gh-113119 fix environment handling in subprocess.Popen when posix_spawn is used (#113120)

* Allow posix_spawn to inherit environment form parent environ variable.

With this change, posix_spawn call can behave similarly to execv with regards to environments when used in subprocess functions.

Doc/library/os.rst

@@ -4570,7 +4570,8 @@ written in Python, such as a mail server's external command delivery program.
    Most users should use :func:`subprocess.run` instead of :func:`posix_spawn`.
 
    The positional-only arguments *path*, *args*, and *env* are similar to
-   :func:`execve`.
+   :func:`execve`. *env* is allowed to be ``None``, in which case current
+   process' environment is used.
 
    The *path* parameter is the path to the executable file.  The *path* should
    contain a directory.  Use :func:`posix_spawnp` to pass an executable file
@@ -4645,6 +4646,9 @@ written in Python, such as a mail server's external command delivery program.
 
    .. versionadded:: 3.8
 
+   .. versionchanged:: 3.13
+      *env* parameter accepts ``None``.
+
    .. availability:: Unix, not Emscripten, not WASI.
 
 .. function:: posix_spawnp(path, argv, env, *, file_actions=None, \

Doc/whatsnew/3.13.rst

@@ -289,6 +289,10 @@ os
   ``False`` on Windows.
   (Contributed by Serhiy Storchaka in :gh:`59616`)
 
+* :func:`os.posix_spawn` now accepts ``env=None``, which makes the newly spawned
+  process use the current process environment.
+  (Contributed by Jakub Kulik in :gh:`113119`.)
+
 pathlib
 -------
 

Lib/subprocess.py

@@ -1756,9 +1756,6 @@ def _posix_spawn(self, args, executable, env, restore_signals,
                          c2pread, c2pwrite,
                          errread, errwrite):
             """Execute program using os.posix_spawn()."""
-            if env is None:
-                env = os.environ
-
             kwargs = {}
             if restore_signals:
                 # See _Py_RestoreSignals() in Python/pylifecycle.c

Misc/NEWS.d/next/Library/2023-12-15-18-13-59.gh-issue-113119.al-569.rst

@@ -0,0 +1,2 @@
+:func:`os.posix_spawn` now accepts ``env=None``, which makes the newly spawned
+process use the current process environment. Patch by Jakub Kulik.

Modules/posixmodule.c

@@ -7129,9 +7129,9 @@ py_posix_spawn(int use_posix_spawnp, PyObject *module, path_t *path, PyObject *a
         return NULL;
     }
 
-    if (!PyMapping_Check(env)) {
+    if (!PyMapping_Check(env) && env != Py_None) {
         PyErr_Format(PyExc_TypeError,
-                     "%s: environment must be a mapping object", func_name);
+                     "%s: environment must be a mapping object or None", func_name);
         goto exit;
     }
 
@@ -7145,10 +7145,14 @@ py_posix_spawn(int use_posix_spawnp, PyObject *module, path_t *path, PyObject *a
         goto exit;
     }
 
+    if (env == Py_None) {
+        envlist = environ;
+    } else {
         envlist = parse_envlist(env, &envc);
         if (envlist == NULL) {
             goto exit;
         }
+    }
 
     if (file_actions != NULL && file_actions != Py_None) {
         /* There is a bug in old versions of glibc that makes some of the
@@ -7210,7 +7214,7 @@ py_posix_spawn(int use_posix_spawnp, PyObject *module, path_t *path, PyObject *a
     if (attrp) {
         (void)posix_spawnattr_destroy(attrp);
     }
-    if (envlist) {
+    if (envlist && envlist != environ) {
         free_string_array(envlist, envc);
     }
     if (argvlist) {