From 1ae9cde4b2323235b5f9ff4bc76e4175a2257172 Mon Sep 17 00:00:00 2001
From: Stefan Krah <skrah@bytereef.org>
Date: Thu, 12 Mar 2020 19:35:38 +0100
Subject: [PATCH] bpo-39689: Do not test undefined casts to _Bool (GH-18964)

- When casting to _Bool, arrays should only contain zeros or ones.
---
 Lib/test/test_buffer.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Lib/test/test_buffer.py b/Lib/test/test_buffer.py
index 2ddca06b8b5..d440bcf7e0f 100644
--- a/Lib/test/test_buffer.py
+++ b/Lib/test/test_buffer.py
@@ -2754,6 +2754,10 @@ class TestBufferProtocol(unittest.TestCase):
         # be 1D, at least one format must be 'c', 'b' or 'B'.
         for _tshape in gencastshapes():
             for char in fmtdict['@']:
+                # Casts to _Bool are undefined if the source contains values
+                # other than 0 or 1.
+                if char == "?":
+                    continue
                 tfmt = ('', '@')[randrange(2)] + char
                 tsize = struct.calcsize(tfmt)
                 n = prod(_tshape) * tsize