Import posix_spawn from Gnulib.

posix_spawn is less error-prone than vfork + exec, and can make use of
system-specific optimizations like `clone' on Linux.  Import Gnulib
replacement so that we can use recent additions like
`posix_spawn_file_actions_addchdir'.

The only manual change are to admin/merge-gnulib and .gitignore.  All
other changes are due to rerunning merge-gnulib.

* admin/merge-gnulib (GNULIB_MODULES): Add posix_spawn-related
modules.
* .gitignore: Add new generated files.

1 files changed, 56 insertions, 0 deletions

diff --git a/lib/spawn_faction_init.c b/lib/spawn_faction_init.c
new file mode 100644
index 00000000000..135605fb8c6
--- /dev/null
+++ b/lib/spawn_faction_init.c
@@ -0,0 +1,56 @@
+/* Copyright (C) 2000, 2009-2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <spawn.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "spawn_int.h"
+
+
+/* Function used to increase the size of the allocated array.  This
+   function is called from the 'add'-functions.  */
+int
+__posix_spawn_file_actions_realloc (posix_spawn_file_actions_t *file_actions)
+{
+  int newalloc = file_actions->_allocated + 8;
+  void *newmem = realloc (file_actions->_actions,
+                          newalloc * sizeof (struct __spawn_action));
+
+  if (newmem == NULL)
+    /* Not enough memory.  */
+    return ENOMEM;
+
+  file_actions->_actions = (struct __spawn_action *) newmem;
+  file_actions->_allocated = newalloc;
+
+  return 0;
+}
+
+
+/* Initialize data structure for file attribute for 'spawn' call.  */
+int
+posix_spawn_file_actions_init (posix_spawn_file_actions_t *file_actions)
+{
+  /* Simply clear all the elements.  */
+  memset (file_actions, '\0', sizeof (*file_actions));
+  return 0;
+}