bpo-20104: Add flag capabilities to posix_spawn (GH-6693)

Implement the "attributes objects" parameter of `os.posix_spawn` to complete the implementation and fully cover the underlying API.

Modules/posixmodule.c

@@ -5177,6 +5177,114 @@ enum posix_spawn_file_actions_identifier {
     POSIX_SPAWN_DUP2
 };
 
+static int
+convert_sched_param(PyObject *param, struct sched_param *res);
+
+static int
+parse_posix_spawn_flags(PyObject *setpgroup, int resetids, PyObject *setsigmask,
+                        PyObject *setsigdef, PyObject *scheduler,
+                        posix_spawnattr_t *attrp)
+{
+    long all_flags = 0;
+
+    errno = posix_spawnattr_init(attrp);
+    if (errno) {
+        posix_error();
+        return -1;
+    }
+
+    if (setpgroup) {
+        pid_t pgid = PyLong_AsPid(setpgroup);
+        if (pgid == (pid_t)-1 && PyErr_Occurred()) {
+            goto fail;
+        }
+        errno = posix_spawnattr_setpgroup(attrp, pgid);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETPGROUP;
+    }
+
+    if (resetids) {
+        all_flags |= POSIX_SPAWN_RESETIDS;
+    }
+
+   if (setsigmask) {
+        sigset_t set;
+        if (!_Py_Sigset_Converter(setsigmask, &set)) {
+            goto fail;
+        }
+        errno = posix_spawnattr_setsigmask(attrp, &set);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETSIGMASK;
+    }
+
+    if (setsigdef) {
+        sigset_t set;
+        if (!_Py_Sigset_Converter(setsigdef, &set)) {
+            goto fail;
+        }
+        errno = posix_spawnattr_setsigdefault(attrp, &set);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETSIGDEF;
+    }
+
+    if (scheduler) {
+#ifdef POSIX_SPAWN_SETSCHEDULER
+        PyObject *py_schedpolicy;
+        struct sched_param schedparam;
+
+        if (!PyArg_ParseTuple(scheduler, "OO&"
+                        ";A scheduler tuple must have two elements",
+                        &py_schedpolicy, convert_sched_param, &schedparam)) {
+            goto fail;
+        }
+        if (py_schedpolicy != Py_None) {
+            int schedpolicy = _PyLong_AsInt(py_schedpolicy);
+
+            if (schedpolicy == -1 && PyErr_Occurred()) {
+                goto fail;
+            }
+            errno = posix_spawnattr_setschedpolicy(attrp, schedpolicy);
+            if (errno) {
+                posix_error();
+                goto fail;
+            }
+            all_flags |= POSIX_SPAWN_SETSCHEDULER;
+        }
+        errno = posix_spawnattr_setschedparam(attrp, &schedparam);
+        if (errno) {
+            posix_error();
+            goto fail;
+        }
+        all_flags |= POSIX_SPAWN_SETSCHEDPARAM;
+#else
+        PyErr_SetString(PyExc_NotImplementedError,
+                "The scheduler option is not supported in this system.");
+        goto fail;
+#endif
+    }
+
+    errno = posix_spawnattr_setflags(attrp, all_flags);
+    if (errno) {
+        posix_error();
+        goto fail;
+    }
+
+    return 0;
+
+fail:
+    (void)posix_spawnattr_destroy(attrp);
+    return -1;
+}
+
 static int
 parse_file_actions(PyObject *file_actions,
                    posix_spawn_file_actions_t *file_actionsp,
@@ -5277,6 +5385,7 @@ parse_file_actions(PyObject *file_actions,
         }
         Py_DECREF(file_action);
     }
+
     Py_DECREF(seq);
     return 0;
 
@@ -5299,19 +5408,33 @@ os.posix_spawn
     file_actions: object = None
         A sequence of file action tuples.
     /
-
+    *
+    setpgroup: object = NULL
+        The pgroup to use with the POSIX_SPAWN_SETPGROUP flag.
+    resetids: bool(accept={int}) = False
+        If the value is `True` the POSIX_SPAWN_RESETIDS will be activated.
+    setsigmask: object(c_default='NULL') = ()
+        The sigmask to use with the POSIX_SPAWN_SETSIGMASK flag.
+    setsigdef: object(c_default='NULL') = ()
+        The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.
+    scheduler: object = NULL
+        A tuple with the scheduler policy (optional) and parameters.
 Execute the program specified by path in a new process.
 [clinic start generated code]*/
 
 static PyObject *
 os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
-                    PyObject *env, PyObject *file_actions)
-/*[clinic end generated code: output=d023521f541c709c input=a3db1021d33230dc]*/
+                    PyObject *env, PyObject *file_actions,
+                    PyObject *setpgroup, int resetids, PyObject *setsigmask,
+                    PyObject *setsigdef, PyObject *scheduler)
+/*[clinic end generated code: output=45dfa4c515d09f2c input=2d7a7578430a90f0]*/
 {
     EXECV_CHAR **argvlist = NULL;
     EXECV_CHAR **envlist = NULL;
     posix_spawn_file_actions_t file_actions_buf;
     posix_spawn_file_actions_t *file_actionsp = NULL;
+    posix_spawnattr_t attr;
+    posix_spawnattr_t *attrp = NULL;
     Py_ssize_t argc, envc;
     PyObject *result = NULL;
     PyObject *temp_buffer = NULL;
@@ -5373,9 +5496,15 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
         file_actionsp = &file_actions_buf;
     }
 
+    if (parse_posix_spawn_flags(setpgroup, resetids, setsigmask,
+                                setsigdef, scheduler, &attr)) {
+        goto exit;
+    }
+    attrp = &attr;
+
     _Py_BEGIN_SUPPRESS_IPH
     err_code = posix_spawn(&pid, path->narrow,
-                           file_actionsp, NULL, argvlist, envlist);
+                           file_actionsp, attrp, argvlist, envlist);
     _Py_END_SUPPRESS_IPH
     if (err_code) {
         errno = err_code;
@@ -5388,6 +5517,9 @@ exit:
     if (file_actionsp) {
         (void)posix_spawn_file_actions_destroy(file_actionsp);
     }
+    if (attrp) {
+        (void)posix_spawnattr_destroy(attrp);
+    }
     if (envlist) {
         free_string_array(envlist, envc);
     }