From 3e1e4f11dd0a2f02b36d931ee61d5d93195cbb7c Mon Sep 17 00:00:00 2001
From: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>
Date: Tue, 25 Mar 2025 19:09:36 +0100
Subject: [PATCH 1/4] use /EHa when compiling with clang-cl

---
 PCbuild/pyproject-clangcl.props |  8 ++++++++
 PCbuild/pyproject.props         | 10 +++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/PCbuild/pyproject-clangcl.props b/PCbuild/pyproject-clangcl.props
index d949c37d562594..a574cf84ee5d6c 100644
--- a/PCbuild/pyproject-clangcl.props
+++ b/PCbuild/pyproject-clangcl.props
@@ -38,6 +38,14 @@
 
   <ItemDefinitionGroup>
     <ClCompile>
+      <!--
+      ExceptionHandling=Async sets MSVC's /EHa (-fasync-exceptions in clang)
+      For clang, /EHa just has a slightly different meaning compared to MSVC,
+      so this option is needed to handle SEH correctly
+      (even though MSVC does not need it).
+      Please see GH-131691 for details.
+      -->
+      <ExceptionHandling>Async</ExceptionHandling>
       <AdditionalOptions>-Wno-deprecated-non-prototype -Wno-unused-label -Wno-pointer-sign -Wno-incompatible-pointer-types-discards-qualifiers -Wno-unused-function %(AdditionalOptions)</AdditionalOptions>
       <AdditionalOptions Condition="'$(Platform)' == 'Win32'">-m32 %(AdditionalOptions)</AdditionalOptions>
       <AdditionalOptions Condition="'$(Platform)' == 'x64'">-m64 %(AdditionalOptions)</AdditionalOptions>
diff --git a/PCbuild/pyproject.props b/PCbuild/pyproject.props
index b5a236ee3e37d5..4e414dc913b9d5 100644
--- a/PCbuild/pyproject.props
+++ b/PCbuild/pyproject.props
@@ -25,9 +25,6 @@
     <LinkIncremental Condition="$(Configuration) != 'Debug'">false</LinkIncremental>
   </PropertyGroup>
 
-  <!-- We need the above overridden OutDir, so this must be imported after PropertyGroup -->
-  <Import Project="pyproject-clangcl.props" Condition="$(PlatformToolset) == 'ClangCL' and $(__PyprojectClangCl_Props_Imported) != 'true'" />
-
   <PropertyGroup Condition="$(TargetExt) != ''">
     <TargetNameExt>$(TargetName)$(TargetExt)</TargetNameExt>
     <_TargetNameSep>$(TargetNameExt.LastIndexOf(`.`))</_TargetNameSep>
@@ -130,6 +127,13 @@
     </Midl>
   </ItemDefinitionGroup>
 
+  <!--
+  We need the overridden OutDir (PropertyGroup Label="Globals"),
+  and want to be able to override some ClCompile parameters,
+  so this must not be included erlier.
+  -->
+  <Import Project="pyproject-clangcl.props" Condition="$(PlatformToolset) == 'ClangCL' and $(__PyprojectClangCl_Props_Imported) != 'true'" />
+
   <UsingTask TaskName="KillPython" TaskFactory="CodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll">
     <ParameterGroup>
       <FileName Required="true" />

From 01335b17c4dcffb09f7aa391aeb8cad9a66e78bd Mon Sep 17 00:00:00 2001
From: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>
Date: Tue, 25 Mar 2025 19:14:46 +0100
Subject: [PATCH 2/4] blurb it

---
 .../next/Build/2025-03-25-19-14-24.gh-issue-131691.2BgHU5.rst   | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Build/2025-03-25-19-14-24.gh-issue-131691.2BgHU5.rst

diff --git a/Misc/NEWS.d/next/Build/2025-03-25-19-14-24.gh-issue-131691.2BgHU5.rst b/Misc/NEWS.d/next/Build/2025-03-25-19-14-24.gh-issue-131691.2BgHU5.rst
new file mode 100644
index 00000000000000..b9567643cdb110
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2025-03-25-19-14-24.gh-issue-131691.2BgHU5.rst
@@ -0,0 +1,2 @@
+clang-cl on Windows needs option ``/EHa`` to support SEH (structured
+exception handling) correctly. Fix by Chris Eibl.

From bd83c140b6d60af2c4780cded17a0a96aef020e9 Mon Sep 17 00:00:00 2001
From: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>
Date: Tue, 25 Mar 2025 19:15:28 +0100
Subject: [PATCH 3/4] temporarily touch (fix) tail-call.yml to trigger CI

---
 .github/workflows/tail-call.yml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/tail-call.yml b/.github/workflows/tail-call.yml
index 3bee758e2ad2cf..d6337482df24d3 100644
--- a/.github/workflows/tail-call.yml
+++ b/.github/workflows/tail-call.yml
@@ -87,8 +87,9 @@ jobs:
           set PlatformToolset=clangcl
           set LLVMToolsVersion=${{ matrix.llvm }}.1.5
           set LLVMInstallDir=C:\Program Files\LLVM
-          ./PCbuild/build.bat --tail-call-interp -d -p ${{ matrix.architecture }}
-          ./PCbuild/rt.bat -d -p ${{ matrix.architecture }} -q --multiprocess 0 --timeout 4500 --verbose2 --verbose3
+          # DO NOT MERGE! Just triggering tail-call Windows CI and invoking tests
+          call ./PCbuild/build.bat --tail-call-interp -d -p ${{ matrix.architecture }}
+          call ./PCbuild/rt.bat -d -p ${{ matrix.architecture }} -q --multiprocess 0 --timeout 4500 --verbose2 --verbose3
 
       # No tests (yet):
       - name: Emulated Windows (release)

From 78cb6d9c39ce4015e8721a5b16b93512afb6adec Mon Sep 17 00:00:00 2001
From: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>
Date: Tue, 25 Mar 2025 20:00:02 +0100
Subject: [PATCH 4/4] Revert "temporarily touch (fix) tail-call.yml to trigger
 CI"

This reverts commit bd83c140b6d60af2c4780cded17a0a96aef020e9.
---
 .github/workflows/tail-call.yml | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/tail-call.yml b/.github/workflows/tail-call.yml
index d6337482df24d3..3bee758e2ad2cf 100644
--- a/.github/workflows/tail-call.yml
+++ b/.github/workflows/tail-call.yml
@@ -87,9 +87,8 @@ jobs:
           set PlatformToolset=clangcl
           set LLVMToolsVersion=${{ matrix.llvm }}.1.5
           set LLVMInstallDir=C:\Program Files\LLVM
-          # DO NOT MERGE! Just triggering tail-call Windows CI and invoking tests
-          call ./PCbuild/build.bat --tail-call-interp -d -p ${{ matrix.architecture }}
-          call ./PCbuild/rt.bat -d -p ${{ matrix.architecture }} -q --multiprocess 0 --timeout 4500 --verbose2 --verbose3
+          ./PCbuild/build.bat --tail-call-interp -d -p ${{ matrix.architecture }}
+          ./PCbuild/rt.bat -d -p ${{ matrix.architecture }} -q --multiprocess 0 --timeout 4500 --verbose2 --verbose3
 
       # No tests (yet):
       - name: Emulated Windows (release)