[glib: 8/15] gspawn: Add new g_spawn_async_with_pipes_and_fds() API
- From: Philip Withnall <pwithnall src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib: 8/15] gspawn: Add new g_spawn_async_with_pipes_and_fds() API
- Date: Tue, 16 Feb 2021 14:04:40 +0000 (UTC)
commit b31f3f5f806b2185ca15328e30f5d255de23be67
Author: Philip Withnall <pwithnall endlessos org>
Date: Tue Oct 13 13:39:36 2020 +0100
gspawn: Add new g_spawn_async_with_pipes_and_fds() API
This is a simple wrapper around the new source/target FD mapping
functionality in `fork_exec()`.
Signed-off-by: Philip Withnall <pwithnall endlessos org>
Helps: #2097
docs/reference/glib/glib-sections.txt | 1 +
glib/gspawn.c | 194 +++++++++++++++++++++++++---------
glib/gspawn.h | 19 ++++
glib/tests/spawn-singlethread.c | 71 +++++++++++++
4 files changed, 234 insertions(+), 51 deletions(-)
---
diff --git a/docs/reference/glib/glib-sections.txt b/docs/reference/glib/glib-sections.txt
index 1f27ec501..460a299bf 100644
--- a/docs/reference/glib/glib-sections.txt
+++ b/docs/reference/glib/glib-sections.txt
@@ -1527,6 +1527,7 @@ GSpawnFlags
GSpawnChildSetupFunc
g_spawn_async_with_fds
g_spawn_async_with_pipes
+g_spawn_async_with_pipes_and_fds
g_spawn_async
g_spawn_sync
G_SPAWN_EXIT_ERROR
diff --git a/glib/gspawn.c b/glib/gspawn.c
index 5e7c58700..b45e774d4 100644
--- a/glib/gspawn.c
+++ b/glib/gspawn.c
@@ -595,6 +595,82 @@ g_spawn_sync (const gchar *working_directory,
* @standard_error: (out) (optional): return location for file descriptor to read child's stderr, or %NULL
* @error: return location for error
*
+ * Identical to g_spawn_async_with_pipes_and_fds() but with `n_fds` set to zero,
+ * so no FD assignments are used.
+ *
+ * Returns: %TRUE on success, %FALSE if an error was set
+ */
+gboolean
+g_spawn_async_with_pipes (const gchar *working_directory,
+ gchar **argv,
+ gchar **envp,
+ GSpawnFlags flags,
+ GSpawnChildSetupFunc child_setup,
+ gpointer user_data,
+ GPid *child_pid,
+ gint *standard_input,
+ gint *standard_output,
+ gint *standard_error,
+ GError **error)
+{
+ g_return_val_if_fail (argv != NULL, FALSE);
+ g_return_val_if_fail (standard_output == NULL ||
+ !(flags & G_SPAWN_STDOUT_TO_DEV_NULL), FALSE);
+ g_return_val_if_fail (standard_error == NULL ||
+ !(flags & G_SPAWN_STDERR_TO_DEV_NULL), FALSE);
+ /* can't inherit stdin if we have an input pipe. */
+ g_return_val_if_fail (standard_input == NULL ||
+ !(flags & G_SPAWN_CHILD_INHERITS_STDIN), FALSE);
+
+ return fork_exec (!(flags & G_SPAWN_DO_NOT_REAP_CHILD),
+ working_directory,
+ (const gchar * const *) argv,
+ (const gchar * const *) envp,
+ !(flags & G_SPAWN_LEAVE_DESCRIPTORS_OPEN),
+ (flags & G_SPAWN_SEARCH_PATH) != 0,
+ (flags & G_SPAWN_SEARCH_PATH_FROM_ENVP) != 0,
+ (flags & G_SPAWN_STDOUT_TO_DEV_NULL) != 0,
+ (flags & G_SPAWN_STDERR_TO_DEV_NULL) != 0,
+ (flags & G_SPAWN_CHILD_INHERITS_STDIN) != 0,
+ (flags & G_SPAWN_FILE_AND_ARGV_ZERO) != 0,
+ (flags & G_SPAWN_CLOEXEC_PIPES) != 0,
+ child_setup,
+ user_data,
+ child_pid,
+ standard_input,
+ standard_output,
+ standard_error,
+ -1, -1, -1,
+ NULL, NULL, 0,
+ error);
+}
+
+/**
+ * g_spawn_async_with_pipes_and_fds:
+ * @working_directory: (type filename) (nullable): child's current working
+ * directory, or %NULL to inherit parent's, in the GLib file name encoding
+ * @argv: (array zero-terminated=1) (element-type filename): child's argument
+ * vector, in the GLib file name encoding
+ * @envp: (array zero-terminated=1) (element-type filename) (nullable):
+ * child's environment, or %NULL to inherit parent's, in the GLib file
+ * name encoding
+ * @flags: flags from #GSpawnFlags
+ * @child_setup: (scope async) (nullable): function to run in the child just before `exec()`
+ * @user_data: (closure): user data for @child_setup
+ * @stdin_fd: file descriptor to use for child's stdin, or `-1`
+ * @stdout_fd: file descriptor to use for child's stdout, or `-1`
+ * @stderr_fd: file descriptor to use for child's stderr, or `-1`
+ * @source_fds: (array length=n_fds) (nullable): array of FDs from the parent
+ * process to make available in the child process
+ * @target_fds: (array length=n_fds) (nullable): array of FDs to remap
+ * @source_fds to in the child process
+ * @n_fds: number of FDs in @source_fds and @target_fds
+ * @child_pid_out: (out) (optional): return location for child process ID, or %NULL
+ * @stdin_pipe_out: (out) (optional): return location for file descriptor to write to child's stdin, or %NULL
+ * @stdout_pipe_out: (out) (optional): return location for file descriptor to read child's stdout, or %NULL
+ * @stderr_pipe_out: (out) (optional): return location for file descriptor to read child's stderr, or %NULL
+ * @error: return location for error
+ *
* Executes a child program asynchronously (your program will not
* block waiting for the child to exit). The child program is
* specified by the only argument that must be provided, @argv.
@@ -674,14 +750,30 @@ g_spawn_sync (const gchar *working_directory,
* @envp. If both %G_SPAWN_SEARCH_PATH and %G_SPAWN_SEARCH_PATH_FROM_ENVP
* are used, the value from @envp takes precedence over the environment.
* %G_SPAWN_STDOUT_TO_DEV_NULL means that the child's standard output
- * will be discarded, instead of going to the same location as the parent's
- * standard output. If you use this flag, @standard_output must be %NULL.
+ * will be discarded, instead of going to the same location as the parent's
+ * standard output. If you use this flag, @stdout_pipe_out must be %NULL.
+ *
* %G_SPAWN_STDERR_TO_DEV_NULL means that the child's standard error
* will be discarded, instead of going to the same location as the parent's
- * standard error. If you use this flag, @standard_error must be %NULL.
+ * standard error. If you use this flag, @stderr_pipe_out must be %NULL.
+ *
* %G_SPAWN_CHILD_INHERITS_STDIN means that the child will inherit the parent's
* standard input (by default, the child's standard input is attached to
- * `/dev/null`). If you use this flag, @standard_input must be %NULL.
+ * `/dev/null`). If you use this flag, @stdin_pipe_out must be %NULL.
+ *
+ * It is valid to pass the same FD in multiple parameters (e.g. you can pass
+ * a single FD for both @stdout_fd and @stderr_fd, and include it in
+ * @source_fds too).
+ *
+ * @source_fds and @target_fds allow zero or more FDs from this process to be
+ * remapped to different FDs in the spawned process. If @n_fds is greater than
+ * zero, @source_fds and @target_fds must both be non-%NULL and the same length.
+ * Each FD in @source_fds is remapped to the FD number at the same index in
+ * @target_fds. The source and target FD may be equal to simply propagate an FD
+ * to the spawned process. FD remappings are processed after standard FDs, so
+ * any target FDs which equal @stdin_fd, @stdout_fd or @stderr_fd will overwrite
+ * them in the spawned process.
+ *
* %G_SPAWN_FILE_AND_ARGV_ZERO means that the first element of @argv is
* the file to execute, while the remaining elements are the actual
* argument vector to pass to the file. Normally g_spawn_async_with_pipes()
@@ -711,22 +803,22 @@ g_spawn_sync (const gchar *working_directory,
* GetExitCodeProcess(). You should close the handle with CloseHandle()
* or g_spawn_close_pid() when you no longer need it.
*
- * If non-%NULL, the @standard_input, @standard_output, @standard_error
+ * If non-%NULL, the @stdin_pipe_out, @stdout_pipe_out, @stderr_pipe_out
* locations will be filled with file descriptors for writing to the child's
* standard input or reading from its standard output or standard error.
* The caller of g_spawn_async_with_pipes() must close these file descriptors
* when they are no longer in use. If these parameters are %NULL, the
* corresponding pipe won't be created.
*
- * If @standard_input is %NULL, the child's standard input is attached to
+ * If @stdin_pipe_out is %NULL, the child's standard input is attached to
* `/dev/null` unless %G_SPAWN_CHILD_INHERITS_STDIN is set.
*
- * If @standard_error is NULL, the child's standard error goes to the same
- * location as the parent's standard error unless %G_SPAWN_STDERR_TO_DEV_NULL
+ * If @stderr_pipe_out is NULL, the child's standard error goes to the same
+ * location as the parent's standard error unless %G_SPAWN_STDERR_TO_DEV_NULL
* is set.
*
- * If @standard_output is NULL, the child's standard output goes to the same
- * location as the parent's standard output unless %G_SPAWN_STDOUT_TO_DEV_NULL
+ * If @stdout_pipe_out is NULL, the child's standard output goes to the same
+ * location as the parent's standard output unless %G_SPAWN_STDOUT_TO_DEV_NULL
* is set.
*
* @error can be %NULL to ignore errors, or non-%NULL to report errors.
@@ -736,8 +828,8 @@ g_spawn_sync (const gchar *working_directory,
* errors should be displayed to users. Possible errors are those from
* the #G_SPAWN_ERROR domain.
*
- * If an error occurs, @child_pid, @standard_input, @standard_output,
- * and @standard_error will not be filled with valid values.
+ * If an error occurs, @child_pid, @stdin_pipe_out, @stdout_pipe_out,
+ * and @stderr_pipe_out will not be filled with valid values.
*
* If @child_pid is not %NULL and an error does not occur then the returned
* process reference must be closed using g_spawn_close_pid().
@@ -763,29 +855,41 @@ g_spawn_sync (const gchar *working_directory,
* #GAppLaunchContext, or set the %DISPLAY environment variable.
*
* Returns: %TRUE on success, %FALSE if an error was set
+ *
+ * Since: 2.68
*/
gboolean
-g_spawn_async_with_pipes (const gchar *working_directory,
- gchar **argv,
- gchar **envp,
- GSpawnFlags flags,
- GSpawnChildSetupFunc child_setup,
- gpointer user_data,
- GPid *child_pid,
- gint *standard_input,
- gint *standard_output,
- gint *standard_error,
- GError **error)
+g_spawn_async_with_pipes_and_fds (const gchar *working_directory,
+ const gchar * const *argv,
+ const gchar * const *envp,
+ GSpawnFlags flags,
+ GSpawnChildSetupFunc child_setup,
+ gpointer user_data,
+ gint stdin_fd,
+ gint stdout_fd,
+ gint stderr_fd,
+ const gint *source_fds,
+ const gint *target_fds,
+ gsize n_fds,
+ GPid *child_pid_out,
+ gint *stdin_pipe_out,
+ gint *stdout_pipe_out,
+ gint *stderr_pipe_out,
+ GError **error)
{
g_return_val_if_fail (argv != NULL, FALSE);
- g_return_val_if_fail (standard_output == NULL ||
+ g_return_val_if_fail (stdout_pipe_out == NULL ||
!(flags & G_SPAWN_STDOUT_TO_DEV_NULL), FALSE);
- g_return_val_if_fail (standard_error == NULL ||
+ g_return_val_if_fail (stderr_pipe_out == NULL ||
!(flags & G_SPAWN_STDERR_TO_DEV_NULL), FALSE);
/* can't inherit stdin if we have an input pipe. */
- g_return_val_if_fail (standard_input == NULL ||
+ g_return_val_if_fail (stdin_pipe_out == NULL ||
!(flags & G_SPAWN_CHILD_INHERITS_STDIN), FALSE);
-
+ /* can’t use pipes and stdin/stdout/stderr FDs */
+ g_return_val_if_fail (stdin_pipe_out == NULL || stdin_fd < 0, FALSE);
+ g_return_val_if_fail (stdout_pipe_out == NULL || stdout_fd < 0, FALSE);
+ g_return_val_if_fail (stderr_pipe_out == NULL || stderr_fd < 0, FALSE);
+
return fork_exec (!(flags & G_SPAWN_DO_NOT_REAP_CHILD),
working_directory,
(const gchar * const *) argv,
@@ -800,12 +904,16 @@ g_spawn_async_with_pipes (const gchar *working_directory,
(flags & G_SPAWN_CLOEXEC_PIPES) != 0,
child_setup,
user_data,
- child_pid,
- standard_input,
- standard_output,
- standard_error,
- -1, -1, -1,
- NULL, NULL, 0,
+ child_pid_out,
+ stdin_pipe_out,
+ stdout_pipe_out,
+ stderr_pipe_out,
+ stdin_fd,
+ stdout_fd,
+ stderr_fd,
+ source_fds,
+ target_fds,
+ n_fds,
error);
}
@@ -823,24 +931,8 @@ g_spawn_async_with_pipes (const gchar *working_directory,
* @stderr_fd: file descriptor to use for child's stderr, or -1
* @error: return location for error
*
- * Identical to g_spawn_async_with_pipes() but instead of
- * creating pipes for the stdin/stdout/stderr, you can pass existing
- * file descriptors into this function through the @stdin_fd,
- * @stdout_fd and @stderr_fd parameters. The following @flags
- * also have their behaviour slightly tweaked as a result:
- *
- * %G_SPAWN_STDOUT_TO_DEV_NULL means that the child's standard output
- * will be discarded, instead of going to the same location as the parent's
- * standard output. If you use this flag, @standard_output must be -1.
- * %G_SPAWN_STDERR_TO_DEV_NULL means that the child's standard error
- * will be discarded, instead of going to the same location as the parent's
- * standard error. If you use this flag, @standard_error must be -1.
- * %G_SPAWN_CHILD_INHERITS_STDIN means that the child will inherit the parent's
- * standard input (by default, the child's standard input is attached to
- * /dev/null). If you use this flag, @standard_input must be -1.
- *
- * It is valid to pass the same fd in multiple parameters (e.g. you can pass
- * a single fd for both stdout and stderr).
+ * Identical to g_spawn_async_with_pipes_and_fds() but with `n_fds` set to zero,
+ * so no FD assignments are used.
*
* Returns: %TRUE on success, %FALSE if an error was set
*
diff --git a/glib/gspawn.h b/glib/gspawn.h
index f91453a3c..e09dc2aec 100644
--- a/glib/gspawn.h
+++ b/glib/gspawn.h
@@ -213,6 +213,25 @@ gboolean g_spawn_async_with_pipes (const gchar *working_directory,
gint *standard_error,
GError **error);
+GLIB_AVAILABLE_IN_2_68
+gboolean g_spawn_async_with_pipes_and_fds (const gchar *working_directory,
+ const gchar * const *argv,
+ const gchar * const *envp,
+ GSpawnFlags flags,
+ GSpawnChildSetupFunc child_setup,
+ gpointer user_data,
+ gint stdin_fd,
+ gint stdout_fd,
+ gint stderr_fd,
+ const gint *source_fds,
+ const gint *target_fds,
+ gsize n_fds,
+ GPid *child_pid_out,
+ gint *stdin_pipe_out,
+ gint *stdout_pipe_out,
+ gint *stderr_pipe_out,
+ GError **error);
+
/* Lets you provide fds for stdin/stdout/stderr */
GLIB_AVAILABLE_IN_2_58
gboolean g_spawn_async_with_fds (const gchar *working_directory,
diff --git a/glib/tests/spawn-singlethread.c b/glib/tests/spawn-singlethread.c
index cfc8fd491..9a18c0640 100644
--- a/glib/tests/spawn-singlethread.c
+++ b/glib/tests/spawn-singlethread.c
@@ -30,6 +30,10 @@
#ifdef G_OS_UNIX
#include <glib-unix.h>
+#include <glib/gstdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
#endif
#ifdef G_OS_WIN32
@@ -421,6 +425,72 @@ test_spawn_nonexistent (void)
g_clear_error (&error);
}
+/* Test that FD assignments in a spawned process don’t overwrite and break the
+ * child_err_report_fd which is used to report error information back from the
+ * intermediate child process to the parent.
+ *
+ * https://gitlab.gnome.org/GNOME/glib/-/issues/2097 */
+static void
+test_spawn_fd_assignment_clash (void)
+{
+#ifdef G_OS_UNIX
+ int tmp_fd;
+ guint i;
+ const guint n_fds = 10;
+ gint source_fds[n_fds];
+ gint target_fds[n_fds];
+ const gchar *argv[] = { "/nonexistent" };
+ gboolean retval;
+ GError *local_error = NULL;
+ struct stat statbuf;
+
+ /* Open a temporary file and duplicate its FD several times so we have several
+ * FDs to remap in the child process. */
+ tmp_fd = g_file_open_tmp ("glib-spawn-test-XXXXXX", NULL, NULL);
+ g_assert_cmpint (tmp_fd, >=, 0);
+
+ for (i = 0; i < (n_fds - 1); ++i)
+ {
+ int source = fcntl (tmp_fd, F_DUPFD_CLOEXEC, 3);
+ g_assert_cmpint (source, >=, 0);
+ source_fds[i] = source;
+ target_fds[i] = source + n_fds;
+ }
+
+ source_fds[i] = tmp_fd;
+ target_fds[i] = tmp_fd + n_fds;
+
+ /* Print out the FD map. */
+ g_test_message ("FD map:");
+ for (i = 0; i < n_fds; i++)
+ g_test_message (" • %d → %d", source_fds[i], target_fds[i]);
+
+ /* Spawn the subprocess. This should fail because the executable doesn’t
+ * exist. */
+ retval = g_spawn_async_with_pipes_and_fds (NULL, argv, NULL, G_SPAWN_DEFAULT,
+ NULL, NULL, -1, -1, -1,
+ source_fds, target_fds, n_fds,
+ NULL, NULL, NULL, NULL,
+ &local_error);
+ g_assert_error (local_error, G_SPAWN_ERROR, G_SPAWN_ERROR_NOENT);
+ g_assert_false (retval);
+
+ g_clear_error (&local_error);
+
+ /* Check nothing was written to the temporary file, as would happen if the FD
+ * mapping was messed up to conflict with the child process error reporting FD.
+ * See https://gitlab.gnome.org/GNOME/glib/-/issues/2097 */
+ g_assert_no_errno (fstat (tmp_fd, &statbuf));
+ g_assert_cmpuint (statbuf.st_size, ==, 0);
+
+ /* Clean up. */
+ for (i = 0; i < n_fds; i++)
+ g_close (source_fds[i], NULL);
+#else /* !G_OS_UNIX */
+ g_test_skip ("FD redirection only supported on Unix");
+#endif /* !G_OS_UNIX */
+}
+
int
main (int argc,
char *argv[])
@@ -456,6 +526,7 @@ main (int argc,
g_test_add_func ("/gthread/spawn-script", test_spawn_script);
g_test_add_func ("/gthread/spawn/nonexistent", test_spawn_nonexistent);
g_test_add_func ("/gthread/spawn-posix-spawn", test_posix_spawn);
+ g_test_add_func ("/gthread/spawn/fd-assignment-clash", test_spawn_fd_assignment_clash);
ret = g_test_run();
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