bpo-35537: Change subprocess to use posix_spawnp instead of posix_spawn

Doc/whatsnew/3.8.rst

@@ -317,14 +317,13 @@ xml
 Optimizations
 =============
 
-* The :mod:`subprocess` module can now use the :func:`os.posix_spawn` function
+* The :mod:`subprocess` module can now use the :func:`os.posix_spawnp` function
   in some cases for better performance. Currently, it is only used on macOS
   and Linux (using glibc 2.24 or newer) if all these conditions are met:
 
   * *close_fds* is false;
   * *preexec_fn*, *pass_fds*, *cwd* and *start_new_session* parameters
-    are not set;
-  * the *executable* path contains a directory.
+    are not set.
 
 * :func:`shutil.copyfile`, :func:`shutil.copy`, :func:`shutil.copy2`,
   :func:`shutil.copytree` and :func:`shutil.move` use platform-specific

Lib/subprocess.py

@@ -607,10 +607,10 @@ def getoutput(cmd):
     return getstatusoutput(cmd)[1]
 
 
-def _use_posix_spawn():
-    """Check if posix_spawn() can be used for subprocess.
+def _use_posix_spawnp():
+    """Check if posix_spawnp() can be used for subprocess.
 
-    subprocess requires a posix_spawn() implementation that properly reports
+    subprocess requires a posix_spawnp() implementation that properly reports
     errors to the parent process, & sets errno on the following failures:
 
     * Process attribute actions failed.
@@ -620,12 +620,12 @@ def _use_posix_spawn():
     Prefer an implementation which can use vfork() in some cases for best
     performance.
     """
-    if _mswindows or not hasattr(os, 'posix_spawn'):
-        # os.posix_spawn() is not available
+    if _mswindows or not hasattr(os, 'posix_spawnp'):
+        # os.posix_spawnp() is not available
         return False
 
     if sys.platform == 'darwin':
-        # posix_spawn() is a syscall on macOS and properly reports errors
+        # posix_spawnp() is a syscall on macOS and properly reports errors
         return True
 
     # Check libc name and runtime libc version
@@ -640,8 +640,6 @@ def _use_posix_spawn():
         version = tuple(map(int, parts[1].split('.')))
 
         if sys.platform == 'linux' and libc == 'glibc' and version >= (2, 24):
-            # glibc 2.24 has a new Linux posix_spawn implementation using vfork
-            # which properly reports errors to the parent process.
             return True
         # Note: Don't use the implementation in earlier glibc because it doesn't
         # use vfork (even if glibc 2.26 added a pipe to properly report errors
@@ -650,11 +648,11 @@ def _use_posix_spawn():
         # os.confstr() or CS_GNU_LIBC_VERSION value not available
         pass
 
-    # By default, assume that posix_spawn() does not properly report errors.
+    # By default, assume that posix_spawnp() does not properly report errors.
     return False
 
 
-_USE_POSIX_SPAWN = _use_posix_spawn()
+_USE_POSIX_SPAWNP = _use_posix_spawnp()
 
 
 class Popen(object):
@@ -1461,11 +1459,11 @@ def _get_handles(self, stdin, stdout, stderr):
                     errread, errwrite)
 
 
-        def _posix_spawn(self, args, executable, env, restore_signals,
+        def _posix_spawnp(self, args, executable, env, restore_signals,
                          p2cread, p2cwrite,
                          c2pread, c2pwrite,
                          errread, errwrite):
-            """Execute program using os.posix_spawn()."""
+            """Execute program using os.posix_spawnp()."""
             if env is None:
                 env = os.environ
 
@@ -1493,7 +1491,7 @@ def _posix_spawn(self, args, executable, env, restore_signals,
             if file_actions:
                 kwargs['file_actions'] = file_actions
 
-            self.pid = os.posix_spawn(executable, args, env, **kwargs)
+            self.pid = os.posix_spawnp(executable, args, env, **kwargs)
             self._child_created = True
 
             self._close_pipe_fds(p2cread, p2cwrite,
@@ -1525,8 +1523,7 @@ def _execute_child(self, args, executable, preexec_fn, close_fds,
             if executable is None:
                 executable = args[0]
 
-            if (_USE_POSIX_SPAWN
-                    and os.path.dirname(executable)
+            if (_USE_POSIX_SPAWNP
                     and preexec_fn is None
                     and not close_fds
                     and not pass_fds
@@ -1535,10 +1532,8 @@ def _execute_child(self, args, executable, preexec_fn, close_fds,
                     and (c2pwrite == -1 or c2pwrite > 2)
                     and (errwrite == -1 or errwrite > 2)
                     and not start_new_session):
-                self._posix_spawn(args, executable, env, restore_signals,
-                                  p2cread, p2cwrite,
-                                  c2pread, c2pwrite,
-                                  errread, errwrite)
+                self._posix_spawnp(args, executable, env, restore_signals, p2cread,
+                                   p2cwrite, c2pread, c2pwrite, errread, errwrite)
                 return
 
             orig_executable = executable

Misc/NEWS.d/next/Library/2019-02-18-12-45-33.bpo-35537.xshtGJ.rst

@@ -0,0 +1 @@
+The :mod:`subprocess` now uses :func:`os.posix_spawnp` instead of :func:`os.posix_spawn`