Package: guile;
Reported by: Josselin Poiret <dev <at> jpoiret.xyz>
Date: Mon, 27 Dec 2021 21:27:01 UTC
Severity: normal
Tags: patch
Done: Ludovic Courtès <ludo <at> gnu.org>
Bug is archived. No further changes may be made.
View this message in rfc822 format
From: Josselin Poiret <dev <at> jpoiret.xyz> To: Josselin Poiret <dev <at> jpoiret.xyz>, Ludovic Courtès <ludo <at> gnu.org> Cc: 52835 <at> debbugs.gnu.org Subject: bug#52835: [PATCH v8 1/2] Add spawn. Date: Sat, 7 Jan 2023 17:07:46 +0100
* libguile/posix.c: Include spawn.h from Gnulib.
(do_spawn, scm_spawn_process): New functions.
---
doc/ref/posix.texi | 34 ++++++++--
libguile/posix.c | 162 ++++++++++++++++++++++++++++++++++++++++++++-
libguile/posix.h | 1 +
3 files changed, 192 insertions(+), 5 deletions(-)
diff --git a/doc/ref/posix.texi b/doc/ref/posix.texi
index bde0f150c..36e1f5040 100644
--- a/doc/ref/posix.texi
+++ b/doc/ref/posix.texi
@@ -2045,15 +2045,41 @@ safe to call after a multithreaded fork, which is a very limited set.
Guile issues a warning if it detects a fork from a multi-threaded
program.
-If you are going to @code{exec} soon after forking, the procedures in
-@code{(ice-9 popen)} may be useful to you, as they fork and exec within
-an async-signal-safe function carefully written to ensure robust program
-behavior, even in the presence of threads. @xref{Pipes}, for more.
+@quotation Note
+If you are only looking to fork+exec with some pipes set up, using pipes
+or the more primitive @code{spawn} will be more robust (e.g. in the
+presence of threads), and is more portable. @xref{Pipes} for more.
+@end quotation
This procedure has been renamed from @code{fork} to avoid a naming conflict
with the scsh fork.
@end deffn
+@deffn {Scheme Procedure} spawn program [#:args=(list program)] @
+ [#:env=(environ)] [#:in=(fileno (current-input-port))] @
+ [#:out=(fileno (current-output-port))] @
+ [#:err=(fileno (current-error-port))] @
+ [#:use-path?=#t]
+
+Spawns a new child process executing @var{program} with argument list
+@var{args} (which must include the name of the executable as a first
+element), with its environment variables set to @var{env} and standard
+input/output/error file descriptors to @var{in}, @var{out}, @var{err},
+after closing all other file descriptors. When @var{use-path?} is
+false, @var{program} should be a path to an executable file, but when
+@var{use-path?} is true, the environment variable @code{PATH} is
+searched to find the corresponding executable.
+
+Failure to exec in the child may be caught early and reported as an
+exception, or the child may also exit with return code 127, depending on
+how spawn is implemented for the specific system. You therefore must be
+able to handle both cases.
+
+The return value is the pid of the spawned child process.
+
+This procedure is portable and should be thread-safe.
+@end deffn
+
@deffn {Scheme Procedure} nice incr
@deffnx {C Function} scm_nice (incr)
@cindex process priority
diff --git a/libguile/posix.c b/libguile/posix.c
index b5352c2c4..f79875075 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -33,6 +33,7 @@
#include <sys/types.h>
#include <uniconv.h>
#include <unistd.h>
+#include <spawn.h>
#ifdef HAVE_SCHED_H
# include <sched.h>
@@ -63,6 +64,7 @@
#include "fports.h"
#include "gettext.h"
#include "gsubr.h"
+#include "keywords.h"
#include "list.h"
#include "modules.h"
#include "numbers.h"
@@ -1426,6 +1428,158 @@ start_child (const char *exec_file, char **exec_argv,
}
#endif
+static pid_t
+do_spawn (char *exec_file, char **exec_argv, char **exec_env,
+ int in, int out, int err, int spawnp)
+{
+ pid_t pid = -1;
+
+ posix_spawn_file_actions_t actions;
+ posix_spawnattr_t *attrp = NULL;
+
+ int max_fd = 1024;
+
+#if defined (HAVE_GETRLIMIT) && defined (RLIMIT_NOFILE)
+ {
+ struct rlimit lim = { 0, 0 };
+ if (getrlimit (RLIMIT_NOFILE, &lim) == 0)
+ max_fd = lim.rlim_cur;
+ }
+#endif
+
+ posix_spawn_file_actions_init (&actions);
+
+ int free_fd_slots = 0;
+ int fd_slot[3];
+
+ for (int fdnum = 3;free_fd_slots < 3 && fdnum < max_fd;fdnum++)
+ {
+ if (fdnum != in && fdnum != out && fdnum != err)
+ {
+ fd_slot[free_fd_slots] = fdnum;
+ free_fd_slots++;
+ }
+ }
+
+ /* Move the fds out of the way, so that duplicate fds or fds equal
+ to 0, 1, 2 don't trample each other */
+
+ posix_spawn_file_actions_adddup2 (&actions, in, fd_slot[0]);
+ posix_spawn_file_actions_adddup2 (&actions, out, fd_slot[1]);
+ posix_spawn_file_actions_adddup2 (&actions, err, fd_slot[2]);
+ posix_spawn_file_actions_adddup2 (&actions, fd_slot[0], 0);
+ posix_spawn_file_actions_adddup2 (&actions, fd_slot[1], 1);
+ posix_spawn_file_actions_adddup2 (&actions, fd_slot[2], 2);
+
+ while (--max_fd > 2)
+ posix_spawn_file_actions_addclose (&actions, max_fd);
+
+ int res = -1;
+ if (spawnp)
+ res = posix_spawnp (&pid, exec_file, &actions, attrp,
+ exec_argv, exec_env);
+ else
+ res = posix_spawn (&pid, exec_file, &actions, attrp,
+ exec_argv, exec_env);
+ if (res != 0)
+ return -1;
+
+ return pid;
+}
+
+SCM k_args, k_env, k_in, k_out, k_err, k_use_path;
+
+SCM_DEFINE (scm_spawn_process, "spawn", 1, 0, 1,
+ (SCM program, SCM keyword_args),
+ "Spawns a new child process executing @var{program} with no arguments.\n\n"
+ "If the boolean keyword argument @code{#:use-path?} is provided, it\n"
+ "selects whether the @code{PATH} environment variable should be\n"
+ "inspected to find @var{program}. It is true by default.\n\n"
+ "If the keyword arguments @code{#:args}, @code{#:env}, are provided,\n"
+ "they respectively modify the arguments or the environment of the\n"
+ "spawning program.\n\n"
+ "If the keyword arguments @code{#:in}, @code{#:out} or @code{#:err}\n"
+ "are provided, they respectively modify the default input, output\n"
+ "and error file descriptor of the spawning program to these values.")
+#define FUNC_NAME s_scm_spawn_process
+{
+ SCM args, env, in_scm, out_scm, err_scm, use_path;
+ args = SCM_UNDEFINED;
+ env = SCM_UNDEFINED;
+ in_scm = SCM_UNDEFINED;
+ out_scm = SCM_UNDEFINED;
+ err_scm = SCM_UNDEFINED;
+ use_path = SCM_BOOL_T;
+
+ scm_c_bind_keyword_arguments (FUNC_NAME, keyword_args, 0,
+ k_args, &args,
+ k_env, &env,
+ k_in, &in_scm,
+ k_out, &out_scm,
+ k_err, &err_scm,
+ k_use_path, &use_path,
+ SCM_UNDEFINED);
+
+ int pid = -1;
+ char *exec_file;
+ char **exec_argv;
+ char **exec_env;
+ int in, out, err;
+
+ exec_file = scm_to_locale_string (program);
+
+ if (SCM_UNBNDP (args))
+ {
+ /* We use scm_gc_malloc here because that's the same as what
+ scm_i_allocate_string_pointers would do. */
+ exec_argv = scm_gc_malloc (2 * sizeof (char *),
+ "string pointers");
+ exec_argv[0] = exec_file;
+ exec_argv[1] = NULL;
+ }
+ else
+ {
+ exec_argv = scm_i_allocate_string_pointers (args);
+ if (exec_argv[0] == NULL)
+ {
+ free (exec_file);
+ scm_misc_error (FUNC_NAME, "Argument list must not be empty.",
+ SCM_EOL);
+ }
+ }
+
+ if (SCM_UNBNDP (env))
+ exec_env = environ;
+ else
+ exec_env = scm_i_allocate_string_pointers (env);
+
+ if (SCM_UNBNDP (in_scm))
+ in = SCM_FPORT_FDES (scm_current_input_port ());
+ else
+ in = scm_to_int (in_scm);
+
+ if (SCM_UNBNDP (out_scm))
+ out = SCM_FPORT_FDES (scm_current_output_port ());
+ else
+ out = scm_to_int (out_scm);
+
+ if (SCM_UNBNDP (err_scm))
+ err = SCM_FPORT_FDES (scm_current_error_port ());
+ else
+ err = scm_to_int (err_scm);
+
+ pid = do_spawn (exec_file, exec_argv, exec_env,
+ in, out, err, scm_to_bool (use_path));
+
+ free (exec_file);
+
+ if (pid == -1)
+ SCM_SYSERROR;
+
+ return scm_from_int (pid);
+}
+#undef FUNC_NAME
+
#ifdef HAVE_START_CHILD
static SCM
scm_piped_process (SCM prog, SCM args, SCM from, SCM to)
@@ -2547,5 +2701,11 @@ scm_init_posix ()
"scm_init_popen",
(scm_t_extension_init_func) scm_init_popen,
NULL);
-#endif /* HAVE_START_CHILD */
+#endif /* HAVE_FORK */
+ k_args = scm_from_utf8_keyword ("args");
+ k_env = scm_from_utf8_keyword ("env");
+ k_in = scm_from_utf8_keyword ("in");
+ k_out = scm_from_utf8_keyword ("out");
+ k_err = scm_from_utf8_keyword ("err");
+ k_use_path = scm_from_utf8_keyword ("use-path?");
}
diff --git a/libguile/posix.h b/libguile/posix.h
index 6504eaea8..5eeafd4cb 100644
--- a/libguile/posix.h
+++ b/libguile/posix.h
@@ -69,6 +69,7 @@ SCM_API SCM scm_tmpnam (void);
SCM_API SCM scm_tmpfile (void);
SCM_API SCM scm_open_pipe (SCM pipestr, SCM modes);
SCM_API SCM scm_close_pipe (SCM port);
+SCM_API SCM scm_spawn_process (SCM prog, SCM keyword_args);
SCM_API SCM scm_system_star (SCM cmds);
SCM_API SCM scm_utime (SCM object, SCM actime, SCM modtime,
SCM actimens, SCM modtimens, SCM flags);
base-commit: 4711d45176e9b75cef43699ed514669276af62fe
--
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