From 2fe108953ef6927a3e9835b5877096d9fd907f51 Mon Sep 17 00:00:00 2001
From: Pablo Galindo Salgado <pablogsal@gmail.com>
Date: Thu, 13 Sep 2018 11:15:02 -0700
Subject: [PATCH 1/6] Add support for POSIX_SPAWN_USEVFORK in posix_spawn when
 available

---
 Lib/test/test_posix.py                        | 13 ++++++++++++
 .../2018-09-13-11-14-38.bpo-34663.BtJz-5.rst  |  2 ++
 Modules/clinic/posixmodule.c.h                | 19 ++++++++++--------
 Modules/posixmodule.c                         | 20 +++++++++++++++----
 4 files changed, 42 insertions(+), 12 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index d402d4fb088ca2..808281d0f750a6 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1790,6 +1790,19 @@ def test_dup2(self):
         with open(dupfile) as f:
             self.assertEqual(f.read(), 'hello')
 
+    def test_usevfork(self):
+        try:
+            pid = posix.posix_spawn(
+                sys.executable,
+                [sys.executable, '-c', 'pass'],
+                os.environ,
+                usevfork=True
+            )
+        except NotImplementedError:
+            unittest.SkipTest("POSIX_SPAWN_USEVFORK not available on this system")
+        else:
+            self.assertEqual(os.waitpid(pid, 0), (pid, 0))
+
 
 def test_main():
     try:
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst b/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst
new file mode 100644
index 00000000000000..48dd639d27166c
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst	
@@ -0,0 +1,2 @@
+Added support for `usevfork` parameters of `posix_spawn`, which allows to
+use ``POSIX_SPAWN_USEVFORK`` when the flag is available in the system.
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index c3849a93c0c240..ca371c0fc0d917 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -1732,7 +1732,7 @@ os_execve(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *k
 PyDoc_STRVAR(os_posix_spawn__doc__,
 "posix_spawn($module, path, argv, env, /, *, file_actions=(),\n"
 "            setpgroup=None, resetids=False, setsigmask=(),\n"
-"            setsigdef=(), scheduler=None)\n"
+"            setsigdef=(), scheduler=None, usevfork=False)\n"
 "--\n"
 "\n"
 "Execute the program specified by path in a new process.\n"
@@ -1754,7 +1754,9 @@ PyDoc_STRVAR(os_posix_spawn__doc__,
 "  setsigdef\n"
 "    The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.\n"
 "  scheduler\n"
-"    A tuple with the scheduler policy (optional) and parameters.");
+"    A tuple with the scheduler policy (optional) and parameters.\n"
+"  usevfork\n"
+"    If the value is `True` the POSIX_SPAWN_USEVFORK will be activated.");
 
 #define OS_POSIX_SPAWN_METHODDEF    \
     {"posix_spawn", (PyCFunction)os_posix_spawn, METH_FASTCALL|METH_KEYWORDS, os_posix_spawn__doc__},
@@ -1763,14 +1765,14 @@ static PyObject *
 os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
                     PyObject *env, PyObject *file_actions,
                     PyObject *setpgroup, int resetids, PyObject *setsigmask,
-                    PyObject *setsigdef, PyObject *scheduler);
+                    PyObject *setsigdef, PyObject *scheduler, int usevfork);
 
 static PyObject *
 os_posix_spawn(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
-    static const char * const _keywords[] = {"", "", "", "file_actions", "setpgroup", "resetids", "setsigmask", "setsigdef", "scheduler", NULL};
-    static _PyArg_Parser _parser = {"O&OO|$OOiOOO:posix_spawn", _keywords, 0};
+    static const char * const _keywords[] = {"", "", "", "file_actions", "setpgroup", "resetids", "setsigmask", "setsigdef", "scheduler", "usevfork", NULL};
+    static _PyArg_Parser _parser = {"O&OO|$OOiOOOi:posix_spawn", _keywords, 0};
     path_t path = PATH_T_INITIALIZE("posix_spawn", "path", 0, 0);
     PyObject *argv;
     PyObject *env;
@@ -1780,12 +1782,13 @@ os_posix_spawn(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObje
     PyObject *setsigmask = NULL;
     PyObject *setsigdef = NULL;
     PyObject *scheduler = NULL;
+    int usevfork = 0;
 
     if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
-        path_converter, &path, &argv, &env, &file_actions, &setpgroup, &resetids, &setsigmask, &setsigdef, &scheduler)) {
+        path_converter, &path, &argv, &env, &file_actions, &setpgroup, &resetids, &setsigmask, &setsigdef, &scheduler, &usevfork)) {
         goto exit;
     }
-    return_value = os_posix_spawn_impl(module, &path, argv, env, file_actions, setpgroup, resetids, setsigmask, setsigdef, scheduler);
+    return_value = os_posix_spawn_impl(module, &path, argv, env, file_actions, setpgroup, resetids, setsigmask, setsigdef, scheduler, usevfork);
 
 exit:
     /* Cleanup for path */
@@ -6648,4 +6651,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=758ee0434fb03d90 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=adeb97aed906eb1b input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 7c02351a466130..7cddcea149eda4 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5188,7 +5188,7 @@ 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,
+                        PyObject *setsigdef, PyObject *scheduler, int usevfork,
                         posix_spawnattr_t *attrp)
 {
     long all_flags = 0;
@@ -5278,6 +5278,16 @@ parse_posix_spawn_flags(PyObject *setpgroup, int resetids, PyObject *setsigmask,
 #endif
     }
 
+    if (usevfork) {
+#ifdef POSIX_SPAWN_USEVFORK
+        all_flags |= POSIX_SPAWN_SETSCHEDULER;
+#else
+        PyErr_SetString(PyExc_NotImplementedError,
+                "The UseVFork option is not supported in this system.");
+        goto fail;
+#endif
+    }
+
     errno = posix_spawnattr_setflags(attrp, all_flags);
     if (errno) {
         posix_error();
@@ -5425,6 +5435,8 @@ os.posix_spawn
         The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.
     scheduler: object = NULL
         A tuple with the scheduler policy (optional) and parameters.
+    usevfork: bool(accept={int}) = False
+        If the value is `True` the POSIX_SPAWN_USEVFORK will be activated.
 
 Execute the program specified by path in a new process.
 [clinic start generated code]*/
@@ -5433,8 +5445,8 @@ static PyObject *
 os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
                     PyObject *env, PyObject *file_actions,
                     PyObject *setpgroup, int resetids, PyObject *setsigmask,
-                    PyObject *setsigdef, PyObject *scheduler)
-/*[clinic end generated code: output=45dfa4c515d09f2c input=2891c2f1d457e39b]*/
+                    PyObject *setsigdef, PyObject *scheduler, int usevfork)
+/*[clinic end generated code: output=7e7b403caa228664 input=1fc98a9706886420]*/
 {
     EXECV_CHAR **argvlist = NULL;
     EXECV_CHAR **envlist = NULL;
@@ -5504,7 +5516,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
     }
 
     if (parse_posix_spawn_flags(setpgroup, resetids, setsigmask,
-                                setsigdef, scheduler, &attr)) {
+                                setsigdef, scheduler, usevfork, &attr)) {
         goto exit;
     }
     attrp = &attr;

From e72c246d9c06d509f2e9e8a586780126f335f4a5 Mon Sep 17 00:00:00 2001
From: Pablo Galindo Salgado <pablogsal@gmail.com>
Date: Thu, 13 Sep 2018 12:18:06 -0700
Subject: [PATCH 2/6] Rename parameter to  and correct error

---
 Lib/test/test_posix.py         |  4 ++--
 Modules/clinic/posixmodule.c.h | 16 ++++++++--------
 Modules/posixmodule.c          | 14 +++++++-------
 3 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 808281d0f750a6..08cfa85e4c1ca2 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1790,13 +1790,13 @@ def test_dup2(self):
         with open(dupfile) as f:
             self.assertEqual(f.read(), 'hello')
 
-    def test_usevfork(self):
+    def test_vfork(self):
         try:
             pid = posix.posix_spawn(
                 sys.executable,
                 [sys.executable, '-c', 'pass'],
                 os.environ,
-                usevfork=True
+                use_vfork=True
             )
         except NotImplementedError:
             unittest.SkipTest("POSIX_SPAWN_USEVFORK not available on this system")
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index ca371c0fc0d917..f0af09269ed52a 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -1732,7 +1732,7 @@ os_execve(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *k
 PyDoc_STRVAR(os_posix_spawn__doc__,
 "posix_spawn($module, path, argv, env, /, *, file_actions=(),\n"
 "            setpgroup=None, resetids=False, setsigmask=(),\n"
-"            setsigdef=(), scheduler=None, usevfork=False)\n"
+"            setsigdef=(), scheduler=None, use_vfork=False)\n"
 "--\n"
 "\n"
 "Execute the program specified by path in a new process.\n"
@@ -1755,7 +1755,7 @@ PyDoc_STRVAR(os_posix_spawn__doc__,
 "    The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.\n"
 "  scheduler\n"
 "    A tuple with the scheduler policy (optional) and parameters.\n"
-"  usevfork\n"
+"  use_vfork\n"
 "    If the value is `True` the POSIX_SPAWN_USEVFORK will be activated.");
 
 #define OS_POSIX_SPAWN_METHODDEF    \
@@ -1765,13 +1765,13 @@ static PyObject *
 os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
                     PyObject *env, PyObject *file_actions,
                     PyObject *setpgroup, int resetids, PyObject *setsigmask,
-                    PyObject *setsigdef, PyObject *scheduler, int usevfork);
+                    PyObject *setsigdef, PyObject *scheduler, int use_vfork);
 
 static PyObject *
 os_posix_spawn(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
-    static const char * const _keywords[] = {"", "", "", "file_actions", "setpgroup", "resetids", "setsigmask", "setsigdef", "scheduler", "usevfork", NULL};
+    static const char * const _keywords[] = {"", "", "", "file_actions", "setpgroup", "resetids", "setsigmask", "setsigdef", "scheduler", "use_vfork", NULL};
     static _PyArg_Parser _parser = {"O&OO|$OOiOOOi:posix_spawn", _keywords, 0};
     path_t path = PATH_T_INITIALIZE("posix_spawn", "path", 0, 0);
     PyObject *argv;
@@ -1782,13 +1782,13 @@ os_posix_spawn(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObje
     PyObject *setsigmask = NULL;
     PyObject *setsigdef = NULL;
     PyObject *scheduler = NULL;
-    int usevfork = 0;
+    int use_vfork = 0;
 
     if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
-        path_converter, &path, &argv, &env, &file_actions, &setpgroup, &resetids, &setsigmask, &setsigdef, &scheduler, &usevfork)) {
+        path_converter, &path, &argv, &env, &file_actions, &setpgroup, &resetids, &setsigmask, &setsigdef, &scheduler, &use_vfork)) {
         goto exit;
     }
-    return_value = os_posix_spawn_impl(module, &path, argv, env, file_actions, setpgroup, resetids, setsigmask, setsigdef, scheduler, usevfork);
+    return_value = os_posix_spawn_impl(module, &path, argv, env, file_actions, setpgroup, resetids, setsigmask, setsigdef, scheduler, use_vfork);
 
 exit:
     /* Cleanup for path */
@@ -6651,4 +6651,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=adeb97aed906eb1b input=a9049054013a1b77]*/
+/*[clinic end generated code: output=74cf88c3208b5088 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 7cddcea149eda4..8b555585a5f786 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5188,7 +5188,7 @@ 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, int usevfork,
+                        PyObject *setsigdef, PyObject *scheduler, int use_vfork,
                         posix_spawnattr_t *attrp)
 {
     long all_flags = 0;
@@ -5278,12 +5278,12 @@ parse_posix_spawn_flags(PyObject *setpgroup, int resetids, PyObject *setsigmask,
 #endif
     }
 
-    if (usevfork) {
+    if (use_vfork) {
 #ifdef POSIX_SPAWN_USEVFORK
         all_flags |= POSIX_SPAWN_SETSCHEDULER;
 #else
         PyErr_SetString(PyExc_NotImplementedError,
-                "The UseVFork option is not supported in this system.");
+                "The use_vfork option is not supported in this system.");
         goto fail;
 #endif
     }
@@ -5435,7 +5435,7 @@ os.posix_spawn
         The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.
     scheduler: object = NULL
         A tuple with the scheduler policy (optional) and parameters.
-    usevfork: bool(accept={int}) = False
+    use_vfork: bool(accept={int}) = False
         If the value is `True` the POSIX_SPAWN_USEVFORK will be activated.
 
 Execute the program specified by path in a new process.
@@ -5445,8 +5445,8 @@ static PyObject *
 os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
                     PyObject *env, PyObject *file_actions,
                     PyObject *setpgroup, int resetids, PyObject *setsigmask,
-                    PyObject *setsigdef, PyObject *scheduler, int usevfork)
-/*[clinic end generated code: output=7e7b403caa228664 input=1fc98a9706886420]*/
+                    PyObject *setsigdef, PyObject *scheduler, int use_vfork)
+/*[clinic end generated code: output=ed9323af139a50f7 input=d033288962226596]*/
 {
     EXECV_CHAR **argvlist = NULL;
     EXECV_CHAR **envlist = NULL;
@@ -5516,7 +5516,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
     }
 
     if (parse_posix_spawn_flags(setpgroup, resetids, setsigmask,
-                                setsigdef, scheduler, usevfork, &attr)) {
+                                setsigdef, scheduler, use_vfork, &attr)) {
         goto exit;
     }
     attrp = &attr;

From 2fe9bf1b5ac19b6f91ea0bcfb75dff5085970a0c Mon Sep 17 00:00:00 2001
From: Pablo Galindo Salgado <pablogsal@gmail.com>
Date: Thu, 13 Sep 2018 13:55:54 -0700
Subject: [PATCH 3/6] Add docs and improve implementation and naming

---
 Doc/library/os.rst             | 6 +++++-
 Lib/test/test_posix.py         | 5 +++--
 Modules/clinic/posixmodule.c.h | 4 ++--
 Modules/posixmodule.c          | 7 +++----
 4 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index bc8d5a8abbf31a..94677d48ab2e3f 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -3396,7 +3396,7 @@ written in Python, such as a mail server's external command delivery program.
 
 .. function:: posix_spawn(path, argv, env, *, file_actions=None, \
                           setpgroup=None, resetids=False, setsigmask=(), \
-                          setsigdef=(), scheduler=None)
+                          setsigdef=(), scheduler=None, use_vfork=False)
 
    Wraps the :c:func:`posix_spawn` C library API for use from Python.
 
@@ -3465,6 +3465,10 @@ written in Python, such as a mail server's external command delivery program.
    :c:data:`POSIX_SPAWN_SETSCHEDPARAM` and :c:data:`POSIX_SPAWN_SETSCHEDULER`
    flags.
 
+  If the value of *use_vfork* is true, the child will be created using
+  :c:func:`vfork` instead of :c:func:`fork`. This corresponds to the
+  GNU specific flag :c:data:`POSIX_SPAWN_USEVFORK`.
+
    .. versionadded:: 3.7
 
 
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 08cfa85e4c1ca2..e5048d5fc4d298 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1791,10 +1791,11 @@ def test_dup2(self):
             self.assertEqual(f.read(), 'hello')
 
     def test_vfork(self):
+        args = self.python_args()
         try:
             pid = posix.posix_spawn(
-                sys.executable,
-                [sys.executable, '-c', 'pass'],
+                args[0],
+                args,
                 os.environ,
                 use_vfork=True
             )
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index f0af09269ed52a..e35ef159632a51 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -1756,7 +1756,7 @@ PyDoc_STRVAR(os_posix_spawn__doc__,
 "  scheduler\n"
 "    A tuple with the scheduler policy (optional) and parameters.\n"
 "  use_vfork\n"
-"    If the value is `True` the POSIX_SPAWN_USEVFORK will be activated.");
+"    If the value is true the POSIX_SPAWN_USEVFORK will be activated.");
 
 #define OS_POSIX_SPAWN_METHODDEF    \
     {"posix_spawn", (PyCFunction)os_posix_spawn, METH_FASTCALL|METH_KEYWORDS, os_posix_spawn__doc__},
@@ -6651,4 +6651,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=74cf88c3208b5088 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=d4d3d9754ff072e7 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 8b555585a5f786..8820f516bced13 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5282,8 +5282,7 @@ parse_posix_spawn_flags(PyObject *setpgroup, int resetids, PyObject *setsigmask,
 #ifdef POSIX_SPAWN_USEVFORK
         all_flags |= POSIX_SPAWN_SETSCHEDULER;
 #else
-        PyErr_SetString(PyExc_NotImplementedError,
-                "The use_vfork option is not supported in this system.");
+        argument_unavailable_error("posix_spawn", "use_vfork");
         goto fail;
 #endif
     }
@@ -5436,7 +5435,7 @@ os.posix_spawn
     scheduler: object = NULL
         A tuple with the scheduler policy (optional) and parameters.
     use_vfork: bool(accept={int}) = False
-        If the value is `True` the POSIX_SPAWN_USEVFORK will be activated.
+        If the value is true the POSIX_SPAWN_USEVFORK will be activated.
 
 Execute the program specified by path in a new process.
 [clinic start generated code]*/
@@ -5446,7 +5445,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
                     PyObject *env, PyObject *file_actions,
                     PyObject *setpgroup, int resetids, PyObject *setsigmask,
                     PyObject *setsigdef, PyObject *scheduler, int use_vfork)
-/*[clinic end generated code: output=ed9323af139a50f7 input=d033288962226596]*/
+/*[clinic end generated code: output=ed9323af139a50f7 input=9ca9c905ec19bf04]*/
 {
     EXECV_CHAR **argvlist = NULL;
     EXECV_CHAR **envlist = NULL;

From 70db5e975cbebbd783d01bd56bfc3ec01d6de786 Mon Sep 17 00:00:00 2001
From: Pablo Galindo Salgado <pablogsal@gmail.com>
Date: Thu, 13 Sep 2018 14:32:39 -0700
Subject: [PATCH 4/6] Improve documentation and error messages

---
 Doc/library/os.rst                                          | 5 ++++-
 Lib/test/test_posix.py                                      | 6 +++---
 .../2018-09-13-11-14-38.bpo-34663.BtJz-5.rst                | 5 +++--
 Modules/posixmodule.c                                       | 3 ++-
 4 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 94677d48ab2e3f..d94e10fca0099c 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -3467,7 +3467,10 @@ written in Python, such as a mail server's external command delivery program.
 
   If the value of *use_vfork* is true, the child will be created using
   :c:func:`vfork` instead of :c:func:`fork`. This corresponds to the
-  GNU specific flag :c:data:`POSIX_SPAWN_USEVFORK`.
+  GNU specific flag :c:data:`POSIX_SPAWN_USEVFORK`. If the flag is not
+  available on the platform, :exc:`NotImplementedError` will be raised.
+
+   Availability: Using *use_vfork* is only available on Linux.
 
    .. versionadded:: 3.7
 
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index e5048d5fc4d298..4defcd74ff31c7 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1791,7 +1791,7 @@ def test_dup2(self):
             self.assertEqual(f.read(), 'hello')
 
     def test_vfork(self):
-        args = self.python_args()
+        args = self.python_args('-c', 'pass')
         try:
             pid = posix.posix_spawn(
                 args[0],
@@ -1799,8 +1799,8 @@ def test_vfork(self):
                 os.environ,
                 use_vfork=True
             )
-        except NotImplementedError:
-            unittest.SkipTest("POSIX_SPAWN_USEVFORK not available on this system")
+        except NotImplementedError as e:
+            raise unittest.SkipTest(e)
         else:
             self.assertEqual(os.waitpid(pid, 0), (pid, 0))
 
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst b/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst
index 48dd639d27166c..b6ba2b45c56327 100644
--- a/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst	
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst	
@@ -1,2 +1,3 @@
-Added support for `usevfork` parameters of `posix_spawn`, which allows to
-use ``POSIX_SPAWN_USEVFORK`` when the flag is available in the system.
+Added support for `use_vfork` parameters of :func:`os.posix_spawn`, which
+allows to use ``POSIX_SPAWN_USEVFORK`` when the flag is available in the
+system.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 8820f516bced13..587279cbe23937 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5282,7 +5282,8 @@ parse_posix_spawn_flags(PyObject *setpgroup, int resetids, PyObject *setsigmask,
 #ifdef POSIX_SPAWN_USEVFORK
         all_flags |= POSIX_SPAWN_SETSCHEDULER;
 #else
-        argument_unavailable_error("posix_spawn", "use_vfork");
+        PyErr_SetString(PyExc_NotImplementedError,
+                "The POSIX_SPAWN_USEVFORK flag is unavailable on this platform");
         goto fail;
 #endif
     }

From 6f03dc597bf4a9e8061741ce02037b65c7010952 Mon Sep 17 00:00:00 2001
From: Pablo Galindo Salgado <pablogsal@gmail.com>
Date: Fri, 14 Sep 2018 14:20:47 -0700
Subject: [PATCH 5/6] Add availability and clean tests

---
 Doc/library/os.rst     | 2 +-
 Lib/test/test_posix.py | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index d94e10fca0099c..7d552557e412ca 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -3470,7 +3470,7 @@ written in Python, such as a mail server's external command delivery program.
   GNU specific flag :c:data:`POSIX_SPAWN_USEVFORK`. If the flag is not
   available on the platform, :exc:`NotImplementedError` will be raised.
 
-   Availability: Using *use_vfork* is only available on Linux.
+   Availability: Unix. Using *use_vfork* is only available on Linux.
 
    .. versionadded:: 3.7
 
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 4defcd74ff31c7..bea2d5884594fe 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1799,8 +1799,8 @@ def test_vfork(self):
                 os.environ,
                 use_vfork=True
             )
-        except NotImplementedError as e:
-            raise unittest.SkipTest(e)
+        except NotImplementedError as exc:
+            raise self.skipTest(str(exc))
         else:
             self.assertEqual(os.waitpid(pid, 0), (pid, 0))
 

From c8b46c6d71665edbc5be012706804175dbe2dbd8 Mon Sep 17 00:00:00 2001
From: Pablo Galindo Salgado <pablogsal@gmail.com>
Date: Fri, 14 Sep 2018 14:39:46 -0700
Subject: [PATCH 6/6] fixup! Add availability and clean tests

---
 Doc/library/os.rst                            | 32 +++++++++----------
 Lib/test/test_posix.py                        |  2 +-
 .../2018-09-13-11-14-38.bpo-34663.BtJz-5.rst  |  6 ++--
 3 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 7d552557e412ca..46d42d394016c8 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -3435,22 +3435,22 @@ written in Python, such as a mail server's external command delivery program.
    :c:func:`posix_spawn_file_actions_adddup2` API calls used to prepare
    for the :c:func:`posix_spawn` call itself.
 
-   The *setpgroup* argument will set the process group of the child to the value
-   specified. If the value specified is 0, the child's process group ID will be
-   made the same as its process ID. If the value of *setpgroup* is not set, the
-   child will inherit the parent's process group ID. This argument corresponds
-   to the C library :c:data:`POSIX_SPAWN_SETPGROUP` flag.
+   The *setpgroup* argument will set the process group of the child process to
+   the value specified. If the value specified is 0, the child's process group
+   ID will be made the same as its process ID. If the value of *setpgroup* is
+   not set, the child process will inherit the parent's process group ID. This
+   argument corresponds to the C library :c:data:`POSIX_SPAWN_SETPGROUP` flag.
 
    If the *resetids* argument is ``True`` it will reset the effective UID and
-   GID of the child to the real UID and GID of the parent process. If the
-   argument is ``False``, then the child retains the effective UID and GID of
-   the parent. In either case, if the set-user-ID and set-group-ID permission
-   bits are enabled on the executable file, their effect will override the
-   setting of the effective UID and GID. This argument corresponds to the C
-   library :c:data:`POSIX_SPAWN_RESETIDS` flag.
+   GID of the child process to the real UID and GID of the parent process. If
+   the argument is ``False``, then the child process retains the effective UID
+   and GID of the parent. In either case, if the set-user-ID and set-group-ID
+   permission bits are enabled on the executable file, their effect will
+   override the setting of the effective UID and GID. This argument corresponds
+   to the C library :c:data:`POSIX_SPAWN_RESETIDS` flag.
 
    The *setsigmask* argument will set the signal mask to the signal set
-   specified. If the parameter is not used, then the child inherits the
+   specified. If the parameter is not used, then the child process inherits the
    parent's signal mask. This argument corresponds to the C library
    :c:data:`POSIX_SPAWN_SETSIGMASK` flag.
 
@@ -3465,10 +3465,10 @@ written in Python, such as a mail server's external command delivery program.
    :c:data:`POSIX_SPAWN_SETSCHEDPARAM` and :c:data:`POSIX_SPAWN_SETSCHEDULER`
    flags.
 
-  If the value of *use_vfork* is true, the child will be created using
-  :c:func:`vfork` instead of :c:func:`fork`. This corresponds to the
-  GNU specific flag :c:data:`POSIX_SPAWN_USEVFORK`. If the flag is not
-  available on the platform, :exc:`NotImplementedError` will be raised.
+  If the value of *use_vfork* is true, the child process will be created using
+  :c:func:`vfork` instead of :c:func:`fork`. This corresponds to the GNU
+  specific flag :c:data:`POSIX_SPAWN_USEVFORK`. If the flag is not available on
+  the platform, :exc:`NotImplementedError` will be raised.
 
    Availability: Unix. Using *use_vfork* is only available on Linux.
 
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index bea2d5884594fe..6e9c2b7667a13c 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1790,7 +1790,7 @@ def test_dup2(self):
         with open(dupfile) as f:
             self.assertEqual(f.read(), 'hello')
 
-    def test_vfork(self):
+    def test_use_vfork(self):
         args = self.python_args('-c', 'pass')
         try:
             pid = posix.posix_spawn(
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst b/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst
index b6ba2b45c56327..d5ccb0b881c208 100644
--- a/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst	
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-09-13-11-14-38.bpo-34663.BtJz-5.rst	
@@ -1,3 +1,3 @@
-Added support for `use_vfork` parameters of :func:`os.posix_spawn`, which
-allows to use ``POSIX_SPAWN_USEVFORK`` when the flag is available in the
-system.
+Added support for `use_vfork` parameter of :func:`os.posix_spawn`, which
+allows to use ``POSIX_SPAWN_USEVFORK`` constant when the flag is available
+in the system.