--- cpython/Lib/pty.py	2020-08-15 03:54:52.282519370 -0500
+++ pty.py	2020-08-15 03:55:25.402652373 -0500
@@ -10,6 +10,9 @@
 import os
 import sys
 import tty
+from termios import TIOCGWINSZ, TIOCSWINSZ
+from struct import pack
+from fcntl import ioctl
 
 __all__ = ["openpty","fork","spawn"]
 
@@ -67,7 +70,7 @@
 
     result = os.open(tty_name, os.O_RDWR)
     try:
-        from fcntl import ioctl, I_PUSH
+        from fcntl import I_PUSH
     except ImportError:
         return result
     try:
@@ -77,6 +80,26 @@
         pass
     return result
 
+def _login_tty(fd):
+    """Makes the calling process a session leader, makes fd its
+    controlling terminal, stdin, stdout, and stderr. Closes fd."""
+    # Establish a new session.
+    os.setsid()
+
+    # Make fd the controlling terminal.
+    try:
+        ioctl(fd, termios.TIOCSCTTY)
+    except:
+        tmp_fd = os.open(os.ttyname(fd), os.O_RDWR)
+        os.close(tmp_fd)
+
+    # fd becomes stdin/stdout/stderr.
+    os.dup2(fd, STDIN_FILENO)
+    os.dup2(fd, STDOUT_FILENO)
+    os.dup2(fd, STDERR_FILENO)
+    if (fd > STDERR_FILENO):
+        os.close(fd)
+
 def fork():
     """fork() -> (pid, master_fd)
     Fork and make the child a session leader with a controlling terminal."""
@@ -97,20 +120,8 @@
     master_fd, slave_fd = openpty()
     pid = os.fork()
     if pid == CHILD:
-        # Establish a new session.
-        os.setsid()
         os.close(master_fd)
-
-        # Slave becomes stdin/stdout/stderr of child.
-        os.dup2(slave_fd, STDIN_FILENO)
-        os.dup2(slave_fd, STDOUT_FILENO)
-        os.dup2(slave_fd, STDERR_FILENO)
-        if (slave_fd > STDERR_FILENO):
-            os.close (slave_fd)
-
-        # Explicitly open the tty to make it become a controlling tty.
-        tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR)
-        os.close(tmp_fd)
+        _login_tty(slave_fd)
     else:
         os.close(slave_fd)
 
@@ -127,6 +138,12 @@
     """Default read function."""
     return os.read(fd, 1024)
 
+def _setwinsz(slave_fd):
+    """Sets window size."""
+    w = pack('HHHH', 0, 0, 0, 0)
+    s = ioctl(STDIN_FILENO, TIOCGWINSZ, w)
+    ioctl(slave_fd, TIOCSWINSZ, s)
+
 def _copy(master_fd, master_read=_read, stdin_read=_read):
     """Parent copy loop.
     Copies
@@ -153,10 +170,18 @@
     if type(argv) == type(''):
         argv = (argv,)
     sys.audit('pty.spawn', argv)
-    pid, master_fd = fork()
+    master_fd, slave_fd = openpty()
+    pid = os.fork()
     if pid == CHILD:
+        os.close(master_fd)
+        _login_tty(slave_fd)
         os.execlp(argv[0], *argv)
     try:
+        _setwinsz(slave_fd)
+    except:
+        pass
+    os.close(slave_fd)
+    try:
         mode = tty.tcgetattr(STDIN_FILENO)
         tty.setraw(STDIN_FILENO)
         restore = 1