https://github.com/python/cpython/commit/9ea05d4b8f8a007d57b2b33a4dec26408fe6836b
commit: 9ea05d4b8f8a007d57b2b33a4dec26408fe6836b
branch: main
author: Steve Dower <[email protected]>
committer: chris-eibl <[email protected]>
date: 2026-09-20T07:31:17Z
summary:

gh-153668: Temporarily disable unicodectype.c optimization on WinARM64 due to 
compiler bug (#153669)

* Only disable during Release (not PGO)

* Update PCbuild/pyproject.props

---------

Co-authored-by: Chris Eibl <[email protected]>

files:
M PCbuild/pyproject.props
M PCbuild/pythoncore.vcxproj

diff --git a/PCbuild/pyproject.props b/PCbuild/pyproject.props
index 7435c53e3fdcf9..ca8330c004ccce 100644
--- a/PCbuild/pyproject.props
+++ b/PCbuild/pyproject.props
@@ -40,6 +40,8 @@
     <!-- See 
https://developercommunity.visualstudio.com/t/Regression-in-MSVC-1433-1434-ARM64-co/10224361
 -->
     <MSVCHasBrokenARM64Clamping Condition="$(_VCToolsVersion) == '14.34' or 
$(_VCToolsVersion) == '14.35'">true</MSVCHasBrokenARM64Clamping>
     <MSVCHasBrokenARM64SignExtension Condition="$(_VCToolsVersion) == 
'14.37'">true</MSVCHasBrokenARM64SignExtension>
+    <!-- See gh-153668 and 
https://developercommunity.visualstudio.com/t/ARM64-compiler-uses-excessive-memory-on/11120089
 -->
+    <MSVCHasBrokenARM64UniDbOpt Condition="$(_VCToolsVersion) == '14.50' or 
$(_VCToolsVersion) == '14.51'">true</MSVCHasBrokenARM64UniDbOpt>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 0fcd8aeac66473..e4766fd7e5f764 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -583,7 +583,10 @@
     <ClCompile Include="..\Objects\typeobject.c" />
     <ClCompile Include="..\Objects\typevarobject.c" />
     <ClCompile Include="..\Objects\unicode_format.c" />
-    <ClCompile Include="..\Objects\unicodectype.c" />
+    <ClCompile Include="..\Objects\unicodectype.c">
+      <!-- gh-153668: Temporarily disabled due to a compiler bug -->
+      <Optimization Condition="$(Platform) == 'ARM64' and $(Configuration) == 
'Release' and $(MSVCHasBrokenARM64UniDbOpt) == 'true'">Disabled</Optimization>
+    </ClCompile>
     <ClCompile Include="..\Objects\unicode_formatter.c" />
     <ClCompile Include="..\Objects\unicode_writer.c" />
     <ClCompile Include="..\Objects\unicodeobject.c" />

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