commit 03c52f2f63a8abeb4afb75e9da46c7d6c0a8afd5
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Tue Aug 27 14:56:27 2019 -0700
committer GitHub <noreply@github.com> Tue Aug 27 14:56:27 2019 -0700
tree 1352ac655ca27a99ae3de2af28907b88bec7d630
parent caf7a30efecef21def997ab214dc6c1604d90a84

bpo-37951: Lift subprocess's fork() restriction (GH-15544)

(cherry picked from commit 98d90f745d35d5d07bffcb46788b50e05eea56c6)

Co-authored-by: Christian Heimes <christian@python.org>

Modules/_posixsubprocess.c

diff --git a/Modules/_posixsubprocess.c b/Modules/_posixsubprocess.c
index 81a23c6..e693e53 100644
--- a/Modules/_posixsubprocess.c
+++ b/Modules/_posixsubprocess.c
@@ -583,8 +583,10 @@
             &restore_signals, &call_setsid, &preexec_fn))
         return NULL;
 
-    if (_PyInterpreterState_Get() != PyInterpreterState_Main()) {
-        PyErr_SetString(PyExc_RuntimeError, "fork not supported for subinterpreters");
+    if ((preexec_fn != Py_None) &&
+            (_PyInterpreterState_Get() != PyInterpreterState_Main())) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "preexec_fn not supported within subinterpreters");
         return NULL;
     }