_watcher_t watcher,
    w_root_t *root, struct watchman_pending_collection *coll)
{
  struct portfs_root_state *state = root->watch;
  uint_t i, n;
  struct timeval now;
  unused_parameter(watcher);

  errno = 0;

  n = 1;
  if (port_getn(state->port_fd, state->portevents,
        sizeof(state->portevents) / sizeof(state->portevents[0]), &n, NULL)) {
    if (errno == EINTR) {
      return false;
    }
    w_log(W_LOG_FATAL, "port_getn: %s\n",
        strerror(errno));
  }

  w_log(W_LOG_DBG, "port_getn: n=%u\n", n);

  if (n == 0) {
    return false;
  }

  for (i = 0; i < n; i++) {
    if (IS_DIR_BIT_SET(state->portevents[i].portev_user)) {
      struct watchman_dir *dir = DECODE_DIR(state->portevents[i].portev_user);
      uint32_t pe = state->portevents[i].portev_events;

      w_log(W_LOG_DBG, "port: dir %.*s [0x%x]\n",
          dir->path->len, dir->path->buf, pe);

      if ((pe & (FILE_RENAME_FROM|UNMOUNTED|MOUNTEDOVER|FILE_DELETE))
          && w_string_equal(dir->path, root->root_path)) {

        w_log(W_LOG_ERR,
          "root dir %s has been (re)moved (code 0x%x), canceling watch\n",
          root->root_path->buf, pe);

        w_root_cancel(root);
        return false;
      }
      w_pending_coll_add(coll, dir->path, false, now, true);

    } else {
      struct watchman_file *file = state->portevents[i].portev_user;
      w_string_t *path;

      path = w_string_path_cat(file->parent->path, file->name);
      w_pending_coll_add(coll, path, true, now, true);
      w_log(W_LOG_DBG, "port: file %.*s\n", path->len, path->buf);
      w_string_delref(path);
    }
  }

  return true;
}
Example #4
0
static bool kqueue_root_consume_notify(watchman_global_watcher_t watcher,
    w_root_t *root, struct watchman_pending_collection *coll)
{
  struct kqueue_root_state *state = root->watch;
  int n;
  int i;
  struct timespec ts = { 0, 0 };
  struct timeval now;
  unused_parameter(watcher);

  errno = 0;

  w_log(W_LOG_DBG, "kqueue(%s)\n", root->root_path->buf);
  n = kevent(state->kq_fd, NULL, 0,
      state->keventbuf, sizeof(state->keventbuf) / sizeof(state->keventbuf[0]),
      &ts);
  w_log(W_LOG_DBG, "consume_kqueue: %s n=%d err=%s\n",
      root->root_path->buf, n, strerror(errno));
  if (root->cancelled) {
    return 0;
  }

  gettimeofday(&now, NULL);
  for (i = 0; n > 0 && i < n; i++) {
    uint32_t fflags = state->keventbuf[i].fflags;

    if (IS_DIR_BIT_SET(state->keventbuf[i].udata)) {
      struct watchman_dir *dir = DECODE_DIR(state->keventbuf[i].udata);

      w_log(W_LOG_DBG, " KQ dir %s [0x%x]\n", dir->path->buf, fflags);
      if ((fflags & (NOTE_DELETE|NOTE_RENAME|NOTE_REVOKE)) &&
          w_string_equal(dir->path, root->root_path)) {
        w_log(W_LOG_ERR,
            "root dir %s has been (re)moved [code 0x%x], canceling watch\n",
            root->root_path->buf, fflags);
        w_root_cancel(root);
        return 0;
      }
      w_pending_coll_add(coll, dir->path, false, now, false);
    } else {
      // NetBSD defines udata as intptr type, so the cast is necessary
      struct watchman_file *file = (void *)state->keventbuf[i].udata;

      w_string_t *path;

      path = w_string_path_cat(file->parent->path, file->name);
      w_pending_coll_add(coll, path, true, now, true);
      w_log(W_LOG_DBG, " KQ file %.*s [0x%x]\n", path->len, path->buf, fflags);
      w_string_delref(path);
    }
  }

  return n > 0;
}
Example #5
0
static bool kqueue_root_start_watch_file(watchman_global_watcher_t watcher,
      w_root_t *root, struct watchman_file *file) {
  struct kqueue_root_state *state = root->watch;
  struct kevent k;
  w_ht_val_t fdval;
  int fd;
  w_string_t *full_name;
  unused_parameter(watcher);

  full_name = w_string_path_cat(file->parent->path, file->name);
  pthread_mutex_lock(&state->lock);
  if (w_ht_lookup(state->name_to_fd, w_ht_ptr_val(full_name), &fdval, false)) {
    // Already watching it
    pthread_mutex_unlock(&state->lock);
    return true;
  }
  pthread_mutex_unlock(&state->lock);

  w_log(W_LOG_DBG, "watch_file(%s)\n", full_name->buf);

  fd = open(full_name->buf, O_EVTONLY|O_CLOEXEC);
  if (fd == -1) {
    w_log(W_LOG_ERR, "failed to open %s O_EVTONLY: %s\n",
        full_name->buf, strerror(errno));
    w_string_delref(full_name);
    return false;
  }

  memset(&k, 0, sizeof(k));
  EV_SET(&k, fd, EVFILT_VNODE, EV_ADD|EV_CLEAR,
      NOTE_WRITE|NOTE_DELETE|NOTE_EXTEND|NOTE_RENAME|NOTE_ATTRIB,
      0, full_name);

  pthread_mutex_lock(&state->lock);
  w_ht_replace(state->name_to_fd, w_ht_ptr_val(full_name), fd);
  w_ht_replace(state->fd_to_name, fd, w_ht_ptr_val(full_name));
  pthread_mutex_unlock(&state->lock);

  if (kevent(state->kq_fd, &k, 1, NULL, 0, 0)) {
    w_log(W_LOG_DBG, "kevent EV_ADD file %s failed: %s",
        full_name->buf, strerror(errno));
    close(fd);
    pthread_mutex_lock(&state->lock);
    w_ht_del(state->name_to_fd, w_ht_ptr_val(full_name));
    w_ht_del(state->fd_to_name, fd);
    pthread_mutex_unlock(&state->lock);
  } else {
    w_log(W_LOG_DBG, "kevent file %s -> %d\n", full_name->buf, fd);
  }
  w_string_delref(full_name);

  return true;
}
Example #6
0
w_string_t *w_query_ctx_get_wholename(
    struct w_query_ctx *ctx
)
{
  w_string_t *full_name;
  uint32_t name_start;

  if (ctx->wholename) {
    return ctx->wholename;
  }

  name_start = ctx->root->root_path->len + 1;

  full_name = w_string_path_cat(ctx->file->parent->path, ctx->file->name);
  // Record the name relative to the root
  ctx->wholename = w_string_slice(full_name, name_start,
      full_name->len - name_start);
  w_string_delref(full_name);

  return ctx->wholename;
}
Example #7
0
static void *readchanges_thread(void *arg) {
  w_root_t *root = arg;
  struct winwatch_root_state *state = root->watch;
  DWORD size = WATCHMAN_BATCH_LIMIT * (sizeof(FILE_NOTIFY_INFORMATION) + 512);
  char *buf;
  DWORD err, filter;
  OVERLAPPED olap;
  BOOL initiate_read = true;
  HANDLE handles[2] = { state->olap, state->ping };
  DWORD bytes;

  w_set_thread_name("readchange %.*s",
      root->root_path->len, root->root_path->buf);

  // Block until winmatch_root_st is waiting for our initialization
  pthread_mutex_lock(&state->mtx);

  filter = FILE_NOTIFY_CHANGE_FILE_NAME|FILE_NOTIFY_CHANGE_DIR_NAME|
    FILE_NOTIFY_CHANGE_ATTRIBUTES|FILE_NOTIFY_CHANGE_SIZE|
    FILE_NOTIFY_CHANGE_LAST_WRITE;

  memset(&olap, 0, sizeof(olap));
  olap.hEvent = state->olap;

  buf = malloc(size);
  if (!buf) {
    w_log(W_LOG_ERR, "failed to allocate %u bytes for dirchanges buf\n", size);
    goto out;
  }

  if (!ReadDirectoryChangesW(state->dir_handle, buf, size,
        TRUE, filter, NULL, &olap, NULL)) {
    err = GetLastError();
    w_log(W_LOG_ERR,
        "ReadDirectoryChangesW: failed, cancel watch. %s\n",
        win32_strerror(err));
    w_root_lock(root);
    w_root_cancel(root);
    w_root_unlock(root);
    goto out;
  }
  // Signal that we are done with init.  We MUST do this AFTER our first
  // successful ReadDirectoryChangesW, otherwise there is a race condition
  // where we'll miss observing the cookie for a query that comes in
  // after we've crawled but before the watch is established.
  w_log(W_LOG_DBG, "ReadDirectoryChangesW signalling as init done");
  pthread_cond_signal(&state->cond);
  pthread_mutex_unlock(&state->mtx);
  initiate_read = false;

  // The state->mutex must not be held when we enter the loop
  while (!root->cancelled) {
    if (initiate_read) {
      if (!ReadDirectoryChangesW(state->dir_handle,
            buf, size, TRUE, filter, NULL, &olap, NULL)) {
        err = GetLastError();
        w_log(W_LOG_ERR,
            "ReadDirectoryChangesW: failed, cancel watch. %s\n",
            win32_strerror(err));
        w_root_lock(root);
        w_root_cancel(root);
        w_root_unlock(root);
        break;
      } else {
        initiate_read = false;
      }
    }

    w_log(W_LOG_DBG, "waiting for change notifications");
    DWORD status = WaitForMultipleObjects(2, handles, FALSE, INFINITE);

    if (status == WAIT_OBJECT_0) {
      bytes = 0;
      if (!GetOverlappedResult(state->dir_handle, &olap,
            &bytes, FALSE)) {
        err = GetLastError();
        w_log(W_LOG_ERR, "overlapped ReadDirectoryChangesW(%s): 0x%x %s\n",
            root->root_path->buf,
            err, win32_strerror(err));

        if (err == ERROR_INVALID_PARAMETER && size > NETWORK_BUF_SIZE) {
          // May be a network buffer related size issue; the docs say that
          // we can hit this when watching a UNC path. Let's downsize and
          // retry the read just one time
          w_log(W_LOG_ERR, "retrying watch for possible network location %s "
              "with smaller buffer\n", root->root_path->buf);
          size = NETWORK_BUF_SIZE;
          initiate_read = true;
          continue;
        }

        if (err == ERROR_NOTIFY_ENUM_DIR) {
          w_root_schedule_recrawl(root, "ERROR_NOTIFY_ENUM_DIR");
        } else {
          w_log(W_LOG_ERR, "Cancelling watch for %s\n",
              root->root_path->buf);
          w_root_lock(root);
          w_root_cancel(root);
          w_root_unlock(root);
          break;
        }
      } else {
        PFILE_NOTIFY_INFORMATION not = (PFILE_NOTIFY_INFORMATION)buf;
        struct winwatch_changed_item *head = NULL, *tail = NULL;
        while (true) {
          struct winwatch_changed_item *item;
          DWORD n_chars;
          w_string_t *name, *full;

          // FileNameLength is in BYTES, but FileName is WCHAR
          n_chars = not->FileNameLength / sizeof(not->FileName[0]);
          name = w_string_new_wchar(not->FileName, n_chars);

          full = w_string_path_cat(root->root_path, name);
          w_string_delref(name);

          if (w_is_ignored(root, full->buf, full->len)) {
            w_string_delref(full);
          } else {
            item = calloc(1, sizeof(*item));
            item->name = full;

            if (tail) {
              tail->next = item;
            } else {
              head = item;
            }
            tail = item;
          }

          // Advance to next item
          if (not->NextEntryOffset == 0) {
            break;
          }
          not = (PFILE_NOTIFY_INFORMATION)(not->NextEntryOffset + (char*)not);
        }

        if (tail) {
          pthread_mutex_lock(&state->mtx);
          if (state->tail) {
            state->tail->next = head;
          } else {
            state->head = head;
          }
          state->tail = tail;
          pthread_mutex_unlock(&state->mtx);
          pthread_cond_signal(&state->cond);
        }
        ResetEvent(state->olap);
        initiate_read = true;
      }
    } else if (status == WAIT_OBJECT_0 + 1) {
      w_log(W_LOG_ERR, "signalled\n");
      break;
    } else {
      w_log(W_LOG_ERR, "impossible wait status=%d\n",
          status);
      break;
    }
  }

  pthread_mutex_lock(&state->mtx);
out:
  // Signal to winwatch_root_start that we're done initializing in
  // the failure path.  We'll also do this after we've completed
  // the run loop in the success path; it's a spurious wakeup but
  // harmless and saves us from adding and setting a control flag
  // in each of the failure `goto` statements. winwatch_root_dtor
  // will `pthread_join` us before `state` is freed.
  pthread_cond_signal(&state->cond);
  pthread_mutex_unlock(&state->mtx);

  if (buf) {
    free(buf);
  }
  w_log(W_LOG_DBG, "done\n");
  w_root_delref(root);
  return NULL;
}
Example #8
0
static void spawn_command(w_root_t *root,
  struct watchman_trigger_command *cmd,
  w_query_res *res,
  struct w_clockspec *since_spec)
{
  char **envp = NULL;
  uint32_t i = 0;
  int ret;
  w_stm_t stdin_file = NULL;
  json_t *args;
  char **argv = NULL;
  uint32_t env_size;
  posix_spawn_file_actions_t actions;
  posix_spawnattr_t attr;
#ifndef _WIN32
  sigset_t mask;
#endif
  long arg_max;
  size_t argspace_remaining;
  bool file_overflow = false;
  int result_log_level;
  char clockbuf[128];
  w_string_t *working_dir = NULL;

#ifdef _WIN32
  arg_max = 32*1024;
#else
  arg_max = sysconf(_SC_ARG_MAX);
#endif

  if (arg_max <= 0) {
    argspace_remaining = UINT_MAX;
  } else {
    argspace_remaining = (uint32_t)arg_max;
  }

  // Allow some misc working overhead
  argspace_remaining -= 32;

  stdin_file = prepare_stdin(cmd, res);
  if (!stdin_file) {
    w_log(W_LOG_ERR, "trigger %.*s:%s %s\n",
        (int)root->root_path->len,
        root->root_path->buf,
        cmd->triggername->buf, strerror(errno));
    return;
  }

  // Assumption: that only one thread will be executing on a given
  // cmd instance so that mutation of cmd->envht is safe.
  // This is guaranteed in the current architecture.

  if (cmd->max_files_stdin > 0 && res->num_results > cmd->max_files_stdin) {
    file_overflow = true;
  }

  // It is way too much of a hassle to try to recreate the clock value if it's
  // not a relative clock spec, and it's only going to happen on the first run
  // anyway, so just skip doing that entirely.
  if (since_spec && since_spec->tag == w_cs_clock &&
      clock_id_string(since_spec->clock.root_number, since_spec->clock.ticks,
                      clockbuf, sizeof(clockbuf))) {
    w_envp_set_cstring(cmd->envht, "WATCHMAN_SINCE", clockbuf);
  } else {
    w_envp_unset(cmd->envht, "WATCHMAN_SINCE");
  }

  if (clock_id_string(res->root_number, res->ticks,
        clockbuf, sizeof(clockbuf))) {
    w_envp_set_cstring(cmd->envht, "WATCHMAN_CLOCK", clockbuf);
  } else {
    w_envp_unset(cmd->envht, "WATCHMAN_CLOCK");
  }

  if (cmd->query->relative_root) {
    w_envp_set(cmd->envht, "WATCHMAN_RELATIVE_ROOT", cmd->query->relative_root);
  } else {
    w_envp_unset(cmd->envht, "WATCHMAN_RELATIVE_ROOT");
  }

  // Compute args
  args = json_deep_copy(cmd->command);

  if (cmd->append_files) {
    // Measure how much space the base args take up
    for (i = 0; i < json_array_size(args); i++) {
      const char *ele = json_string_value(json_array_get(args, i));

      argspace_remaining -= strlen(ele) + 1 + sizeof(char*);
    }

    // Dry run with env to compute space
    envp = w_envp_make_from_ht(cmd->envht, &env_size);
    free(envp);
    envp = NULL;
    argspace_remaining -= env_size;

    for (i = 0; i < res->num_results; i++) {
      // also: NUL terminator and entry in argv
      uint32_t size = res->results[i].relname->len + 1 + sizeof(char*);

      if (argspace_remaining < size) {
        file_overflow = true;
        break;
      }
      argspace_remaining -= size;

      json_array_append_new(
        args,
        json_string_nocheck(res->results[i].relname->buf)
      );
    }
  }

  argv = w_argv_copy_from_json(args, 0);
  json_decref(args);
  args = NULL;

  w_envp_set_bool(cmd->envht, "WATCHMAN_FILES_OVERFLOW", file_overflow);

  envp = w_envp_make_from_ht(cmd->envht, &env_size);

  posix_spawnattr_init(&attr);
#ifndef _WIN32
  sigemptyset(&mask);
  posix_spawnattr_setsigmask(&attr, &mask);
#endif
  posix_spawnattr_setflags(&attr,
      POSIX_SPAWN_SETSIGMASK|
#ifdef POSIX_SPAWN_CLOEXEC_DEFAULT
      // Darwin: close everything except what we put in file actions
      POSIX_SPAWN_CLOEXEC_DEFAULT|
#endif
      POSIX_SPAWN_SETPGROUP);

  posix_spawn_file_actions_init(&actions);

#ifndef _WIN32
  posix_spawn_file_actions_adddup2(&actions, w_stm_fileno(stdin_file),
      STDIN_FILENO);
#else
  posix_spawn_file_actions_adddup2_handle_np(&actions,
      w_stm_handle(stdin_file), STDIN_FILENO);
#endif
  if (cmd->stdout_name) {
    posix_spawn_file_actions_addopen(&actions, STDOUT_FILENO,
        cmd->stdout_name, cmd->stdout_flags, 0666);
  } else {
    posix_spawn_file_actions_adddup2(&actions, STDOUT_FILENO, STDOUT_FILENO);
  }

  if (cmd->stderr_name) {
    posix_spawn_file_actions_addopen(&actions, STDERR_FILENO,
        cmd->stderr_name, cmd->stderr_flags, 0666);
  } else {
    posix_spawn_file_actions_adddup2(&actions, STDERR_FILENO, STDERR_FILENO);
  }

  // Figure out the appropriate cwd
  {
    const char *cwd = NULL;
    working_dir = NULL;

    if (cmd->query->relative_root) {
      working_dir = cmd->query->relative_root;
    } else {
      working_dir = root->root_path;
    }
    w_string_addref(working_dir);

    json_unpack(cmd->definition, "{s:s}", "chdir", &cwd);
    if (cwd) {
      w_string_t *cwd_str = w_string_new(cwd);

      if (w_is_path_absolute(cwd)) {
        w_string_delref(working_dir);
        working_dir = cwd_str;
      } else {
        w_string_t *joined;

        joined = w_string_path_cat(working_dir, cwd_str);
        w_string_delref(cwd_str);
        w_string_delref(working_dir);

        working_dir = joined;
      }
    }

    w_log(W_LOG_DBG, "using %.*s for working dir\n", working_dir->len, working_dir->buf);
  }

  pthread_mutex_lock(&spawn_lock);
#ifndef _WIN32
  ignore_result(chdir(working_dir->buf));
#else
  posix_spawnattr_setcwd_np(&attr, working_dir->buf);
#endif
  w_string_delref(working_dir);
  working_dir = NULL;

  ret = posix_spawnp(&cmd->current_proc, argv[0], &actions, &attr, argv, envp);
  if (ret == 0) {
    w_root_addref(root);
    insert_running_pid(cmd->current_proc, root);
  } else {
    // On Darwin (at least), posix_spawn can fail but will still populate the
    // pid.  Since we use the pid to gate future spawns, we need to ensure
    // that we clear out the pid on failure, otherwise the trigger would be
    // effectively disabled for the rest of the watch lifetime
    cmd->current_proc = 0;
  }
#ifndef _WIN32
  ignore_result(chdir("/"));
#endif
  pthread_mutex_unlock(&spawn_lock);

  // If failed, we want to make sure we log enough info to figure out why
  result_log_level = res == 0 ? W_LOG_DBG : W_LOG_ERR;

  w_log(result_log_level, "posix_spawnp:\n");
  for (i = 0; argv[i]; i++) {
    w_log(result_log_level, "argv[%d] %s\n", i, argv[i]);
  }
  for (i = 0; envp[i]; i++) {
    w_log(result_log_level, "envp[%d] %s\n", i, envp[i]);
  }

  w_log(result_log_level, "trigger %.*s:%s pid=%d ret=%d %s\n",
      (int)root->root_path->len,
      root->root_path->buf,
      cmd->triggername->buf, (int)cmd->current_proc, ret, strerror(ret));

  free(argv);
  free(envp);

  posix_spawnattr_destroy(&attr);
  posix_spawn_file_actions_destroy(&actions);

  if (stdin_file) {
    w_stm_close(stdin_file);
  }
}
Example #9
0
static bool path_generator(
    w_query *query,
    w_root_t *root,
    struct w_query_ctx *ctx)
{
  struct watchman_file *f;
  uint32_t i;

  for (i = 0; i < query->npaths; i++) {
    struct watchman_dir *dir;
    w_string_t *dir_name, *file_name, *full_name;

    // Compose path with root
    full_name = w_string_path_cat(root->root_path, query->paths[i].name);

    // special case of root dir itself
    if (w_string_equal(root->root_path, full_name)) {
      // dirname on the root is outside the root, which is useless
      dir = w_root_resolve_dir(root, full_name, false);
      goto is_dir;
    }

    // Ideally, we'd just resolve it directly as a dir and be done.
    // It's not quite so simple though, because we may resolve a dir
    // that had been deleted and replaced by a file.
    // We prefer to resolve the parent and walk down.
    dir_name = w_string_dirname(full_name);
    if (!dir_name) {
      w_string_delref(full_name);
      continue;
    }

    dir = w_root_resolve_dir(root, dir_name, false);
    w_string_delref(dir_name);

    if (!dir) {
      // Doesn't exist, and never has
      w_string_delref(full_name);
      continue;
    }

    if (dir->files) {
      file_name = w_string_basename(query->paths[i].name);
      f = w_ht_val_ptr(w_ht_get(dir->files, w_ht_ptr_val(file_name)));
      w_string_delref(file_name);

      // If it's a file (but not an existent dir)
      if (f && (!f->exists || !S_ISDIR(f->st.st_mode))) {
        w_string_delref(full_name);
        if (!w_query_process_file(query, ctx, f)) {
          return false;
        }
        continue;
      }
    }

    // Is it a dir?
    dir = w_ht_val_ptr(w_ht_get(dir->dirs, w_ht_ptr_val(full_name)));
    w_string_delref(full_name);
is_dir:
    // We got a dir; process recursively to specified depth
    if (dir && !dir_generator(query, root, ctx, dir,
          query->paths[i].depth)) {
      return false;
    }
  }
  return true;
}
Example #10
0
static void spawn_command(
    const std::shared_ptr<w_root_t>& root,
    struct watchman_trigger_command* cmd,
    w_query_res* res,
    struct w_clockspec* since_spec) {
  char **envp = NULL;
  uint32_t i = 0;
  int ret;
  char **argv = NULL;
  uint32_t env_size;
  posix_spawn_file_actions_t actions;
  posix_spawnattr_t attr;
#ifndef _WIN32
  sigset_t mask;
#endif
  long arg_max;
  size_t argspace_remaining;
  bool file_overflow = false;
  int result_log_level;
  w_string_t *working_dir = NULL;

#ifdef _WIN32
  arg_max = 32*1024;
#else
  arg_max = sysconf(_SC_ARG_MAX);
#endif

  if (arg_max <= 0) {
    argspace_remaining = UINT_MAX;
  } else {
    argspace_remaining = (uint32_t)arg_max;
  }

  // Allow some misc working overhead
  argspace_remaining -= 32;

  // Record an overflow before we call prepare_stdin(), which mutates
  // and resizes the results to fit the specified limit.
  if (cmd->max_files_stdin > 0 &&
      res->resultsArray.array().size() > cmd->max_files_stdin) {
    file_overflow = true;
  }

  auto stdin_file = prepare_stdin(cmd, res);
  if (!stdin_file) {
    w_log(
        W_LOG_ERR,
        "trigger %s:%s %s\n",
        root->root_path.c_str(),
        cmd->triggername.c_str(),
        strerror(errno));
    return;
  }

  // Assumption: that only one thread will be executing on a given
  // cmd instance so that mutation of cmd->envht is safe.
  // This is guaranteed in the current architecture.

  // It is way too much of a hassle to try to recreate the clock value if it's
  // not a relative clock spec, and it's only going to happen on the first run
  // anyway, so just skip doing that entirely.
  if (since_spec && since_spec->tag == w_cs_clock) {
    w_envp_set_cstring(
        cmd->envht,
        "WATCHMAN_SINCE",
        since_spec->clock.position.toClockString().c_str());
  } else {
    w_envp_unset(cmd->envht, "WATCHMAN_SINCE");
  }

  w_envp_set_cstring(
      cmd->envht,
      "WATCHMAN_CLOCK",
      res->clockAtStartOfQuery.toClockString().c_str());

  if (cmd->query->relative_root) {
    w_envp_set(cmd->envht, "WATCHMAN_RELATIVE_ROOT", cmd->query->relative_root);
  } else {
    w_envp_unset(cmd->envht, "WATCHMAN_RELATIVE_ROOT");
  }

  // Compute args
  auto args = json_deep_copy(cmd->command);

  if (cmd->append_files) {
    // Measure how much space the base args take up
    for (i = 0; i < json_array_size(args); i++) {
      const char *ele = json_string_value(json_array_get(args, i));

      argspace_remaining -= strlen(ele) + 1 + sizeof(char*);
    }

    // Dry run with env to compute space
    envp = w_envp_make_from_ht(cmd->envht, &env_size);
    free(envp);
    envp = NULL;
    argspace_remaining -= env_size;

    for (const auto& item : res->dedupedFileNames) {
      // also: NUL terminator and entry in argv
      uint32_t size = item.size() + 1 + sizeof(char*);

      if (argspace_remaining < size) {
        file_overflow = true;
        break;
      }
      argspace_remaining -= size;

      json_array_append_new(args, w_string_to_json(item));
    }
  }

  argv = w_argv_copy_from_json(args, 0);
  args = nullptr;

  w_envp_set_bool(cmd->envht, "WATCHMAN_FILES_OVERFLOW", file_overflow);

  envp = w_envp_make_from_ht(cmd->envht, &env_size);

  posix_spawnattr_init(&attr);
#ifndef _WIN32
  sigemptyset(&mask);
  posix_spawnattr_setsigmask(&attr, &mask);
#endif
  posix_spawnattr_setflags(&attr,
      POSIX_SPAWN_SETSIGMASK|
#ifdef POSIX_SPAWN_CLOEXEC_DEFAULT
      // Darwin: close everything except what we put in file actions
      POSIX_SPAWN_CLOEXEC_DEFAULT|
#endif
      POSIX_SPAWN_SETPGROUP);

  posix_spawn_file_actions_init(&actions);

#ifndef _WIN32
  posix_spawn_file_actions_adddup2(
      &actions, stdin_file->getFileDescriptor(), STDIN_FILENO);
#else
  posix_spawn_file_actions_adddup2_handle_np(
      &actions, stdin_file->getWindowsHandle(), STDIN_FILENO);
#endif
  if (cmd->stdout_name) {
    posix_spawn_file_actions_addopen(&actions, STDOUT_FILENO,
        cmd->stdout_name, cmd->stdout_flags, 0666);
  } else {
    posix_spawn_file_actions_adddup2(&actions, STDOUT_FILENO, STDOUT_FILENO);
  }

  if (cmd->stderr_name) {
    posix_spawn_file_actions_addopen(&actions, STDERR_FILENO,
        cmd->stderr_name, cmd->stderr_flags, 0666);
  } else {
    posix_spawn_file_actions_adddup2(&actions, STDERR_FILENO, STDERR_FILENO);
  }

  // Figure out the appropriate cwd
  {
    const char *cwd = NULL;
    working_dir = NULL;

    if (cmd->query->relative_root) {
      working_dir = cmd->query->relative_root;
    } else {
      working_dir = root->root_path;
    }
    w_string_addref(working_dir);

    json_unpack(cmd->definition, "{s:s}", "chdir", &cwd);
    if (cwd) {
      w_string_t *cwd_str = w_string_new_typed(cwd, W_STRING_BYTE);

      if (w_is_path_absolute_cstr(cwd)) {
        w_string_delref(working_dir);
        working_dir = cwd_str;
      } else {
        w_string_t *joined;

        joined = w_string_path_cat(working_dir, cwd_str);
        w_string_delref(cwd_str);
        w_string_delref(working_dir);

        working_dir = joined;
      }
    }

    w_log(W_LOG_DBG, "using %.*s for working dir\n", working_dir->len,
          working_dir->buf);
  }

#ifndef _WIN32
  // This mutex is present to avoid fighting over the cwd when multiple
  // triggers run at the same time.  It doesn't coordinate with all
  // possible chdir() calls, but this is the only place that we do this
  // in the watchman server process.
  static std::mutex cwdMutex;
  {
    std::unique_lock<std::mutex> lock(cwdMutex);
    ignore_result(chdir(working_dir->buf));
#else
    posix_spawnattr_setcwd_np(&attr, working_dir->buf);
#endif
    w_string_delref(working_dir);
    working_dir = nullptr;

    ret =
        posix_spawnp(&cmd->current_proc, argv[0], &actions, &attr, argv, envp);
    if (ret != 0) {
      // On Darwin (at least), posix_spawn can fail but will still populate the
      // pid.  Since we use the pid to gate future spawns, we need to ensure
      // that we clear out the pid on failure, otherwise the trigger would be
      // effectively disabled for the rest of the watch lifetime
      cmd->current_proc = 0;
    }
#ifndef _WIN32
    ignore_result(chdir("/"));
  }
#endif

  // If failed, we want to make sure we log enough info to figure out why
  result_log_level = res == 0 ? W_LOG_DBG : W_LOG_ERR;

  w_log(result_log_level, "posix_spawnp: %s\n", cmd->triggername.c_str());
  for (i = 0; argv[i]; i++) {
    w_log(result_log_level, "argv[%d] %s\n", i, argv[i]);
  }
  for (i = 0; envp[i]; i++) {
    w_log(result_log_level, "envp[%d] %s\n", i, envp[i]);
  }

  w_log(
      result_log_level,
      "trigger %s:%s pid=%d ret=%d %s\n",
      root->root_path.c_str(),
      cmd->triggername.c_str(),
      (int)cmd->current_proc,
      ret,
      strerror(ret));

  free(argv);
  free(envp);

  posix_spawnattr_destroy(&attr);
  posix_spawn_file_actions_destroy(&actions);
}