Issue #7995: When calling accept() on a socket with a timeout, the returned

socket is now always non-blocking, regardless of the operating system.

Lib/socket.py

@@ -130,7 +130,13 @@ class socket(_socket.socket):
         For IP sockets, the address info is a pair (hostaddr, port).
         """
         fd, addr = self._accept()
-        return socket(self.family, self.type, self.proto, fileno=fd), addr
+        sock = socket(self.family, self.type, self.proto, fileno=fd)
+        # Issue #7995: if no default timeout is set and the listening
+        # socket had a (non-zero) timeout, force the new socket in blocking
+        # mode to override platform-specific socket flags inheritance.
+        if getdefaulttimeout() is None and self.gettimeout():
+            sock.setblocking(True)
+        return sock, addr
 
     def makefile(self, mode="r", buffering=None, *,
                  encoding=None, errors=None, newline=None):

Lib/test/test_socket.py

@@ -982,6 +982,23 @@ class NonBlockingTCPTests(ThreadedTCPSocketTest):
         def _testInitNonBlocking(self):
             pass
 
+    def testInheritFlags(self):
+        # Issue #7995: when calling accept() on a listening socket with a
+        # timeout, the resulting socket should not be non-blocking.
+        self.serv.settimeout(10)
+        try:
+            conn, addr = self.serv.accept()
+            message = conn.recv(len(MSG))
+        finally:
+            conn.close()
+            self.serv.settimeout(None)
+
+    def _testInheritFlags(self):
+        time.sleep(0.1)
+        self.cli.connect((HOST, self.port))
+        time.sleep(0.5)
+        self.cli.send(MSG)
+
     def testAccept(self):
         # Testing non-blocking accept
         self.serv.setblocking(0)

Misc/NEWS

@@ -30,6 +30,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #7995: When calling accept() on a socket with a timeout, the returned
+  socket is now always non-blocking, regardless of the operating system.
+
 - Issue #10756: atexit normalizes the exception before displaying it. Patch by
   Andreas Stührk.