Adding upstream version 1.21.upstream/1.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 674 insertions, 0 deletions

diff --git a/lib/spawn-pipe.c b/lib/spawn-pipe.c
new file mode 100644
index 0000000..768c8b6
--- /dev/null
+++ b/lib/spawn-pipe.c
@@ -0,0 +1,674 @@
+/* Creation of subprocesses, communicating via pipes.
+   Copyright (C) 2001-2004, 2006-2020 Free Software Foundation, Inc.
+   Written by Bruno Haible <haible@clisp.cons.org>, 2001.
+
+   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/>.  */
+
+
+/* Tell clang not to warn about the 'child' variable, below.  */
+#if defined __clang__
+# pragma clang diagnostic ignored "-Wconditional-uninitialized"
+#endif
+
+#include <config.h>
+
+/* Specification.  */
+#include "spawn-pipe.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "canonicalize.h"
+#include "error.h"
+#include "fatal-signal.h"
+#include "filename.h"
+#include "findprog.h"
+#include "unistd-safer.h"
+#include "wait-process.h"
+#include "xalloc.h"
+#include "gettext.h"
+
+#define _(str) gettext (str)
+
+
+/* Choice of implementation for native Windows.
+   - Define to 0 to use the posix_spawn facility (modules 'posix_spawn' and
+     'posix_spawnp'), that is based on the module 'windows-spawn'.
+   - Define to 1 to use the older code, that uses the module 'windows-spawn'
+     directly.
+   You can set this macro from a Makefile or at configure time, from the
+   CPPFLAGS.  */
+#ifndef SPAWN_PIPE_IMPL_AVOID_POSIX_SPAWN
+# define SPAWN_PIPE_IMPL_AVOID_POSIX_SPAWN 0
+#endif
+
+
+#if (defined _WIN32 && !defined __CYGWIN__) && SPAWN_PIPE_IMPL_AVOID_POSIX_SPAWN
+
+/* Native Windows API.  */
+# if GNULIB_MSVC_NOTHROW
+#  include "msvc-nothrow.h"
+# else
+#  include <io.h>
+# endif
+# include <process.h>
+# include "windows-spawn.h"
+
+#elif defined __KLIBC__
+
+/* OS/2 kLIBC API.  */
+# include <process.h>
+# include "os2-spawn.h"
+
+#else
+
+/* Unix API.  */
+# include <spawn.h>
+
+#endif
+
+
+#ifdef EINTR
+
+/* EINTR handling for close().
+   These functions can return -1/EINTR even though we don't have any
+   signal handlers set up, namely when we get interrupted via SIGSTOP.  */
+
+static int
+nonintr_close (int fd)
+{
+  int retval;
+
+  do
+    retval = close (fd);
+  while (retval < 0 && errno == EINTR);
+
+  return retval;
+}
+#undef close /* avoid warning related to gnulib module unistd */
+#define close nonintr_close
+
+#if (defined _WIN32 && !defined __CYGWIN__) && SPAWN_PIPE_IMPL_AVOID_POSIX_SPAWN
+static int
+nonintr_open (const char *pathname, int oflag, mode_t mode)
+{
+  int retval;
+
+  do
+    retval = open (pathname, oflag, mode);
+  while (retval < 0 && errno == EINTR);
+
+  return retval;
+}
+# undef open /* avoid warning on VMS */
+# define open nonintr_open
+#endif
+
+#endif
+
+
+/* Open a pipe connected to a child process.
+ *
+ *           write       system                read
+ *    parent  ->   fd[1]   ->   STDIN_FILENO    ->   child       if pipe_stdin
+ *    parent  <-   fd[0]   <-   STDOUT_FILENO   <-   child       if pipe_stdout
+ *           read        system                write
+ *
+ * At least one of pipe_stdin, pipe_stdout must be true.
+ * pipe_stdin and prog_stdin together determine the child's standard input.
+ * pipe_stdout and prog_stdout together determine the child's standard output.
+ * If pipe_stdin is true, prog_stdin is ignored.
+ * If pipe_stdout is true, prog_stdout is ignored.
+ */
+static pid_t
+create_pipe (const char *progname,
+             const char *prog_path,
+             const char * const *prog_argv,
+             const char *directory,
+             bool pipe_stdin, bool pipe_stdout,
+             const char *prog_stdin, const char *prog_stdout,
+             bool null_stderr,
+             bool slave_process, bool exit_on_error,
+             int fd[2])
+{
+  int saved_errno;
+  char *prog_path_to_free = NULL;
+
+  if (directory != NULL)
+    {
+      /* If a change of directory is requested, make sure PROG_PATH is absolute
+         before we do so.  This is needed because
+           - posix_spawn and posix_spawnp are required to resolve a relative
+             PROG_PATH *after* changing the directory.  See
+             <https://www.austingroupbugs.net/view.php?id=1208>:
+               "if this pathname does not start with a <slash> it shall be
+                interpreted relative to the working directory of the child
+                process _after_ all file_actions have been performed."
+             But this would be a surprising application behaviour, possibly
+             even security relevant.
+           - For the Windows CreateProcess() function, it is unspecified whether
+             a relative file name is interpreted to the parent's current
+             directory or to the specified directory.  See
+             <https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessa>  */
+      if (! IS_ABSOLUTE_FILE_NAME (prog_path))
+        {
+          const char *resolved_prog =
+            find_in_given_path (prog_path, getenv ("PATH"), NULL, false);
+          if (resolved_prog == NULL)
+            goto fail_with_errno;
+          if (resolved_prog != prog_path)
+            prog_path_to_free = (char *) resolved_prog;
+          prog_path = resolved_prog;
+
+          if (! IS_ABSOLUTE_FILE_NAME (prog_path))
+            {
+              char *absolute_prog =
+                canonicalize_filename_mode (prog_path, CAN_MISSING | CAN_NOLINKS);
+              if (absolute_prog == NULL)
+                {
+                  saved_errno = errno;
+                  free (prog_path_to_free);
+                  goto fail_with_saved_errno;
+                }
+              free (prog_path_to_free);
+              prog_path_to_free = absolute_prog;
+              prog_path = absolute_prog;
+
+              if (! IS_ABSOLUTE_FILE_NAME (prog_path))
+                abort ();
+            }
+        }
+    }
+
+#if ((defined _WIN32 && !defined __CYGWIN__) && SPAWN_PIPE_IMPL_AVOID_POSIX_SPAWN) || defined __KLIBC__
+
+  /* Native Windows API.
+     This uses _pipe(), dup2(), and _spawnv().  It could also be implemented
+     using the low-level functions CreatePipe(), DuplicateHandle(),
+     CreateProcess() and _open_osfhandle(); see the GNU make and GNU clisp
+     and cvs source code.  */
+  char *argv_mem_to_free;
+  int ifd[2];
+  int ofd[2];
+  int child;
+  int nulloutfd;
+  int stdinfd;
+  int stdoutfd;
+
+  const char **argv = prepare_spawn (prog_argv, &argv_mem_to_free);
+  if (argv == NULL)
+    xalloc_die ();
+
+  if (pipe_stdout)
+    if (pipe2_safer (ifd, O_BINARY | O_CLOEXEC) < 0)
+      error (EXIT_FAILURE, errno, _("cannot create pipe"));
+  if (pipe_stdin)
+    if (pipe2_safer (ofd, O_BINARY | O_CLOEXEC) < 0)
+      error (EXIT_FAILURE, errno, _("cannot create pipe"));
+/* Data flow diagram:
+ *
+ *           write        system         read
+ *    parent  ->   ofd[1]   ->   ofd[0]   ->   child       if pipe_stdin
+ *    parent  <-   ifd[0]   <-   ifd[1]   <-   child       if pipe_stdout
+ *           read         system         write
+ *
+ */
+
+  child = -1;
+
+# if (defined _WIN32 && !defined __CYGWIN__) && SPAWN_PIPE_IMPL_AVOID_POSIX_SPAWN
+  bool must_close_ifd1 = pipe_stdout;
+  bool must_close_ofd0 = pipe_stdin;
+
+  /* Create standard file handles of child process.  */
+  HANDLE stdin_handle = INVALID_HANDLE_VALUE;
+  HANDLE stdout_handle = INVALID_HANDLE_VALUE;
+  nulloutfd = -1;
+  stdinfd = -1;
+  stdoutfd = -1;
+  if ((!null_stderr
+       || (nulloutfd = open ("NUL", O_RDWR, 0)) >= 0)
+      && (pipe_stdin
+          || prog_stdin == NULL
+          || (stdinfd = open (prog_stdin, O_RDONLY, 0)) >= 0)
+      && (pipe_stdout
+          || prog_stdout == NULL
+          || (stdoutfd = open (prog_stdout, O_WRONLY, 0)) >= 0))
+    /* The child process doesn't inherit ifd[0], ifd[1], ofd[0], ofd[1],
+       but it inherits the three STD*_FILENO for which we pass the handles.  */
+    /* Pass the environment explicitly.  This is needed if the program has
+       modified the environment using putenv() or [un]setenv().  On Windows,
+       processes have two environments, one in the "environment block" of the
+       process and managed through SetEnvironmentVariable(), and one inside the
+       process, in the location retrieved by the 'environ' macro.  If we were
+       to pass NULL, the child process would inherit a copy of the environment
+       block - ignoring the effects of putenv() and [un]setenv().  */
+    {
+      stdin_handle =
+        (HANDLE) _get_osfhandle (pipe_stdin ? ofd[0] :
+                                 prog_stdin == NULL ? STDIN_FILENO : stdinfd);
+      if (pipe_stdin)
+        {
+          HANDLE curr_process = GetCurrentProcess ();
+          HANDLE duplicate;
+          if (!DuplicateHandle (curr_process, stdin_handle,
+                                curr_process, &duplicate,
+                                0, TRUE, DUPLICATE_SAME_ACCESS))
+            {
+              errno = EBADF; /* arbitrary */
+              goto failed;
+            }
+          must_close_ofd0 = false;
+          close (ofd[0]); /* implies CloseHandle (stdin_handle); */
+          stdin_handle = duplicate;
+        }
+      stdout_handle =
+        (HANDLE) _get_osfhandle (pipe_stdout ? ifd[1] :
+                                 prog_stdout == NULL ? STDOUT_FILENO : stdoutfd);
+      if (pipe_stdout)
+        {
+          HANDLE curr_process = GetCurrentProcess ();
+          HANDLE duplicate;
+          if (!DuplicateHandle (curr_process, stdout_handle,
+                                curr_process, &duplicate,
+                                0, TRUE, DUPLICATE_SAME_ACCESS))
+            {
+              errno = EBADF; /* arbitrary */
+              goto failed;
+            }
+          must_close_ifd1 = false;
+          close (ifd[1]); /* implies CloseHandle (stdout_handle); */
+          stdout_handle = duplicate;
+        }
+      HANDLE stderr_handle =
+        (HANDLE) _get_osfhandle (null_stderr ? nulloutfd : STDERR_FILENO);
+
+      child = spawnpvech (P_NOWAIT, prog_path, argv + 1,
+                          (const char * const *) environ, directory,
+                          stdin_handle, stdout_handle, stderr_handle);
+#  if 0 /* Executing arbitrary files as shell scripts is unsecure.  */
+      if (child == -1 && errno == ENOEXEC)
+        {
+          /* prog is not a native executable.  Try to execute it as a
+             shell script.  Note that prepare_spawn() has already prepended
+             a hidden element "sh.exe" to argv.  */
+          argv[1] = prog_path;
+          child = spawnpvech (P_NOWAIT, argv[0], argv,
+                              (const char * const *) environ, directory,
+                              stdin_handle, stdout_handle, stderr_handle);
+        }
+#  endif
+    }
+ failed:
+  if (child == -1)
+    saved_errno = errno;
+  if (stdinfd >= 0)
+    close (stdinfd);
+  if (stdoutfd >= 0)
+    close (stdoutfd);
+  if (nulloutfd >= 0)
+    close (nulloutfd);
+
+  if (pipe_stdin)
+    {
+      if (must_close_ofd0)
+        close (ofd[0]);
+      else
+        if (stdin_handle != INVALID_HANDLE_VALUE)
+          CloseHandle (stdin_handle);
+    }
+  if (pipe_stdout)
+    {
+      if (must_close_ifd1)
+        close (ifd[1]);
+      else
+        if (stdout_handle != INVALID_HANDLE_VALUE)
+          CloseHandle (stdout_handle);
+    }
+
+# else /* __KLIBC__ */
+  if (!(directory == NULL && strcmp (directory, ".") == 0))
+    {
+      /* A directory argument is not supported in this implementation.  */
+      saved_errno = EINVAL;
+      goto fail_with_saved_errno;
+    }
+
+  int orig_stdin;
+  int orig_stdout;
+  int orig_stderr;
+
+  /* Save standard file handles of parent process.  */
+  if (pipe_stdin || prog_stdin != NULL)
+    orig_stdin = dup_safer_noinherit (STDIN_FILENO);
+  if (pipe_stdout || prog_stdout != NULL)
+    orig_stdout = dup_safer_noinherit (STDOUT_FILENO);
+  if (null_stderr)
+    orig_stderr = dup_safer_noinherit (STDERR_FILENO);
+
+  /* Create standard file handles of child process.  */
+  nulloutfd = -1;
+  stdinfd = -1;
+  stdoutfd = -1;
+  if ((!pipe_stdin || dup2 (ofd[0], STDIN_FILENO) >= 0)
+      && (!pipe_stdout || dup2 (ifd[1], STDOUT_FILENO) >= 0)
+      && (!null_stderr
+          || ((nulloutfd = open ("NUL", O_RDWR, 0)) >= 0
+              && (nulloutfd == STDERR_FILENO
+                  || (dup2 (nulloutfd, STDERR_FILENO) >= 0
+                      && close (nulloutfd) >= 0))))
+      && (pipe_stdin
+          || prog_stdin == NULL
+          || ((stdinfd = open (prog_stdin, O_RDONLY, 0)) >= 0
+              && (stdinfd == STDIN_FILENO
+                  || (dup2 (stdinfd, STDIN_FILENO) >= 0
+                      && close (stdinfd) >= 0))))
+      && (pipe_stdout
+          || prog_stdout == NULL
+          || ((stdoutfd = open (prog_stdout, O_WRONLY, 0)) >= 0
+              && (stdoutfd == STDOUT_FILENO
+                  || (dup2 (stdoutfd, STDOUT_FILENO) >= 0
+                      && close (stdoutfd) >= 0)))))
+    /* The child process doesn't inherit ifd[0], ifd[1], ofd[0], ofd[1],
+       but it inherits all open()ed or dup2()ed file handles (which is what
+       we want in the case of STD*_FILENO).  */
+    {
+      child = _spawnvpe (P_NOWAIT, prog_path, argv + 1,
+                         (const char **) environ);
+#  if 0 /* Executing arbitrary files as shell scripts is unsecure.  */
+      if (child == -1 && errno == ENOEXEC)
+        {
+          /* prog is not a native executable.  Try to execute it as a
+             shell script.  Note that prepare_spawn() has already prepended
+             a hidden element "sh.exe" to argv.  */
+          child = _spawnvpe (P_NOWAIT, argv[0], argv,
+                             (const char **) environ);
+        }
+#  endif
+    }
+  if (child == -1)
+    saved_errno = errno;
+  if (stdinfd >= 0)
+    close (stdinfd);
+  if (stdoutfd >= 0)
+    close (stdoutfd);
+  if (nulloutfd >= 0)
+    close (nulloutfd);
+
+  /* Restore standard file handles of parent process.  */
+  if (null_stderr)
+    undup_safer_noinherit (orig_stderr, STDERR_FILENO);
+  if (pipe_stdout || prog_stdout != NULL)
+    undup_safer_noinherit (orig_stdout, STDOUT_FILENO);
+  if (pipe_stdin || prog_stdin != NULL)
+    undup_safer_noinherit (orig_stdin, STDIN_FILENO);
+
+  if (pipe_stdin)
+    close (ofd[0]);
+  if (pipe_stdout)
+    close (ifd[1]);
+# endif
+
+  free (argv);
+  free (argv_mem_to_free);
+  free (prog_path_to_free);
+
+  if (child == -1)
+    {
+      if (pipe_stdout)
+        close (ifd[0]);
+      if (pipe_stdin)
+        close (ofd[1]);
+      goto fail_with_saved_errno;
+    }
+
+  if (pipe_stdout)
+    fd[0] = ifd[0];
+  if (pipe_stdin)
+    fd[1] = ofd[1];
+  return child;
+
+#else
+
+  /* Unix API.  */
+  int ifd[2];
+  int ofd[2];
+  sigset_t blocked_signals;
+  posix_spawn_file_actions_t actions;
+  bool actions_allocated;
+  posix_spawnattr_t attrs;
+  bool attrs_allocated;
+  int err;
+  pid_t child;
+
+  if (pipe_stdout)
+    if (pipe_safer (ifd) < 0)
+      error (EXIT_FAILURE, errno, _("cannot create pipe"));
+  if (pipe_stdin)
+    if (pipe_safer (ofd) < 0)
+      error (EXIT_FAILURE, errno, _("cannot create pipe"));
+/* Data flow diagram:
+ *
+ *           write        system         read
+ *    parent  ->   ofd[1]   ->   ofd[0]   ->   child       if pipe_stdin
+ *    parent  <-   ifd[0]   <-   ifd[1]   <-   child       if pipe_stdout
+ *           read         system         write
+ *
+ */
+
+  if (slave_process)
+    {
+      sigprocmask (SIG_SETMASK, NULL, &blocked_signals);
+      block_fatal_signals ();
+    }
+  actions_allocated = false;
+  attrs_allocated = false;
+  if ((err = posix_spawn_file_actions_init (&actions)) != 0
+      || (actions_allocated = true,
+          (pipe_stdin
+           && (err = posix_spawn_file_actions_adddup2 (&actions,
+                                                       ofd[0], STDIN_FILENO))
+              != 0)
+          || (pipe_stdout
+              && (err = posix_spawn_file_actions_adddup2 (&actions,
+                                                          ifd[1], STDOUT_FILENO))
+                 != 0)
+          || (pipe_stdin
+              && (err = posix_spawn_file_actions_addclose (&actions, ofd[0]))
+                 != 0)
+          || (pipe_stdout
+              && (err = posix_spawn_file_actions_addclose (&actions, ifd[1]))
+                 != 0)
+          || (pipe_stdin
+              && (err = posix_spawn_file_actions_addclose (&actions, ofd[1]))
+                 != 0)
+          || (pipe_stdout
+              && (err = posix_spawn_file_actions_addclose (&actions, ifd[0]))
+                 != 0)
+          || (null_stderr
+              && (err = posix_spawn_file_actions_addopen (&actions,
+                                                          STDERR_FILENO,
+                                                          "/dev/null", O_RDWR,
+                                                          0))
+                 != 0)
+          || (!pipe_stdin
+              && prog_stdin != NULL
+              && (err = posix_spawn_file_actions_addopen (&actions,
+                                                          STDIN_FILENO,
+                                                          prog_stdin, O_RDONLY,
+                                                          0))
+                 != 0)
+          || (!pipe_stdout
+              && prog_stdout != NULL
+              && (err = posix_spawn_file_actions_addopen (&actions,
+                                                          STDOUT_FILENO,
+                                                          prog_stdout, O_WRONLY,
+                                                          0))
+                 != 0)
+          || (directory != NULL
+              && (err = posix_spawn_file_actions_addchdir (&actions,
+                                                           directory)))
+          || (slave_process
+              && ((err = posix_spawnattr_init (&attrs)) != 0
+                  || (attrs_allocated = true,
+# if defined _WIN32 && !defined __CYGWIN__
+                      (err = posix_spawnattr_setpgroup (&attrs, 0)) != 0
+                      || (err = posix_spawnattr_setflags (&attrs,
+                                                         POSIX_SPAWN_SETPGROUP))
+                         != 0
+# else
+                      (err = posix_spawnattr_setsigmask (&attrs,
+                                                         &blocked_signals))
+                      != 0
+                      || (err = posix_spawnattr_setflags (&attrs,
+                                                        POSIX_SPAWN_SETSIGMASK))
+                         != 0
+# endif
+             )   )   )
+          || (err = (directory != NULL
+                     ? posix_spawn (&child, prog_path, &actions,
+                                    attrs_allocated ? &attrs : NULL,
+                                    (char * const *) prog_argv, environ)
+                     : posix_spawnp (&child, prog_path, &actions,
+                                     attrs_allocated ? &attrs : NULL,
+                                     (char * const *) prog_argv, environ)))
+             != 0))
+    {
+      if (actions_allocated)
+        posix_spawn_file_actions_destroy (&actions);
+      if (attrs_allocated)
+        posix_spawnattr_destroy (&attrs);
+      if (slave_process)
+        unblock_fatal_signals ();
+      if (pipe_stdout)
+        {
+          close (ifd[0]);
+          close (ifd[1]);
+        }
+      if (pipe_stdin)
+        {
+          close (ofd[0]);
+          close (ofd[1]);
+        }
+      free (prog_path_to_free);
+      saved_errno = err;
+      goto fail_with_saved_errno;
+    }
+  posix_spawn_file_actions_destroy (&actions);
+  if (attrs_allocated)
+    posix_spawnattr_destroy (&attrs);
+  if (slave_process)
+    {
+      register_slave_subprocess (child);
+      unblock_fatal_signals ();
+    }
+  if (pipe_stdin)
+    close (ofd[0]);
+  if (pipe_stdout)
+    close (ifd[1]);
+  free (prog_path_to_free);
+
+  if (pipe_stdout)
+    fd[0] = ifd[0];
+  if (pipe_stdin)
+    fd[1] = ofd[1];
+  return child;
+
+#endif
+
+ fail_with_errno:
+  saved_errno = errno;
+ fail_with_saved_errno:
+  if (exit_on_error || !null_stderr)
+    error (exit_on_error ? EXIT_FAILURE : 0, saved_errno,
+           _("%s subprocess failed"), progname);
+  errno = saved_errno;
+  return -1;
+}
+
+/* Open a bidirectional pipe.
+ *
+ *           write       system                read
+ *    parent  ->   fd[1]   ->   STDIN_FILENO    ->   child
+ *    parent  <-   fd[0]   <-   STDOUT_FILENO   <-   child
+ *           read        system                write
+ *
+ */
+pid_t
+create_pipe_bidi (const char *progname,
+                  const char *prog_path, const char * const *prog_argv,
+                  const char *directory,
+                  bool null_stderr,
+                  bool slave_process, bool exit_on_error,
+                  int fd[2])
+{
+  pid_t result = create_pipe (progname, prog_path, prog_argv, directory,
+                              true, true, NULL, NULL,
+                              null_stderr, slave_process, exit_on_error,
+                              fd);
+  return result;
+}
+
+/* Open a pipe for input from a child process.
+ * The child's stdin comes from a file.
+ *
+ *           read        system                write
+ *    parent  <-   fd[0]   <-   STDOUT_FILENO   <-   child
+ *
+ */
+pid_t
+create_pipe_in (const char *progname,
+                const char *prog_path, const char * const *prog_argv,
+                const char *directory,
+                const char *prog_stdin, bool null_stderr,
+                bool slave_process, bool exit_on_error,
+                int fd[1])
+{
+  int iofd[2];
+  pid_t result = create_pipe (progname, prog_path, prog_argv, directory,
+                              false, true, prog_stdin, NULL,
+                              null_stderr, slave_process, exit_on_error,
+                              iofd);
+  if (result != -1)
+    fd[0] = iofd[0];
+  return result;
+}
+
+/* Open a pipe for output to a child process.
+ * The child's stdout goes to a file.
+ *
+ *           write       system                read
+ *    parent  ->   fd[0]   ->   STDIN_FILENO    ->   child
+ *
+ */
+pid_t
+create_pipe_out (const char *progname,
+                 const char *prog_path, const char * const *prog_argv,
+                 const char *directory,
+                 const char *prog_stdout, bool null_stderr,
+                 bool slave_process, bool exit_on_error,
+                 int fd[1])
+{
+  int iofd[2];
+  pid_t result = create_pipe (progname, prog_path, prog_argv, directory,
+                              true, false, NULL, prog_stdout,
+                              null_stderr, slave_process, exit_on_error,
+                              iofd);
+  if (result != -1)
+    fd[0] = iofd[1];
+  return result;
+}