From 1c831353816ff699b54e804047a7242a09e98f5b Mon Sep 17 00:00:00 2001
From: rtobar <rtobarc@gmail.com>
Date: Thu, 14 Oct 2021 00:38:36 +0800
Subject: [PATCH] bpo-45386: Handle strftime's ValueError graciously in
 xmlrpc.client (GH-28765)

At import time, the xmlrpc.client module uses different date formats to
test strftime so it can format years with 4 digits consistently.
Depending on the underlying C library and its strftime implementation
some of these calls can result in ValueErrors, blocking the
xmlrpc.client module from being imported.

This commit changes the behavior of this bit of code to react to
ValueError exceptions, treating the format that caused them as an
non-viable option.
---
 Lib/xmlrpc/client.py                                   | 10 ++++++++--
 .../Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst   |  3 +++
 2 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst

diff --git a/Lib/xmlrpc/client.py b/Lib/xmlrpc/client.py
index 9e7449c88df..a614cef6ab2 100644
--- a/Lib/xmlrpc/client.py
+++ b/Lib/xmlrpc/client.py
@@ -264,16 +264,22 @@ def __repr__(self):
 
 # Issue #13305: different format codes across platforms
 _day0 = datetime(1, 1, 1)
-if _day0.strftime('%Y') == '0001':      # Mac OS X
+def _try(fmt):
+    try:
+        return _day0.strftime(fmt) == '0001'
+    except ValueError:
+        return False
+if _try('%Y'):      # Mac OS X
     def _iso8601_format(value):
         return value.strftime("%Y%m%dT%H:%M:%S")
-elif _day0.strftime('%4Y') == '0001':   # Linux
+elif _try('%4Y'):   # Linux
     def _iso8601_format(value):
         return value.strftime("%4Y%m%dT%H:%M:%S")
 else:
     def _iso8601_format(value):
         return value.strftime("%Y%m%dT%H:%M:%S").zfill(17)
 del _day0
+del _try
 
 
 def _strftime(value):
diff --git a/Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst b/Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst
new file mode 100644
index 00000000000..eec77ceccf9
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-10-07-00-05-05.bpo-45386.q9ORpA.rst
@@ -0,0 +1,3 @@
+Make :mod:`xmlrpc.client` more robust to C runtimes where the underlying C
+``strftime`` function results in a ``ValueError`` when testing for year
+formatting options.