Issue #8847: Disable COMDAT folding in Windows PGO builds.

Analysis by Victor Stinner. Patch by Stefan Krah.

2 files changed, 16 insertions, 0 deletions

diff --git a/Lib/test/test_list.py b/Lib/test/test_list.py
index d7e6629..84b8afe 100644
--- a/Lib/test/test_list.py
+++ b/Lib/test/test_list.py
@@ -70,6 +70,14 @@ class ListTest(list_tests.CommonTest):
         check(1000000)
 
 
+    def test_no_comdat_folding(self):
+        # Issue 8847: In the PGO build, the MSVC linker's COMDAT folding
+        # optimization causes failures in code that relies on distinct
+        # function addresses.
+        class L(list): pass
+        with self.assertRaises(TypeError):
+            (3,) + L([1,2])
+
 def test_main(verbose=None):
     support.run_unittest(ListTest)
 
diff --git a/Lib/test/test_tuple.py b/Lib/test/test_tuple.py
index 1464a0e..6e934fb 100644
--- a/Lib/test/test_tuple.py
+++ b/Lib/test/test_tuple.py
@@ -164,6 +164,14 @@ class TupleTest(seq_tests.CommonTest):
         check(10)       # check our checking code
         check(1000000)
 
+    def test_no_comdat_folding(self):
+        # Issue 8847: In the PGO build, the MSVC linker's COMDAT folding
+        # optimization causes failures in code that relies on distinct
+        # function addresses.
+        class T(tuple): pass
+        with self.assertRaises(TypeError):
+            [3,] + T((1,2))
+
 def test_main():
     support.run_unittest(TupleTest)