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gspawn: Handle arbitrary FD passing and renumbering between fork/exec
This effectively moves some of the functionality of `GSubprocess` (`g_subprocess_launcher_take_fd()`) into `g_spawn*()`, which should make implementation a little simpler. Signed-off-by: Philip Withnall <pwithnall@endlessos.org> Helps: #2097
This commit is contained in:
Philip Withnall
parent
cddcd24b52
commit
7be9767cc4
137
glib/gspawn.c
137
glib/gspawn.c
@ -188,6 +188,9 @@ static gboolean fork_exec (gboolean intermediate_child,
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gint stdin_fd,
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gint stdout_fd,
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gint stderr_fd,
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const gint *source_fds,
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const gint *target_fds,
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gsize n_fds,
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GError **error);
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G_DEFINE_QUARK (g-exec-error-quark, g_spawn_error)
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@ -413,6 +416,7 @@ g_spawn_sync (const gchar *working_directory,
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standard_output ? &outpipe : NULL,
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standard_error ? &errpipe : NULL,
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-1, -1, -1,
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NULL, NULL, 0,
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error))
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return FALSE;
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@ -801,6 +805,7 @@ g_spawn_async_with_pipes (const gchar *working_directory,
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standard_output,
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standard_error,
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-1, -1, -1,
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NULL, NULL, 0,
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error);
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}
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@ -882,6 +887,7 @@ g_spawn_async_with_fds (const gchar *working_directory,
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stdin_fd,
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stdout_fd,
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stderr_fd,
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NULL, NULL, 0,
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error);
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}
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@ -1133,6 +1139,68 @@ set_cloexec (void *data, gint fd)
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return 0;
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}
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/* This function is called between fork() and exec() and hence must be
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* async-signal-safe (see signal-safety(7)). */
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static void
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unset_cloexec (int fd)
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{
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int flags;
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int result;
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flags = fcntl (fd, F_GETFD, 0);
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if (flags != -1)
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{
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int errsv;
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flags &= (~FD_CLOEXEC);
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do
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{
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result = fcntl (fd, F_SETFD, flags);
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errsv = errno;
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}
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while (result == -1 && errsv == EINTR);
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}
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}
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/* This function is called between fork() and exec() and hence must be
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* async-signal-safe (see signal-safety(7)). */
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static int
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dupfd_cloexec (int parent_fd)
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{
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int fd, errsv;
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#ifdef F_DUPFD_CLOEXEC
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do
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{
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fd = fcntl (parent_fd, F_DUPFD_CLOEXEC, 3);
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errsv = errno;
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}
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while (fd == -1 && errsv == EINTR);
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#else
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/* OS X Snow Lion and earlier don't have F_DUPFD_CLOEXEC:
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* https://bugzilla.gnome.org/show_bug.cgi?id=710962
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*/
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int result, flags;
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do
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{
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fd = fcntl (parent_fd, F_DUPFD, 3);
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errsv = errno;
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}
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while (fd == -1 && errsv == EINTR);
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flags = fcntl (fd, F_GETFD, 0);
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if (flags != -1)
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{
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flags |= FD_CLOEXEC;
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do
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{
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result = fcntl (fd, F_SETFD, flags);
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errsv = errno;
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}
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while (result == -1 && errsv == EINTR);
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}
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#endif
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return fd;
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}
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/* This function is called between fork() and exec() and hence must be
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* async-signal-safe (see signal-safety(7)). */
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static gint
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@ -1382,6 +1450,9 @@ do_exec (gint child_err_report_fd,
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gint stdin_fd,
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gint stdout_fd,
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gint stderr_fd,
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gint *source_fds,
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const gint *target_fds,
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gsize n_fds,
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const gchar *working_directory,
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const gchar * const *argv,
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gchar **argv_buffer,
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@ -1398,6 +1469,8 @@ do_exec (gint child_err_report_fd,
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GSpawnChildSetupFunc child_setup,
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gpointer user_data)
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{
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gsize i;
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if (working_directory && chdir (working_directory) < 0)
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write_err_and_exit (child_err_report_fd,
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CHILD_CHDIR_FAILED);
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@ -1461,14 +1534,14 @@ do_exec (gint child_err_report_fd,
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close_and_invalidate (&write_null);
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}
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/* Close all file descriptors but stdin, stdout and stderr
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/* Close all file descriptors but stdin, stdout and stderr, and any of source_fds,
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* before we exec. Note that this includes
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* child_err_report_fd, which keeps the parent from blocking
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* forever on the other end of that pipe.
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*/
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if (close_descriptors)
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{
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if (child_setup == NULL)
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if (child_setup == NULL && n_fds == 0)
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{
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safe_dup2 (child_err_report_fd, 3);
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set_cloexec (GINT_TO_POINTER (0), 3);
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@ -1485,7 +1558,44 @@ do_exec (gint child_err_report_fd,
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/* We need to do child_err_report_fd anyway */
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set_cloexec (GINT_TO_POINTER (0), child_err_report_fd);
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}
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/*
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* Work through the @source_fds and @target_fds mapping.
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*
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* Based on code derived from
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* gnome-terminal:src/terminal-screen.c:terminal_screen_child_setup(),
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* used under the LGPLv2+ with permission from author.
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*/
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/* Basic fd assignments (where source == target) we can just unset FD_CLOEXEC
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*
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* If we're doing remapping fd assignments, we need to handle
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* the case where the user has specified e.g.:
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* 5 -> 4, 4 -> 6
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*
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* We do this by duping the source fds temporarily in a first pass.
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*/
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if (n_fds > 0)
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{
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for (i = 0; i < n_fds; i++)
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{
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if (source_fds[i] != target_fds[i])
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source_fds[i] = dupfd_cloexec (source_fds[i]);
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}
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for (i = 0; i < n_fds; i++)
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{
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if (source_fds[i] == target_fds[i])
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{
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unset_cloexec (source_fds[i]);
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}
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else
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{
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safe_dup2 (source_fds[i], target_fds[i]);
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(void) close (source_fds[i]);
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}
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}
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}
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/* Call user function just before we exec */
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if (child_setup)
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{
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@ -1752,6 +1862,9 @@ fork_exec (gboolean intermediate_child,
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gint stdin_fd,
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gint stdout_fd,
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gint stderr_fd,
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const gint *source_fds,
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const gint *target_fds,
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gsize n_fds,
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GError **error)
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{
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GPid pid = -1;
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@ -1771,6 +1884,7 @@ fork_exec (gboolean intermediate_child,
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gint stderr_pipe[2] = { -1, -1 };
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gint child_close_fds[4] = { -1, -1, -1, -1 };
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gint n_child_close_fds = 0;
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gint *source_fds_copy = NULL;
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g_assert (stdin_pipe_out == NULL || stdin_fd < 0);
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g_assert (stdout_pipe_out == NULL || stdout_fd < 0);
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@ -1804,8 +1918,10 @@ fork_exec (gboolean intermediate_child,
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child_close_fds[n_child_close_fds++] = -1;
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#ifdef POSIX_SPAWN_AVAILABLE
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/* FIXME: Handle @source_fds and @target_fds in do_posix_spawn() using the
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* file actions API. */
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if (!intermediate_child && working_directory == NULL && !close_descriptors &&
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!search_path_from_envp && child_setup == NULL)
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!search_path_from_envp && child_setup == NULL && n_fds == 0)
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{
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g_trace_mark (G_TRACE_CURRENT_TIME, 0,
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"GLib", "posix_spawn",
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@ -1928,6 +2044,11 @@ fork_exec (gboolean intermediate_child,
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argv_buffer = argv_buffer_heap;
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}
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/* And one to hold a copy of @source_fds for later manipulation in do_exec(). */
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source_fds_copy = g_new (int, n_fds);
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if (n_fds > 0)
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memcpy (source_fds_copy, source_fds, sizeof (*source_fds) * n_fds);
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if (!g_unix_open_pipe (child_err_report_pipe, pipe_flags, error))
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goto cleanup_and_fail;
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@ -2005,6 +2126,9 @@ fork_exec (gboolean intermediate_child,
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stdin_fd,
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stdout_fd,
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stderr_fd,
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source_fds_copy,
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target_fds,
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n_fds,
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working_directory,
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argv,
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argv_buffer,
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@ -2038,6 +2162,9 @@ fork_exec (gboolean intermediate_child,
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stdin_fd,
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stdout_fd,
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stderr_fd,
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source_fds_copy,
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target_fds,
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n_fds,
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working_directory,
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argv,
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argv_buffer,
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@ -2175,6 +2302,7 @@ fork_exec (gboolean intermediate_child,
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g_free (search_path_buffer_heap);
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g_free (argv_buffer_heap);
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g_free (source_fds_copy);
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if (child_pid)
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*child_pid = pid;
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@ -2233,6 +2361,7 @@ success:
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g_clear_pointer (&search_path_buffer_heap, g_free);
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g_clear_pointer (&argv_buffer_heap, g_free);
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g_clear_pointer (&source_fds_copy, g_free);
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return FALSE;
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}
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