feat: drop C++11 support, require C++14 or newer

.clang-tidy

@@ -21,6 +21,7 @@ Checks: |
   modernize-avoid-bind,
   modernize-loop-convert,
   modernize-make-shared,
+  modernize-make-unique,
   modernize-redundant-void-arg,
   modernize-replace-auto-ptr,
   modernize-replace-disallow-copy-and-assign-macro,
@@ -35,6 +36,7 @@ Checks: |
   modernize-use-noexcept,
   modernize-use-nullptr,
   modernize-use-override,
+  modernize-use-transparent-functors,
   modernize-use-using,
   readability-avoid-const-params-in-decls,
   readability-braces-around-statements,

.github/workflows/ci.yml

@@ -99,7 +99,7 @@ jobs:
             cmake-args: -DCMAKE_CXX_STANDARD=14
           - runs-on: macos-15-intel
             python-version: '3.13'
-            cmake-args: -DCMAKE_CXX_STANDARD=11
+            cmake-args: -DCMAKE_CXX_STANDARD=14
           - runs-on: macos-latest
             python-version: '3.12'
             cmake-args: -DCMAKE_CXX_STANDARD=17 -DPYBIND11_DISABLE_HANDLE_TYPE_NAME_DEFAULT_IMPLEMENTATION=ON
@@ -152,7 +152,7 @@ jobs:
       python-version: ${{ matrix.python-version }}
       cmake-args: ${{ matrix.cmake-args }}
 
-  # This checks inplace builds with C++11
+  # This checks inplace builds with C++14
   inplace:
     if: github.event.pull_request.draft == false
     strategy:
@@ -254,12 +254,15 @@ jobs:
         run: uv tool install ninja
 
       - name: Configure via preset
-        run: cmake --preset venv -DPYBIND11_CREATE_WITH_UV="${{ matrix.python-version }}"
+        run: >
+          cmake --preset venv
+          -DPYBIND11_CREATE_WITH_UV="${{ matrix.python-version }}"
+          -DCMAKE_CXX_STANDARD=14
 
-      - name: Build C++11
+      - name: Build C++14
         run: cmake --build --preset venv
 
-      - name: Python tests C++11
+      - name: Python tests C++14
         run: cmake --build --preset testsvenv -t pytest
 
   # Testing on clang using the excellent silkeh clang docker images
@@ -536,43 +539,43 @@ jobs:
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         python3 -m pip install -r tests/requirements.txt
 
-    - name: Configure C++11
+    - name: Configure C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake -S . -B build-11     \
+        cmake -S . -B build-14     \
         -DPYBIND11_WERROR=ON    \
         -DDOWNLOAD_CATCH=ON     \
         -DDOWNLOAD_EIGEN=OFF    \
-        -DCMAKE_CXX_STANDARD=11             \
+        -DCMAKE_CXX_STANDARD=14             \
         -DCMAKE_CXX_COMPILER=$(which icpc)  \
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
-    - name: Build C++11
+    - name: Build C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-11 -j 2 -v
+        cmake --build build-14 -j 2 -v
 
-    - name: Python tests C++11
+    - name: Python tests C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
         sudo service apport stop
-        cmake --build build-11 --target check
+        cmake --build build-14 --target check
 
-    - name: C++ tests C++11
+    - name: C++ tests C++14
       timeout-minutes: 3
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-11 --target cpptest
+        cmake --build build-14 --target cpptest
 
-    - name: Interface test C++11
+    - name: Interface test C++14
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-11 --target test_cmake_build
+        cmake --build build-14 --target test_cmake_build
 
     - name: Visibility test
       run: |
         set +e; source /opt/intel/oneapi/setvars.sh; set -e
-        cmake --build build-11 --target test_cross_module_rtti
+        cmake --build build-14 --target test_cross_module_rtti
 
     - name: Configure C++17
       run: |
@@ -659,7 +662,7 @@ jobs:
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=11
+        -DCMAKE_CXX_STANDARD=14
         -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
     - name: Build
@@ -810,7 +813,7 @@ jobs:
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         ${{ matrix.args }}
-    - name: Build C++11
+    - name: Build C++14
       run: cmake --build build -j 2
 
     - name: Python tests
@@ -859,7 +862,7 @@ jobs:
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         ${{ matrix.args }}
-    - name: Build C++11
+    - name: Build C++14
       run: cmake --build build --config Debug -j 2
 
     - name: Python tests
@@ -969,25 +972,25 @@ jobs:
 
     - uses: actions/checkout@v7
 
-    - name: Configure C++11
+    - name: Configure C++14
       # 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 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
+        cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
         -S . -B build
 
-    - name: Build C++11
+    - name: Build C++14
       run: cmake --build build -j 2
 
-    - name: Python tests C++11
+    - name: Python tests C++14
       run: cmake --build build --target pytest -j 2
 
-    - name: C++11 tests
+    - name: C++14 tests
       timeout-minutes: 3
       run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build --target cpptest -j 2
 
-    - name: Interface test C++11
+    - name: Interface test C++14
       run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build --target test_cmake_build
 
     - name: Visibility test
@@ -996,31 +999,6 @@ jobs:
     - name: Clean directory
       run: git clean -fdx
 
-    - name: Configure C++14
-      run: >-
-        cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=14 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON
-        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
-        -S . -B build2
-
-    - name: Build C++14
-      run: cmake --build build2 -j 2
-
-    - name: Python tests C++14
-      run: cmake --build build2 --target pytest -j 2
-
-    - name: C++14 tests
-      timeout-minutes: 3
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build2 --target cpptest -j 2
-
-    - name: Interface test C++14
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build2 --target test_cmake_build
-
-    - name: Visibility test
-      run: PYTHONHOME=/${{matrix.sys}} PYTHONPATH=/${{matrix.sys}} cmake --build build2 --target test_cross_module_rtti
-
-    - name: Clean directory
-      run: git clean -fdx
-
     - name: Configure C++17
       run: >-
         cmake -G "MinGW Makefiles" -DCMAKE_CXX_STANDARD=17 -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON

.github/workflows/upstream.yml

@@ -49,28 +49,28 @@ jobs:
         cmake --version
         pip list
 
-    # First build - C++11 mode and inplace
-    - name: Configure C++11
+    # First build - C++14 mode and inplace
+    - name: Configure C++14
       run: >
-        cmake -S . -B build11
+        cmake -S . -B build14
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=11
+        -DCMAKE_CXX_STANDARD=14
         -DCMAKE_BUILD_TYPE=Debug
 
-    - name: Build C++11
-      run: cmake --build build11 -j 2
+    - name: Build C++14
+      run: cmake --build build14 -j 2
 
-    - name: Python tests C++11
-      run: cmake --build build11 --target pytest -j 2
+    - name: Python tests C++14
+      run: cmake --build build14 --target pytest -j 2
 
-    - name: C++11 tests
+    - name: C++14 tests
       timeout-minutes: 3
-      run: cmake --build build11  --target cpptest -j 2
+      run: cmake --build build14  --target cpptest -j 2
 
-    - name: Interface test C++11
-      run: cmake --build build11 --target test_cmake_build
+    - name: Interface test C++14
+      run: cmake --build build14 --target test_cmake_build
 
     # Second build - C++17 mode and in a build directory
     - name: Configure C++17

CMakeLists.txt

@@ -294,8 +294,7 @@ if(NOT TARGET pybind11_headers)
     pybind11_headers ${pybind11_system} INTERFACE $<BUILD_INTERFACE:${pybind11_INCLUDE_DIR}>
                                                   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 
-  target_compile_features(pybind11_headers INTERFACE cxx_inheriting_constructors cxx_user_literals
-                                                     cxx_right_angle_brackets)
+  target_compile_features(pybind11_headers INTERFACE cxx_std_14)
   if(NOT "${PYBIND11_INTERNALS_VERSION}" STREQUAL "")
     target_compile_definitions(
       pybind11_headers INTERFACE "PYBIND11_INTERNALS_VERSION=${PYBIND11_INTERNALS_VERSION}")

docs/advanced/deprecated.rst

@@ -3,8 +3,8 @@
 Deprecated
 ##########
 
-Support for C++11 is deprecated and will be removed in a future version. Please
-use at least C++14.
+Support for C++11 was removed in pybind11 3.1. Please use at least C++14;
+C++17 or newer is recommended.
 
 Support for FindPythonLibs (not available in CMake 3.26+ mode) is deprecated
 and will be removed in a future version. The default mode is also going to

docs/basics.rst

@@ -143,7 +143,7 @@ On Linux, the above example can be compiled using the following command:
 
 .. code-block:: bash
 
-    $ c++ -O3 -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 --includes) example.cpp -o example$(python3 -m pybind11 --extension-suffix)
+    $ c++ -O3 -Wall -shared -std=c++14 -fPIC $(python3 -m pybind11 --includes) example.cpp -o example$(python3 -m pybind11 --extension-suffix)
 
 .. note::
 

docs/classes.rst

@@ -414,8 +414,7 @@ The overload signatures are also visible in the method's docstring:
      |
      |      Set the pet's name
 
-If you have a C++14 compatible compiler [#cpp14]_, you can use an alternative
-syntax to cast the overloaded function:
+You can also use an alternative syntax to cast the overloaded function:
 
 .. code-block:: cpp
 
@@ -439,20 +438,6 @@ on constness, the ``py::const_`` tag should be used:
        .def("foo_mutable", py::overload_cast<int, float>(&Widget::foo))
        .def("foo_const",   py::overload_cast<int, float>(&Widget::foo, py::const_));
 
-If you prefer the ``py::overload_cast`` syntax but have a C++11 compatible compiler only,
-you can use ``py::detail::overload_cast_impl`` with an additional set of parentheses:
-
-.. code-block:: cpp
-
-    template <typename... Args>
-    using overload_cast_ = pybind11::detail::overload_cast_impl<Args...>;
-
-    py::class_<Pet>(m, "Pet")
-        .def("set", overload_cast_<int>()(&Pet::set), "Set the pet's age")
-        .def("set", overload_cast_<const std::string &>()(&Pet::set), "Set the pet's name");
-
-.. [#cpp14] A compiler which supports the ``-std=c++14`` flag.
-
 .. note::
 
     To define multiple overloaded constructors, simply declare one after the

docs/compiling.rst

@@ -78,7 +78,7 @@ that. Your ``meson.build`` file would look something like this:
        'cpp',
        version: '0.1.0',
        default_options: [
-           'cpp_std=c++11',
+           'cpp_std=c++14',
        ],
    )
 
@@ -649,7 +649,7 @@ On Linux, you can compile an example such as the one given in
 
 .. code-block:: bash
 
-    $ c++ -O3 -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 --includes) example.cpp -o example$(python3-config --extension-suffix)
+    $ c++ -O3 -Wall -shared -std=c++14 -fPIC $(python3 -m pybind11 --includes) example.cpp -o example$(python3-config --extension-suffix)
 
 The ``python3 -m pybind11 --includes`` command fetches the include paths for
 both pybind11 and Python headers. This assumes that pybind11 has been installed
@@ -663,7 +663,7 @@ building the module:
 
 .. code-block:: bash
 
-    $ c++ -O3 -Wall -shared -std=c++11 -undefined dynamic_lookup $(python3 -m pybind11 --includes) example.cpp -o example$(python3-config --extension-suffix)
+    $ c++ -O3 -Wall -shared -std=c++14 -undefined dynamic_lookup $(python3 -m pybind11 --includes) example.cpp -o example$(python3-config --extension-suffix)
 
 For quick tests, the command line tool can also produce the full set of flags
 for you, based on ``python-config``:

include/pybind11/attr.h

@@ -677,28 +677,24 @@ struct process_attributes {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
-        (void) expander{
-            0, ((void) process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
+        (void) expander{0, ((void) process_attribute<std::decay_t<Args>>::init(args, r), 0)...};
     }
     static void init(const Args &...args, type_record *r) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(r);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(r);
         using expander = int[];
-        (void) expander{0,
-                        (process_attribute<typename std::decay<Args>::type>::init(args, r), 0)...};
+        (void) expander{0, (process_attribute<std::decay_t<Args>>::init(args, r), 0)...};
     }
     static void precall(function_call &call) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call);
         using expander = int[];
-        (void) expander{0,
-                        (process_attribute<typename std::decay<Args>::type>::precall(call), 0)...};
+        (void) expander{0, (process_attribute<std::decay_t<Args>>::precall(call), 0)...};
     }
     static void postcall(function_call &call, handle fn_ret) {
         PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(call, fn_ret);
         PYBIND11_WORKAROUND_INCORRECT_GCC_UNUSED_BUT_SET_PARAMETER(fn_ret);
         using expander = int[];
-        (void) expander{
-            0, (process_attribute<typename std::decay<Args>::type>::postcall(call, fn_ret), 0)...};
+        (void) expander{0, (process_attribute<std::decay_t<Args>>::postcall(call, fn_ret), 0)...};
     }
 };