--- ci.yml	2021-12-29 13:23:17.380542309 -0800
+++ ci_sh_def.yml	2021-12-29 13:25:04.832676256 -0800
@@ -1,4 +1,16 @@
-name: CI
+# PLEASE KEEP THIS GROUP OF FILES IN SYNC AT ALL TIMES:
+#     ci.yml
+#     ci_sh_def.yml
+#     ci_sh_def.yml.patch
+# To import changes made to ci.yml *** ESPECIALLY AFTER `git merge master` ***:
+#     patch -i ci_sh_def.yml.patch -o ci_sh_def.yml
+# To update the patch file after making changes to ci_sh.yml:
+#     diff -u ci.yml ci_sh_def.yml > ci_sh_def.yml.patch
+#     git commit -a -m 'Tracking ci.yml changes from master.'
+#
+# Thanks a lot to @rhaschke for PR #2930!
+
+name: "CI-SH-DEF"
 
 on:
   workflow_dispatch:
@@ -11,7 +23,7 @@
       - v*
 
 concurrency:
-  group: test-sh-avl${{ github.ref }}
+  group: test-sh-def-${{ github.ref }}
   cancel-in-progress: true
 
 env:
@@ -108,6 +120,7 @@
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
         ${{ matrix.args }}
 
     - name: Build C++11
@@ -135,6 +148,7 @@
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
         ${{ matrix.args }}
 
     - name: Build
@@ -156,6 +170,7 @@
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT ${{runner.os == 'Windows' && '/GR /EHsc' || ''}}"
         -DPYBIND11_INTERNALS_VERSION=10000000
         "-DPYBIND11_TEST_OVERRIDE=test_call_policies.cpp;test_gil_scoped.cpp;test_thread.cpp"
         ${{ matrix.args }}
@@ -259,6 +274,7 @@
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
 
     - name: Build
       run: cmake --build build -j 2
@@ -313,6 +329,7 @@
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
     - name: Build
@@ -342,7 +359,8 @@
       run: apt-get update && DEBIAN_FRONTEND="noninteractive" apt-get install -y cmake git python3-dev python3-pytest python3-numpy
 
     - name: Configure
-      run: cmake -S . -B build -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
+      run: cmake -S . -B build -DPYBIND11_CUDA_TESTS=ON -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
+
 
     - name: Build
       run: cmake --build build -j2 --verbose
@@ -422,7 +440,7 @@
         cmake3 -S . -B build -DDOWNLOAD_CATCH=ON \
                             -DCMAKE_CXX_STANDARD=11 \
                             -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") \
-                            -DCMAKE_CXX_FLAGS="-Wc,--pending_instantiations=0" \
+                            -DCMAKE_CXX_FLAGS="-Wc,--pending_instantiations=0 -DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT" \
                             -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp;test_virtual_functions.cpp"
 
     # Building before installing Pip should produce a warning but not an error
@@ -481,6 +499,7 @@
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.std }}
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
     - name: Build
@@ -536,6 +555,7 @@
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
         -DCMAKE_CXX_STANDARD=11             \
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"  \
         -DCMAKE_CXX_COMPILER=$(which icpc)  \
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
@@ -568,6 +588,7 @@
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
         -DCMAKE_CXX_STANDARD=14             \
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"  \
         -DCMAKE_CXX_COMPILER=$(which icpc)  \
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
@@ -640,6 +661,7 @@
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
     - name: Build
@@ -690,6 +712,7 @@
         cmake ../pybind11-tests
         -DDOWNLOAD_CATCH=ON
         -DPYBIND11_WERROR=ON
+        -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
       working-directory: /build-tests
 
@@ -782,6 +805,7 @@
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
         ${{ matrix.args }}
     - name: Build C++11
       run: cmake --build build -j 2
@@ -829,6 +853,7 @@
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_FLAGS="/GR /EHsc /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
 
     - name: Build C++14
       run: cmake --build build -j 2
@@ -854,11 +879,11 @@
           - python: 2.7
             std: 17
             args: >
-              -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR"
+              -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
           - python: 3.7
             std: 17
             args: >
-              -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR"
+              -DCMAKE_CXX_FLAGS="/permissive- /EHsc /GR /DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT"
 
     steps:
     - uses: actions/checkout@v2
@@ -927,7 +952,7 @@
     - name: Configure C++11
       # LTO leads to many undefined reference like
       # `pybind11::detail::function_call::function_call(pybind11::detail::function_call&&)
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -S . -B build
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=11 -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT" -S . -B build
 
     - name: Build C++11
       run: cmake --build build -j 2
@@ -945,7 +970,7 @@
       run: git clean -fdx
 
     - name: Configure C++14
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -S . -B build2
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT" -S . -B build2
 
     - name: Build C++14
       run: cmake --build build2 -j 2
@@ -963,7 +988,7 @@
       run: git clean -fdx
 
     - name: Configure C++17
-      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -S . -B build3
+      run: cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DCMAKE_CXX_FLAGS="-DPYBIND11_USE_SMART_HOLDER_AS_DEFAULT" -S . -B build3
 
     - name: Build C++17
       run: cmake --build build3 -j 2