Merge 7a3a51435e into 1f8b4a7f1a

Bumps the actions group with 1 update: [pypa/cibuildwheel](https://github.com/pypa/cibuildwheel).


Updates `pypa/cibuildwheel` from 2.20 to 2.21
- [Release notes](https://github.com/pypa/cibuildwheel/releases)
- [Changelog](https://github.com/pypa/cibuildwheel/blob/main/docs/changelog.md)
- [Commits](https://github.com/pypa/cibuildwheel/compare/v2.20...v2.21)

---
updated-dependencies:
- dependency-name: pypa/cibuildwheel
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/CONTRIBUTING.md

@@ -81,7 +81,7 @@ nox -s build
 ### Full setup
 
 To setup an ideal development environment, run the following commands on a
-system with CMake 3.14+:
+system with CMake 3.15+:
 
 ```bash
 python3 -m venv venv
@@ -96,8 +96,8 @@ Tips:
 * You can use `virtualenv` (faster, from PyPI) instead of `venv`.
 * You can select any name for your environment folder; if it contains "env" it
   will be ignored by git.
-* If you don't have CMake 3.14+, just add "cmake" to the pip install command.
-* You can use `-DPYBIND11_FINDPYTHON=ON` to use FindPython on CMake 3.12+
+* If you don't have CMake 3.15+, just add "cmake" to the pip install command.
+* You can use `-DPYBIND11_FINDPYTHON=ON` to use FindPython.
 * In classic mode, you may need to set `-DPYTHON_EXECUTABLE=/path/to/python`.
   FindPython uses `-DPython_ROOT_DIR=/path/to` or
   `-DPython_EXECUTABLE=/path/to/python`.
@@ -149,8 +149,8 @@ To run the tests, you can "build" the check target:
 cmake --build build --target check
 ```
 
-`--target` can be spelled `-t` in CMake 3.15+. You can also run individual
-tests with these targets:
+`--target` can be spelled `-t`. You can also run individual tests with these
+targets:
 
 * `pytest`: Python tests only, using the
 [pytest](https://docs.pytest.org/en/stable/) framework

.github/workflows/ci.yml

@@ -243,7 +243,7 @@ jobs:
     - uses: actions/checkout@v4
 
     - name: Setup Python ${{ matrix.python-version }} (deadsnakes)
-      uses: deadsnakes/action@v3.1.0
+      uses: deadsnakes/action@v3.2.0
       with:
         python-version: ${{ matrix.python-version }}
         debug: ${{ matrix.python-debug }}

.github/workflows/configure.yml

@@ -31,7 +31,7 @@ jobs:
         include:
         - runs-on: ubuntu-20.04
           arch: x64
-          cmake: "3.5"
+          cmake: "3.15"
 
         - runs-on: ubuntu-20.04
           arch: x64
@@ -39,7 +39,7 @@ jobs:
 
         - runs-on: macos-13
           arch: x64
-          cmake: "3.8"
+          cmake: "3.15"
 
         - runs-on: windows-2019
           arch: x64 # x86 compilers seem to be missing on 2019 image

.github/workflows/emscripten.yaml

@@ -22,7 +22,7 @@ jobs:
         submodules: true
         fetch-depth: 0
 
-    - uses: pypa/cibuildwheel@v2.20
+    - uses: pypa/cibuildwheel@v2.21
       env:
         PYODIDE_BUILD_EXPORTS: whole_archive
       with:

.github/workflows/pip.yml

@@ -91,18 +91,19 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event_name == 'release' && github.event.action == 'published'
     needs: [packaging]
-    environment: pypi
+    environment:
+      name: pypi
+      url: https://pypi.org/p/pybind11
     permissions:
       id-token: write
       attestations: write
-      contents: read
 
     steps:
     # Downloads all to directories matching the artifact names
     - uses: actions/download-artifact@v4
 
     - name: Generate artifact attestation for sdist and wheel
-      uses: actions/attest-build-provenance@310b0a4a3b0b78ef57ecda988ee04b132db73ef8 # v1.4.1
+      uses: actions/attest-build-provenance@1c608d11d69870c2092266b3f9a6f3abbf17002c # v1.4.3
       with:
         subject-path: "*/pybind11*"
 
@@ -110,8 +111,10 @@ jobs:
       uses: pypa/gh-action-pypi-publish@release/v1
       with:
         packages-dir: standard/
+        attestations: true
 
     - name: Publish global package
       uses: pypa/gh-action-pypi-publish@release/v1
       with:
         packages-dir: global/
+        attestations: true

.pre-commit-config.yaml

@@ -32,7 +32,7 @@ repos:
 
 # Ruff, the Python auto-correcting linter/formatter written in Rust
 - repo: https://github.com/astral-sh/ruff-pre-commit
-  rev: v0.5.6
+  rev: v0.6.3
   hooks:
   - id: ruff
     args: ["--fix", "--show-fixes"]
@@ -40,7 +40,7 @@ repos:
 
 # Check static types with mypy
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: "v1.11.1"
+  rev: "v1.11.2"
   hooks:
   - id: mypy
     args: []
@@ -93,7 +93,7 @@ repos:
 
 # Avoid directional quotes
 - repo: https://github.com/sirosen/texthooks
-  rev: "0.6.6"
+  rev: "0.6.7"
   hooks:
   - id: fix-ligatures
   - id: fix-smartquotes
@@ -142,14 +142,14 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v3.2.6"
+  rev: "v3.2.7"
   hooks:
   - id: pylint
     files: ^pybind11
 
 # Check schemas on some of our YAML files
 - repo: https://github.com/python-jsonschema/check-jsonschema
-  rev: 0.29.1
+  rev: 0.29.2
   hooks:
   - id: check-readthedocs
   - id: check-github-workflows

CMakeLists.txt

@@ -10,16 +10,7 @@ if(NOT CMAKE_VERSION VERSION_LESS "3.27")
   cmake_policy(GET CMP0148 _pybind11_cmp0148)
 endif()
 
-cmake_minimum_required(VERSION 3.5)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 if(_pybind11_cmp0148)
   cmake_policy(SET CMP0148 ${_pybind11_cmp0148})
@@ -27,9 +18,7 @@ if(_pybind11_cmp0148)
 endif()
 
 # Avoid infinite recursion if tests include this as a subdirectory
-if(DEFINED PYBIND11_MASTER_PROJECT)
-  return()
-endif()
+include_guard(GLOBAL)
 
 # Extract project version from source
 file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/include/pybind11/detail/common.h"
@@ -74,14 +63,6 @@ if(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
 
   set(PYBIND11_MASTER_PROJECT ON)
 
-  if(OSX AND CMAKE_VERSION VERSION_LESS 3.7)
-    # Bug in macOS CMake < 3.7 is unable to download catch
-    message(WARNING "CMAKE 3.7+ needed on macOS to download catch, and newer HIGHLY recommended")
-  elseif(WINDOWS AND CMAKE_VERSION VERSION_LESS 3.8)
-    # Only tested with 3.8+ in CI.
-    message(WARNING "CMAKE 3.8+ tested on Windows, previous versions untested")
-  endif()
-
   message(STATUS "CMake ${CMAKE_VERSION}")
 
   if(CMAKE_CXX_STANDARD)
@@ -133,8 +114,7 @@ cmake_dependent_option(
   "Install pybind11 headers in Python include directory instead of default installation prefix"
   OFF "PYBIND11_INSTALL" OFF)
 
-cmake_dependent_option(PYBIND11_FINDPYTHON "Force new FindPython" ${_pybind11_findpython_default}
-                       "NOT CMAKE_VERSION VERSION_LESS 3.12" OFF)
+option(PYBIND11_FINDPYTHON "Force new FindPython" ${_pybind11_findpython_default})
 
 # Allow PYTHON_EXECUTABLE if in FINDPYTHON mode and building pybind11's tests
 # (makes transition easier while we support both modes).
@@ -149,12 +129,14 @@ endif()
 set(PYBIND11_HEADERS
     include/pybind11/detail/class.h
     include/pybind11/detail/common.h
+    include/pybind11/detail/cpp_conduit.h
     include/pybind11/detail/descr.h
     include/pybind11/detail/init.h
     include/pybind11/detail/internals.h
     include/pybind11/detail/type_caster_base.h
     include/pybind11/detail/typeid.h
     include/pybind11/detail/value_and_holder.h
+    include/pybind11/detail/exception_translation.h
     include/pybind11/attr.h
     include/pybind11/buffer_info.h
     include/pybind11/cast.h
@@ -180,10 +162,11 @@ set(PYBIND11_HEADERS
     include/pybind11/stl_bind.h
     include/pybind11/stl/filesystem.h
     include/pybind11/type_caster_pyobject_ptr.h
-    include/pybind11/typing.h)
+    include/pybind11/typing.h
+    include/pybind11/warnings.h)
 
 # Compare with grep and warn if mismatched
-if(PYBIND11_MASTER_PROJECT AND NOT CMAKE_VERSION VERSION_LESS 3.12)
+if(PYBIND11_MASTER_PROJECT)
   file(
     GLOB_RECURSE _pybind11_header_check
     LIST_DIRECTORIES false
@@ -201,10 +184,7 @@ if(PYBIND11_MASTER_PROJECT AND NOT CMAKE_VERSION VERSION_LESS 3.12)
   endif()
 endif()
 
-# CMake 3.12 added list(TRANSFORM <list> PREPEND
-# But we can't use it yet
-string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/" PYBIND11_HEADERS
-               "${PYBIND11_HEADERS}")
+list(TRANSFORM PYBIND11_HEADERS PREPEND "${CMAKE_CURRENT_SOURCE_DIR}/")
 
 # Cache variable so this can be used in parent projects
 set(pybind11_INCLUDE_DIR
@@ -274,25 +254,11 @@ if(PYBIND11_INSTALL)
     tools/${PROJECT_NAME}Config.cmake.in "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
     INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
 
-  if(CMAKE_VERSION VERSION_LESS 3.14)
-    # Remove CMAKE_SIZEOF_VOID_P from ConfigVersion.cmake since the library does
-    # not depend on architecture specific settings or libraries.
-    set(_PYBIND11_CMAKE_SIZEOF_VOID_P ${CMAKE_SIZEOF_VOID_P})
-    unset(CMAKE_SIZEOF_VOID_P)
-
-    write_basic_package_version_file(
-      ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-      VERSION ${PROJECT_VERSION}
-      COMPATIBILITY AnyNewerVersion)
-
-    set(CMAKE_SIZEOF_VOID_P ${_PYBIND11_CMAKE_SIZEOF_VOID_P})
-  else()
-    # CMake 3.14+ natively supports header-only libraries
+  # CMake natively supports header-only libraries
   write_basic_package_version_file(
     ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
     VERSION ${PROJECT_VERSION}
     COMPATIBILITY AnyNewerVersion ARCH_INDEPENDENT)
-  endif()
 
   install(
     FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake

docs/advanced/cast/stl.rst

@@ -162,7 +162,7 @@ the declaration
 
 .. code-block:: cpp
 
-    PYBIND11_MAKE_OPAQUE(std::vector<int>);
+    PYBIND11_MAKE_OPAQUE(std::vector<int>)
 
 before any binding code (e.g. invocations to ``class_::def()``, etc.). This
 macro must be specified at the top level (and outside of any namespaces), since
@@ -207,8 +207,8 @@ The following example showcases usage of :file:`pybind11/stl_bind.h`:
     // Don't forget this
     #include <pybind11/stl_bind.h>
 
-    PYBIND11_MAKE_OPAQUE(std::vector<int>);
-    PYBIND11_MAKE_OPAQUE(std::map<std::string, double>);
+    PYBIND11_MAKE_OPAQUE(std::vector<int>)
+    PYBIND11_MAKE_OPAQUE(std::map<std::string, double>)
 
     // ...
 

docs/advanced/embedding.rst

@@ -18,7 +18,7 @@ information, see :doc:`/compiling`.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.5...3.29)
+    cmake_minimum_required(VERSION 3.15...3.30)
     project(example)
 
     find_package(pybind11 REQUIRED)  # or `add_subdirectory(pybind11)`

docs/advanced/smart_ptrs.rst

@@ -124,7 +124,7 @@ top namespace level before any binding code:
 
 .. code-block:: cpp
 
-    PYBIND11_DECLARE_HOLDER_TYPE(T, SmartPtr<T>);
+    PYBIND11_DECLARE_HOLDER_TYPE(T, SmartPtr<T>)
 
 The first argument of :func:`PYBIND11_DECLARE_HOLDER_TYPE` should be a
 placeholder name that is used as a template parameter of the second argument.
@@ -136,7 +136,7 @@ by default. Specify
 
 .. code-block:: cpp
 
-    PYBIND11_DECLARE_HOLDER_TYPE(T, SmartPtr<T>, true);
+    PYBIND11_DECLARE_HOLDER_TYPE(T, SmartPtr<T>, true)
 
 if ``SmartPtr<T>`` can always be initialized from a ``T*`` pointer without the
 risk of inconsistencies (such as multiple independent ``SmartPtr`` instances
@@ -154,7 +154,7 @@ specialized:
 .. code-block:: cpp
 
     // Always needed for custom holder types
-    PYBIND11_DECLARE_HOLDER_TYPE(T, SmartPtr<T>);
+    PYBIND11_DECLARE_HOLDER_TYPE(T, SmartPtr<T>)
 
     // Only needed if the type's `.get()` goes by another name
     namespace PYBIND11_NAMESPACE { namespace detail {

docs/basics.rst

@@ -78,6 +78,13 @@ For brevity, all code examples assume that the following two lines are present:
 
     namespace py = pybind11;
 
+.. note::
+
+    ``pybind11/pybind11.h`` includes ``Python.h``, as such it must be the first file
+    included in any source file or header for `the same reasons as Python.h`_.
+
+.. _`the same reasons as Python.h`: https://docs.python.org/3/extending/extending.html#a-simple-example
+
 Some features may require additional headers, but those will be specified as needed.
 
 .. _simple_example:

docs/changelog.rst

@@ -20,7 +20,76 @@ New Features:
 * Support for Python 3.7 was removed. (Official end-of-life: 2023-06-27).
   `#5191 <https://github.com/pybind/pybind11/pull/5191>`_
 
-Support for CMake older than 3.15 and some older compilers will also be removed.
+* stl.h ``list|set|map_caster`` were made more user friendly: it is no longer
+  necessary to explicitly convert Python iterables to ``tuple()``, ``set()``,
+  or ``map()`` in many common situations.
+  `#4686 <https://github.com/pybind/pybind11/pull/4686>`_
+
+* Support for CMake older than 3.15 removed. CMake 3.15-3.30 supported.
+  `#5304 <https://github.com/pybind/pybind11/pull/5304>`_
+
+* The ``array_caster`` in pybind11/stl.h was enhanced to support value types that are not default-constructible.
+  `#5305 <https://github.com/pybind/pybind11/pull/5305>`_
+
+* Added ``py::warnings`` namespace with ``py::warnings::warn`` and ``py::warnings::new_warning_type`` that provides the interface for Python warnings.
+  `#5291 <https://github.com/pybind/pybind11/pull/5291>`_
+
+Version 2.13.6 (September 13, 2024)
+-----------------------------------
+
+New Features:
+
+* A new ``self._pybind11_conduit_v1_()`` method is automatically added to all
+  ``py::class_``-wrapped types, to enable type-safe interoperability between
+  different independent Python/C++ bindings systems, including pybind11
+  versions with different ``PYBIND11_INTERNALS_VERSION``'s. Supported on
+  pybind11 2.11.2, 2.12.1, and 2.13.6+.
+  `#5296 <https://github.com/pybind/pybind11/pull/5296>`_
+
+
+Bug fixes:
+
+* Using ``__cpp_nontype_template_args`` instead of ``__cpp_nontype_template_parameter_class``.
+  `#5330 <https://github.com/pybind/pybind11/pull/5330>`_
+
+* Properly translate C++ exception to Python exception when creating Python buffer from wrapped object.
+  `#5324 <https://github.com/pybind/pybind11/pull/5324>`_
+
+
+Documentation:
+
+* Adds an answer (FAQ) for "What is a highly conclusive and simple way to find memory leaks?".
+  `#5340 <https://github.com/pybind/pybind11/pull/5340>`_
+
+
+Version 2.13.5 (August 22, 2024)
+--------------------------------
+
+Bug fixes:
+
+* Fix includes when using Windows long paths (``\\?\`` prefix).
+  `#5321 <https://github.com/pybind/pybind11/pull/5321>`_
+
+* Support ``-Wpedantic`` in C++20 mode.
+  `#5322 <https://github.com/pybind/pybind11/pull/5322>`_
+
+* Fix and test ``<ranges>`` support for ``py::tuple`` and ``py::list``.
+  `#5314 <https://github.com/pybind/pybind11/pull/5314>`_
+
+Version 2.13.4 (August 14, 2024)
+--------------------------------
+
+Bug fixes:
+
+* Fix paths with spaces, including on Windows.
+  (Replaces regression from `#5302 <https://github.com/pybind/pybind11/pull/5302>`_)
+  `#4874 <https://github.com/pybind/pybind11/pull/4874>`_
+
+Documentation:
+
+* Remove repetitive words.
+  `#5308 <https://github.com/pybind/pybind11/pull/5308>`_
+
 
 Version 2.13.3 (August 13, 2024)
 --------------------------------
@@ -200,6 +269,18 @@ Other:
 * Update docs and noxfile.
   `#5071 <https://github.com/pybind/pybind11/pull/5071>`_
 
+Version 2.12.1 (September 13, 2024)
+-----------------------------------
+
+New Features:
+
+* A new ``self._pybind11_conduit_v1_()`` method is automatically added to all
+  ``py::class_``-wrapped types, to enable type-safe interoperability between
+  different independent Python/C++ bindings systems, including pybind11
+  versions with different ``PYBIND11_INTERNALS_VERSION``'s. Supported on
+  pybind11 2.11.2, 2.12.1, and 2.13.6+.
+  `#5296 <https://github.com/pybind/pybind11/pull/5296>`_
+
 
 Version 2.12.0 (March 27, 2024)
 -------------------------------
@@ -375,6 +456,18 @@ Other:
 * An ``assert()`` was added to help Coverty avoid generating a false positive.
   `#4817 <https://github.com/pybind/pybind11/pull/4817>`_
 
+Version 2.11.2 (September 13, 2024)
+-----------------------------------
+
+New Features:
+
+* A new ``self._pybind11_conduit_v1_()`` method is automatically added to all
+  ``py::class_``-wrapped types, to enable type-safe interoperability between
+  different independent Python/C++ bindings systems, including pybind11
+  versions with different ``PYBIND11_INTERNALS_VERSION``'s. Supported on
+  pybind11 2.11.2, 2.12.1, and 2.13.6+.
+  `#5296 <https://github.com/pybind/pybind11/pull/5296>`_
+
 
 Version 2.11.1 (July 17, 2023)
 ------------------------------

docs/compiling.rst

@@ -18,7 +18,7 @@ A Python extension module can be created with just a few lines of code:
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.15...3.29)
+    cmake_minimum_required(VERSION 3.15...3.30)
     project(example LANGUAGES CXX)
 
     set(PYBIND11_FINDPYTHON ON)
@@ -319,11 +319,11 @@ Building with CMake
 
 For C++ codebases that have an existing CMake-based build system, a Python
 extension module can be created with just a few lines of code, as seen above in
-the module section. Pybind11 currently supports a lower minimum if you don't
-use the modern FindPython, though be aware that CMake 3.27 removed the old
-mechanism, so pybind11 will automatically switch if the old mechanism is not
-available. Please opt into the new mechanism if at all possible. Our default
-may change in future versions. This is the minimum required:
+the module section. Pybind11 currently defaults to the old mechanism, though be
+aware that CMake 3.27 removed the old mechanism, so pybind11 will automatically
+switch if the old mechanism is not available. Please opt into the new mechanism
+if at all possible. Our default may change in future versions. This is the
+minimum required:
 
 
 
@@ -333,6 +333,9 @@ may change in future versions. This is the minimum required:
 .. versionchanged:: 2.11
    CMake 3.5+ is required.
 
+.. versionchanged:: 2.14
+   CMake 3.15+ is required.
+
 
 Further information can be found at :doc:`cmake/index`.
 
@@ -444,7 +447,7 @@ See the `Config file`_ docstring for details of relevant CMake variables.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.4...3.18)
+    cmake_minimum_required(VERSION 3.15...3.30)
     project(example LANGUAGES CXX)
 
     find_package(pybind11 REQUIRED)
@@ -483,14 +486,13 @@ can refer to the same [cmake_example]_ repository for a full sample project
 FindPython mode
 ---------------
 
-CMake 3.12+ (3.15+ recommended, 3.18.2+ ideal) added a new module called
-FindPython that had a highly improved search algorithm and modern targets
-and tools. If you use FindPython, pybind11 will detect this and use the
-existing targets instead:
+Modern CMake (3.18.2+ ideal) added a new module called FindPython that had a
+highly improved search algorithm and modern targets and tools. If you use
+FindPython, pybind11 will detect this and use the existing targets instead:
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.15...3.22)
+    cmake_minimum_required(VERSION 3.15...3.30)
     project(example LANGUAGES CXX)
 
     find_package(Python 3.8 COMPONENTS Interpreter Development REQUIRED)
@@ -541,7 +543,7 @@ available in all modes. The targets provided are:
      Just the "linking" part of pybind11:module
 
    ``pybind11::module``
-     Everything for extension modules - ``pybind11::pybind11`` + ``Python::Module`` (FindPython CMake 3.15+) or ``pybind11::python_link_helper``
+     Everything for extension modules - ``pybind11::pybind11`` + ``Python::Module`` (FindPython) or ``pybind11::python_link_helper``
 
    ``pybind11::embed``
      Everything for embedding the Python interpreter - ``pybind11::pybind11`` + ``Python::Python`` (FindPython) or Python libs
@@ -568,7 +570,7 @@ You can use these targets to build complex applications. For example, the
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.5...3.29)
+    cmake_minimum_required(VERSION 3.15...3.30)
     project(example LANGUAGES CXX)
 
     find_package(pybind11 REQUIRED)  # or add_subdirectory(pybind11)
@@ -626,7 +628,7 @@ information about usage in C++, see :doc:`/advanced/embedding`.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.5...3.29)
+    cmake_minimum_required(VERSION 3.15...3.30)
     project(example LANGUAGES CXX)
 
     find_package(pybind11 REQUIRED)  # or add_subdirectory(pybind11)

docs/faq.rst

@@ -247,6 +247,50 @@ been received, you must either explicitly interrupt execution by throwing
         });
     }
 
+What is a highly conclusive and simple way to find memory leaks (e.g. in pybind11 bindings)?
+============================================================================================
+
+Use ``while True`` & ``top`` (Linux, macOS).
+
+For example, locally change tests/test_type_caster_pyobject_ptr.py like this:
+
+.. code-block:: diff
+
+     def test_return_list_pyobject_ptr_reference():
+    +  while True:
+         vec_obj = m.return_list_pyobject_ptr_reference(ValueHolder)
+         assert [e.value for e in vec_obj] == [93, 186]
+         # Commenting out the next `assert` will leak the Python references.
+         # An easy way to see evidence of the leaks:
+         # Insert `while True:` as the first line of this function and monitor the
+         # process RES (Resident Memory Size) with the Unix top command.
+    -    assert m.dec_ref_each_pyobject_ptr(vec_obj) == 2
+    +    # assert m.dec_ref_each_pyobject_ptr(vec_obj) == 2
+
+Then run the test as you would normally do, which will go into the infinite loop.
+
+**In another shell, but on the same machine** run:
+
+.. code-block:: bash
+
+    top
+
+This will show:
+
+.. code-block::
+
+        PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
+    1266095 rwgk      20   0 5207496 611372  45696 R 100.0   0.3   0:08.01 test_type_caste
+
+Look for the number under ``RES`` there. You'll see it going up very quickly.
+
+**Don't forget to Ctrl-C the test command** before your machine becomes
+unresponsive due to swapping.
+
+This method only takes a couple minutes of effort and is very conclusive.
+What you want to see is that the ``RES`` number is stable after a couple
+seconds.
+
 CMake doesn't detect the right Python version
 =============================================
 
@@ -258,9 +302,9 @@ CMake configure line. (Replace ``$(which python)`` with a path to python if
 your prefer.)
 
 You can alternatively try ``-DPYBIND11_FINDPYTHON=ON``, which will activate the
-new CMake FindPython support instead of pybind11's custom search. Requires
-CMake 3.12+, and 3.15+ or 3.18.2+ are even better. You can set this in your
-``CMakeLists.txt`` before adding or finding pybind11, as well.
+new CMake FindPython support instead of pybind11's custom search. Newer CMake,
+like, 3.18.2+, is recommended. You can set this in your ``CMakeLists.txt``
+before adding or finding pybind11, as well.
 
 Inconsistent detection of Python version in CMake and pybind11
 ==============================================================
@@ -281,11 +325,11 @@ There are three possible solutions:
    from CMake and rely on pybind11 in detecting Python version. If this is not
    possible, the CMake machinery should be called *before* including pybind11.
 2. Set ``PYBIND11_FINDPYTHON`` to ``True`` or use ``find_package(Python
-   COMPONENTS Interpreter Development)`` on modern CMake (3.12+, 3.15+ better,
-   3.18.2+ best). Pybind11 in these cases uses the new CMake FindPython instead
-   of the old, deprecated search tools, and these modules are much better at
-   finding the correct Python. If FindPythonLibs/Interp are not available
-   (CMake 3.27+), then this will be ignored and FindPython will be used.
+   COMPONENTS Interpreter Development)`` on modern CMake ( 3.18.2+ best).
+   Pybind11 in these cases uses the new CMake FindPython instead of the old,
+   deprecated search tools, and these modules are much better at finding the
+   correct Python. If FindPythonLibs/Interp are not available (CMake 3.27+),
+   then this will be ignored and FindPython will be used.
 3. Set ``PYBIND11_NOPYTHON`` to ``TRUE``. Pybind11 will not search for Python.
    However, you will have to use the target-based system, and do more setup
    yourself, because it does not know about or include things that depend on

include/pybind11/detail/class.h

@@ -9,8 +9,10 @@
 
 #pragma once
 
-#include "../attr.h"
-#include "../options.h"
+#include <pybind11/attr.h>
+#include <pybind11/options.h>
+
+#include "exception_translation.h"
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -581,7 +583,18 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
         return -1;
     }
     std::memset(view, 0, sizeof(Py_buffer));
-    buffer_info *info = tinfo->get_buffer(obj, tinfo->get_buffer_data);
+    buffer_info *info = nullptr;
+    try {
+        info = tinfo->get_buffer(obj, tinfo->get_buffer_data);
+    } catch (...) {
+        try_translate_exceptions();
+        raise_from(PyExc_BufferError, "Error getting buffer");
+        return -1;
+    }
+    if (info == nullptr) {
+        pybind11_fail("FATAL UNEXPECTED SITUATION: tinfo->get_buffer() returned nullptr.");
+    }
+
     if ((flags & PyBUF_WRITABLE) == PyBUF_WRITABLE && info->readonly) {
         delete info;
         // view->obj = nullptr;  // Was just memset to 0, so not necessary

include/pybind11/detail/common.h

@@ -479,6 +479,8 @@ PYBIND11_WARNING_POP
         }
 
 \endrst */
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_CLANG("-Wgnu-zero-variadic-macro-arguments")
 #define PYBIND11_MODULE(name, variable, ...)                                                      \
     static ::pybind11::module_::module_def PYBIND11_CONCAT(pybind11_module_def_, name)            \
         PYBIND11_MAYBE_UNUSED;                                                                    \
@@ -499,6 +501,7 @@ PYBIND11_WARNING_POP
         PYBIND11_CATCH_INIT_EXCEPTIONS                                                            \
     }                                                                                             \
     void PYBIND11_CONCAT(pybind11_init_, name)(::pybind11::module_ & (variable))
+PYBIND11_WARNING_POP
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 

include/pybind11/detail/cpp_conduit.h

@@ -0,0 +1,77 @@
+// Copyright (c) 2024 The pybind Community.
+
+#pragma once
+
+#include <pybind11/pytypes.h>
+
+#include "common.h"
+#include "internals.h"
+
+#include <typeinfo>
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+// Forward declaration needed here: Refactoring opportunity.
+extern "C" inline PyObject *pybind11_object_new(PyTypeObject *type, PyObject *, PyObject *);
+
+inline bool type_is_managed_by_our_internals(PyTypeObject *type_obj) {
+#if defined(PYPY_VERSION)
+    auto &internals = get_internals();
+    return bool(internals.registered_types_py.find(type_obj)
+                != internals.registered_types_py.end());
+#else
+    return bool(type_obj->tp_new == pybind11_object_new);
+#endif
+}
+
+inline bool is_instance_method_of_type(PyTypeObject *type_obj, PyObject *attr_name) {
+    PyObject *descr = _PyType_Lookup(type_obj, attr_name);
+    return bool((descr != nullptr) && PyInstanceMethod_Check(descr));
+}
+
+inline object try_get_cpp_conduit_method(PyObject *obj) {
+    if (PyType_Check(obj)) {
+        return object();
+    }
+    PyTypeObject *type_obj = Py_TYPE(obj);
+    str attr_name("_pybind11_conduit_v1_");
+    bool assumed_to_be_callable = false;
+    if (type_is_managed_by_our_internals(type_obj)) {
+        if (!is_instance_method_of_type(type_obj, attr_name.ptr())) {
+            return object();
+        }
+        assumed_to_be_callable = true;
+    }
+    PyObject *method = PyObject_GetAttr(obj, attr_name.ptr());
+    if (method == nullptr) {
+        PyErr_Clear();
+        return object();
+    }
+    if (!assumed_to_be_callable && PyCallable_Check(method) == 0) {
+        Py_DECREF(method);
+        return object();
+    }
+    return reinterpret_steal<object>(method);
+}
+
+inline void *try_raw_pointer_ephemeral_from_cpp_conduit(handle src,
+                                                        const std::type_info *cpp_type_info) {
+    object method = try_get_cpp_conduit_method(src.ptr());
+    if (method) {
+        capsule cpp_type_info_capsule(const_cast<void *>(static_cast<const void *>(cpp_type_info)),
+                                      typeid(std::type_info).name());
+        object cpp_conduit = method(bytes(PYBIND11_PLATFORM_ABI_ID),
+                                    cpp_type_info_capsule,
+                                    bytes("raw_pointer_ephemeral"));
+        if (isinstance<capsule>(cpp_conduit)) {
+            return reinterpret_borrow<capsule>(cpp_conduit).get_pointer();
+        }
+    }
+    return nullptr;
+}
+
+#define PYBIND11_HAS_CPP_CONDUIT 1
+
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

include/pybind11/detail/exception_translation.h

@@ -0,0 +1,71 @@
+/*
+    pybind11/detail/exception_translation.h: means to translate C++ exceptions to Python exceptions
+
+    Copyright (c) 2024 The Pybind Development Team.
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "common.h"
+#include "internals.h"
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+// Apply all the extensions translators from a list
+// Return true if one of the translators completed without raising an exception
+// itself. Return of false indicates that if there are other translators
+// available, they should be tried.
+inline bool apply_exception_translators(std::forward_list<ExceptionTranslator> &translators) {
+    auto last_exception = std::current_exception();
+
+    for (auto &translator : translators) {
+        try {
+            translator(last_exception);
+            return true;
+        } catch (...) {
+            last_exception = std::current_exception();
+        }
+    }
+    return false;
+}
+
+inline void try_translate_exceptions() {
+    /* When an exception is caught, give each registered exception
+        translator a chance to translate it to a Python exception. First
+        all module-local translators will be tried in reverse order of
+        registration. If none of the module-locale translators handle
+        the exception (or there are no module-locale translators) then
+        the global translators will be tried, also in reverse order of
+        registration.
+
+        A translator may choose to do one of the following:
+
+        - catch the exception and call py::set_error()
+            to set a standard (or custom) Python exception, or
+        - do nothing and let the exception fall through to the next translator, or
+        - delegate translation to the next translator by throwing a new type of exception.
+        */
+
+    bool handled = with_exception_translators(
+        [&](std::forward_list<ExceptionTranslator> &exception_translators,
+            std::forward_list<ExceptionTranslator> &local_exception_translators) {
+            if (detail::apply_exception_translators(local_exception_translators)) {
+                return true;
+            }
+            if (detail::apply_exception_translators(exception_translators)) {
+                return true;
+            }
+            return false;
+        });
+
+    if (!handled) {
+        set_error(PyExc_SystemError, "Exception escaped from default exception translator!");
+    }
+}
+
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

include/pybind11/detail/internals.h

@@ -12,10 +12,10 @@
 #include "common.h"
 
 #if defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
-#    include "../gil.h"
+#    include <pybind11/gil.h>
 #endif
 
-#include "../pytypes.h"
+#include <pybind11/pytypes.h>
 
 #include <exception>
 #include <mutex>
@@ -39,7 +39,11 @@
 #    if PY_VERSION_HEX >= 0x030C0000 || defined(_MSC_VER)
 // Version bump for Python 3.12+, before first 3.12 beta release.
 // Version bump for MSVC piggy-backed on PR #4779. See comments there.
+#        ifdef Py_GIL_DISABLED
+#            define PYBIND11_INTERNALS_VERSION 6
+#        else
 #            define PYBIND11_INTERNALS_VERSION 5
+#        endif
 #    else
 #        define PYBIND11_INTERNALS_VERSION 4
 #    endif
@@ -177,6 +181,7 @@ static_assert(sizeof(instance_map_shard) % 64 == 0,
 struct internals {
 #ifdef Py_GIL_DISABLED
     pymutex mutex;
+    pymutex exception_translator_mutex;
 #endif
     // std::type_index -> pybind11's type information
     type_map<type_info *> registered_types_cpp;
@@ -321,15 +326,17 @@ struct type_info {
 #    define PYBIND11_INTERNALS_KIND ""
 #endif
 
+#define PYBIND11_PLATFORM_ABI_ID                                                                  \
+    PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB PYBIND11_BUILD_ABI             \
+        PYBIND11_BUILD_TYPE
+
 #define PYBIND11_INTERNALS_ID                                                                     \
     "__pybind11_internals_v" PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION)                        \
-        PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB                            \
-            PYBIND11_BUILD_ABI PYBIND11_BUILD_TYPE "__"
+        PYBIND11_PLATFORM_ABI_ID "__"
 
 #define PYBIND11_MODULE_LOCAL_ID                                                                  \
     "__pybind11_module_local_v" PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION)                     \
-        PYBIND11_INTERNALS_KIND PYBIND11_COMPILER_TYPE PYBIND11_STDLIB                            \
-            PYBIND11_BUILD_ABI PYBIND11_BUILD_TYPE "__"
+        PYBIND11_PLATFORM_ABI_ID "__"
 
 /// Each module locally stores a pointer to the `internals` data. The data
 /// itself is shared among modules with the same `PYBIND11_INTERNALS_ID`.
@@ -641,6 +648,19 @@ inline auto with_internals(const F &cb) -> decltype(cb(get_internals())) {
     return cb(internals);
 }
 
+template <typename F>
+inline auto with_exception_translators(const F &cb)
+    -> decltype(cb(get_internals().registered_exception_translators,
+                   get_local_internals().registered_exception_translators)) {
+    auto &internals = get_internals();
+#ifdef Py_GIL_DISABLED
+    std::unique_lock<pymutex> lock((internals).exception_translator_mutex);
+#endif
+    auto &local_internals = get_local_internals();
+    return cb(internals.registered_exception_translators,
+              local_internals.registered_exception_translators);
+}
+
 inline std::uint64_t mix64(std::uint64_t z) {
     // David Stafford's variant 13 of the MurmurHash3 finalizer popularized
     // by the SplitMix PRNG.

include/pybind11/detail/type_caster_base.h

@@ -9,16 +9,20 @@
 
 #pragma once
 
-#include "../pytypes.h"
+#include <pybind11/pytypes.h>
+
 #include "common.h"
+#include "cpp_conduit.h"
 #include "descr.h"
 #include "internals.h"
 #include "typeid.h"
 #include "value_and_holder.h"
 
 #include <cstdint>
+#include <cstring>
 #include <iterator>
 #include <new>
+#include <stdexcept>
 #include <string>
 #include <type_traits>
 #include <typeindex>
@@ -610,6 +614,13 @@ public:
         }
         return false;
     }
+    bool try_cpp_conduit(handle src) {
+        value = try_raw_pointer_ephemeral_from_cpp_conduit(src, cpptype);
+        if (value != nullptr) {
+            return true;
+        }
+        return false;
+    }
     void check_holder_compat() {}
 
     PYBIND11_NOINLINE static void *local_load(PyObject *src, const type_info *ti) {
@@ -741,6 +752,10 @@ public:
             return true;
         }
 
+        if (convert && cpptype && this_.try_cpp_conduit(src)) {
+            return true;
+        }
+
         return false;
     }
 
@@ -768,6 +783,32 @@ public:
     void *value = nullptr;
 };
 
+inline object cpp_conduit_method(handle self,
+                                 const bytes &pybind11_platform_abi_id,
+                                 const capsule &cpp_type_info_capsule,
+                                 const bytes &pointer_kind) {
+#ifdef PYBIND11_HAS_STRING_VIEW
+    using cpp_str = std::string_view;
+#else
+    using cpp_str = std::string;
+#endif
+    if (cpp_str(pybind11_platform_abi_id) != PYBIND11_PLATFORM_ABI_ID) {
+        return none();
+    }
+    if (std::strcmp(cpp_type_info_capsule.name(), typeid(std::type_info).name()) != 0) {
+        return none();
+    }
+    if (cpp_str(pointer_kind) != "raw_pointer_ephemeral") {
+        throw std::runtime_error("Invalid pointer_kind: \"" + std::string(pointer_kind) + "\"");
+    }
+    const auto *cpp_type_info = cpp_type_info_capsule.get_pointer<const std::type_info>();
+    type_caster_generic caster(*cpp_type_info);
+    if (!caster.load(self, false)) {
+        return none();
+    }
+    return capsule(caster.value, cpp_type_info->name());
+}
+
 /**
  * Determine suitable casting operator for pointer-or-lvalue-casting type casters.  The type caster
  * needs to provide `operator T*()` and `operator T&()` operators.

include/pybind11/eigen/matrix.h

@@ -9,7 +9,8 @@
 
 #pragma once
 
-#include "../numpy.h"
+#include <pybind11/numpy.h>
+
 #include "common.h"
 
 /* HINT: To suppress warnings originating from the Eigen headers, use -isystem.

include/pybind11/eigen/tensor.h

@@ -7,7 +7,8 @@
 
 #pragma once
 
-#include "../numpy.h"
+#include <pybind11/numpy.h>
+
 #include "common.h"
 
 #if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER)

include/pybind11/pybind11.h

@@ -9,8 +9,8 @@
 */
 
 #pragma once
-
 #include "detail/class.h"
+#include "detail/exception_translation.h"
 #include "detail/init.h"
 #include "attr.h"
 #include "gil.h"
@@ -95,24 +95,6 @@ inline std::string replace_newlines_and_squash(const char *text) {
     return result.substr(str_begin, str_range);
 }
 
-// Apply all the extensions translators from a list
-// Return true if one of the translators completed without raising an exception
-// itself. Return of false indicates that if there are other translators
-// available, they should be tried.
-inline bool apply_exception_translators(std::forward_list<ExceptionTranslator> &translators) {
-    auto last_exception = std::current_exception();
-
-    for (auto &translator : translators) {
-        try {
-            translator(last_exception);
-            return true;
-        } catch (...) {
-            last_exception = std::current_exception();
-        }
-    }
-    return false;
-}
-
 #if defined(_MSC_VER)
 #    define PYBIND11_COMPAT_STRDUP _strdup
 #else
@@ -610,7 +592,8 @@ protected:
         int index = 0;
         /* Create a nice pydoc rec including all signatures and
            docstrings of the functions in the overload chain */
-        if (chain && options::show_function_signatures()) {
+        if (chain && options::show_function_signatures()
+            && std::strcmp(rec->name, "_pybind11_conduit_v1_") != 0) {
             // First a generic signature
             signatures += rec->name;
             signatures += "(*args, **kwargs)\n";
@@ -619,7 +602,8 @@ protected:
         // Then specific overload signatures
         bool first_user_def = true;
         for (auto *it = chain_start; it != nullptr; it = it->next) {
-            if (options::show_function_signatures()) {
+            if (options::show_function_signatures()
+                && std::strcmp(rec->name, "_pybind11_conduit_v1_") != 0) {
                 if (index > 0) {
                     signatures += '\n';
                 }
@@ -1038,40 +1022,7 @@ protected:
             throw;
 #endif
         } catch (...) {
-            /* When an exception is caught, give each registered exception
-               translator a chance to translate it to a Python exception. First
-               all module-local translators will be tried in reverse order of
-               registration. If none of the module-locale translators handle
-               the exception (or there are no module-locale translators) then
-               the global translators will be tried, also in reverse order of
-               registration.
-
-               A translator may choose to do one of the following:
-
-                - catch the exception and call py::set_error()
-                  to set a standard (or custom) Python exception, or
-                - do nothing and let the exception fall through to the next translator, or
-                - delegate translation to the next translator by throwing a new type of exception.
-             */
-
-            bool handled = with_internals([&](internals &internals) {
-                auto &local_exception_translators
-                    = get_local_internals().registered_exception_translators;
-                if (detail::apply_exception_translators(local_exception_translators)) {
-                    return true;
-                }
-                auto &exception_translators = internals.registered_exception_translators;
-                if (detail::apply_exception_translators(exception_translators)) {
-                    return true;
-                }
-                return false;
-            });
-
-            if (handled) {
-                return nullptr;
-            }
-
-            set_error(PyExc_SystemError, "Exception escaped from default exception translator!");
+            try_translate_exceptions();
             return nullptr;
         }
 
@@ -1431,7 +1382,17 @@ protected:
             } else {
                 internals.registered_types_cpp[tindex] = tinfo;
             }
+
+            PYBIND11_WARNING_PUSH
+#if defined(__GNUC__) && __GNUC__ == 12
+            // When using GCC 12 these warnings are disabled as they trigger
+            // false positive warnings.  Discussed here:
+            // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115824.
+            PYBIND11_WARNING_DISABLE_GCC("-Warray-bounds")
+            PYBIND11_WARNING_DISABLE_GCC("-Wstringop-overread")
+#endif
             internals.registered_types_py[(PyTypeObject *) m_ptr] = {tinfo};
+            PYBIND11_WARNING_POP
         });
 
         if (rec.bases.size() > 1 || rec.multiple_inheritance) {
@@ -1652,6 +1613,7 @@ public:
                     = instances[std::type_index(typeid(type))];
             });
         }
+        def("_pybind11_conduit_v1_", cpp_conduit_method);
     }
 
     template <typename Base, detail::enable_if_t<is_base<Base>::value, int> = 0>
@@ -2624,9 +2586,11 @@ void implicitly_convertible() {
 }
 
 inline void register_exception_translator(ExceptionTranslator &&translator) {
-    detail::with_internals([&](detail::internals &internals) {
-        internals.registered_exception_translators.push_front(
-            std::forward<ExceptionTranslator>(translator));
+    detail::with_exception_translators(
+        [&](std::forward_list<ExceptionTranslator> &exception_translators,
+            std::forward_list<ExceptionTranslator> &local_exception_translators) {
+            (void) local_exception_translators;
+            exception_translators.push_front(std::forward<ExceptionTranslator>(translator));
         });
 }
 
@@ -2637,10 +2601,11 @@ inline void register_exception_translator(ExceptionTranslator &&translator) {
  * the exception.
  */
 inline void register_local_exception_translator(ExceptionTranslator &&translator) {
-    detail::with_internals([&](detail::internals &internals) {
-        (void) internals;
-        detail::get_local_internals().registered_exception_translators.push_front(
-            std::forward<ExceptionTranslator>(translator));
+    detail::with_exception_translators(
+        [&](std::forward_list<ExceptionTranslator> &exception_translators,
+            std::forward_list<ExceptionTranslator> &local_exception_translators) {
+            (void) exception_translators;
+            local_exception_translators.push_front(std::forward<ExceptionTranslator>(translator));
         });
 }
 

include/pybind11/pytypes.h

@@ -1259,6 +1259,7 @@ protected:
     using pointer = arrow_proxy<const handle>;
 
     sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) {}
+    sequence_fast_readonly() = default;
 
     // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
     reference dereference() const { return *ptr; }
@@ -1281,6 +1282,7 @@ protected:
     using pointer = arrow_proxy<const sequence_accessor>;
 
     sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) {}
+    sequence_slow_readwrite() = default;
 
     reference dereference() const { return {obj, static_cast<size_t>(index)}; }
     void increment() { ++index; }

include/pybind11/stl.h

@@ -11,11 +11,14 @@
 
 #include "pybind11.h"
 #include "detail/common.h"
+#include "detail/descr.h"
+#include "detail/type_caster_base.h"
 
 #include <deque>
 #include <initializer_list>
 #include <list>
 #include <map>
+#include <memory>
 #include <ostream>
 #include <set>
 #include <unordered_map>
@@ -349,39 +352,68 @@ struct type_caster<std::deque<Type, Alloc>> : list_caster<std::deque<Type, Alloc
 template <typename Type, typename Alloc>
 struct type_caster<std::list<Type, Alloc>> : list_caster<std::list<Type, Alloc>, Type> {};
 
+template <typename ArrayType, typename V, size_t... I>
+ArrayType vector_to_array_impl(V &&v, index_sequence<I...>) {
+    return {{std::move(v[I])...}};
+}
+
+// Based on https://en.cppreference.com/w/cpp/container/array/to_array
+template <typename ArrayType, size_t N, typename V>
+ArrayType vector_to_array(V &&v) {
+    return vector_to_array_impl<ArrayType, V>(std::forward<V>(v), make_index_sequence<N>{});
+}
+
 template <typename ArrayType, typename Value, bool Resizable, size_t Size = 0>
 struct array_caster {
     using value_conv = make_caster<Value>;
 
 private:
-    template <bool R = Resizable>
-    bool require_size(enable_if_t<R, size_t> size) {
-        if (value.size() != size) {
-            value.resize(size);
-        }
-        return true;
-    }
-    template <bool R = Resizable>
-    bool require_size(enable_if_t<!R, size_t> size) {
-        return size == Size;
-    }
+    std::unique_ptr<ArrayType> value;
 
+    template <bool R = Resizable, enable_if_t<R, int> = 0>
     bool convert_elements(handle seq, bool convert) {
         auto l = reinterpret_borrow<sequence>(seq);
-        if (!require_size(l.size())) {
-            return false;
-        }
+        value.reset(new ArrayType{});
+        // Using `resize` to preserve the behavior exactly as it was before PR #5305
+        // For the `resize` to work, `Value` must be default constructible.
+        // For `std::valarray`, this is a requirement:
+        // https://en.cppreference.com/w/cpp/named_req/NumericType
+        value->resize(l.size());
         size_t ctr = 0;
         for (const auto &it : l) {
             value_conv conv;
             if (!conv.load(it, convert)) {
                 return false;
             }
-            value[ctr++] = cast_op<Value &&>(std::move(conv));
+            (*value)[ctr++] = cast_op<Value &&>(std::move(conv));
         }
         return true;
     }
 
+    template <bool R = Resizable, enable_if_t<!R, int> = 0>
+    bool convert_elements(handle seq, bool convert) {
+        auto l = reinterpret_borrow<sequence>(seq);
+        if (l.size() != Size) {
+            return false;
+        }
+        // The `temp` storage is needed to support `Value` types that are not
+        // default-constructible.
+        // Deliberate choice: no template specializations, for simplicity, and
+        // because the compile time overhead for the specializations is deemed
+        // more significant than the runtime overhead for the `temp` storage.
+        std::vector<Value> temp;
+        temp.reserve(l.size());
+        for (auto it : l) {
+            value_conv conv;
+            if (!conv.load(it, convert)) {
+                return false;
+            }
+            temp.emplace_back(cast_op<Value &&>(std::move(conv)));
+        }
+        value.reset(new ArrayType(vector_to_array<ArrayType, Size>(std::move(temp))));
+        return true;
+    }
+
 public:
     bool load(handle src, bool convert) {
         if (!PyObjectTypeIsConvertibleToStdVector(src.ptr())) {
@@ -416,12 +448,36 @@ public:
         return l.release();
     }
 
-    PYBIND11_TYPE_CASTER(ArrayType,
-                         const_name<Resizable>(const_name(""), const_name("Annotated["))
-                             + const_name("list[") + value_conv::name + const_name("]")
-                             + const_name<Resizable>(const_name(""),
-                                                     const_name(", FixedSize(")
-                                                         + const_name<Size>() + const_name(")]")));
+    // Code copied from PYBIND11_TYPE_CASTER macro.
+    // Intentionally preserving the behavior exactly as it was before PR #5305
+    template <typename T_, enable_if_t<std::is_same<ArrayType, remove_cv_t<T_>>::value, int> = 0>
+    static handle cast(T_ *src, return_value_policy policy, handle parent) {
+        if (!src) {
+            return none().release();
+        }
+        if (policy == return_value_policy::take_ownership) {
+            auto h = cast(std::move(*src), policy, parent);
+            delete src; // WARNING: Assumes `src` was allocated with `new`.
+            return h;
+        }
+        return cast(*src, policy, parent);
+    }
+
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator ArrayType *() { return &(*value); }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator ArrayType &() { return *value; }
+    // NOLINTNEXTLINE(google-explicit-constructor)
+    operator ArrayType &&() && { return std::move(*value); }
+
+    template <typename T_>
+    using cast_op_type = movable_cast_op_type<T_>;
+
+    static constexpr auto name
+        = const_name<Resizable>(const_name(""), const_name("Annotated[")) + const_name("list[")
+          + value_conv::name + const_name("]")
+          + const_name<Resizable>(
+              const_name(""), const_name(", FixedSize(") + const_name<Size>() + const_name(")]"));
 };
 
 template <typename Type, size_t Size>

include/pybind11/stl/filesystem.h

@@ -4,11 +4,11 @@
 
 #pragma once
 
-#include "../pybind11.h"
-#include "../detail/common.h"
-#include "../detail/descr.h"
-#include "../cast.h"
-#include "../pytypes.h"
+#include <pybind11/cast.h>
+#include <pybind11/detail/common.h>
+#include <pybind11/detail/descr.h>
+#include <pybind11/pybind11.h>
+#include <pybind11/pytypes.h>
 
 #include <string>
 

include/pybind11/typing.h

@@ -100,9 +100,7 @@ class Never : public none {
     using none::none;
 };
 
-#if defined(__cpp_nontype_template_parameter_class)                                               \
-    && (/* See #5201 */ !defined(__GNUC__)                                                        \
-        || (__GNUC__ > 10 || (__GNUC__ == 10 && __GNUC_MINOR__ >= 3)))
+#if defined(__cpp_nontype_template_args) && __cpp_nontype_template_args >= 201911L
 #    define PYBIND11_TYPING_H_HAS_STRING_LITERAL
 template <size_t N>
 struct StringLiteral {

include/pybind11/warnings.h

@@ -0,0 +1,75 @@
+/*
+    pybind11/warnings.h: Python warnings wrappers.
+
+    Copyright (c) 2024 Jan Iwaszkiewicz <jiwaszkiewicz6@gmail.com>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+#include "detail/common.h"
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+inline bool PyWarning_Check(PyObject *obj) {
+    int result = PyObject_IsSubclass(obj, PyExc_Warning);
+    if (result == 1) {
+        return true;
+    }
+    if (result == -1) {
+        raise_from(PyExc_SystemError,
+                   "pybind11::detail::PyWarning_Check(): PyObject_IsSubclass() call failed.");
+        throw error_already_set();
+    }
+    return false;
+}
+
+PYBIND11_NAMESPACE_END(detail)
+
+PYBIND11_NAMESPACE_BEGIN(warnings)
+
+inline object
+new_warning_type(handle scope, const char *name, handle base = PyExc_RuntimeWarning) {
+    if (!detail::PyWarning_Check(base.ptr())) {
+        pybind11_fail("pybind11::warnings::new_warning_type(): cannot create custom warning, base "
+                      "must be a subclass of "
+                      "PyExc_Warning!");
+    }
+    if (hasattr(scope, name)) {
+        pybind11_fail("pybind11::warnings::new_warning_type(): an attribute with name \""
+                      + std::string(name) + "\" exists already.");
+    }
+    std::string full_name = scope.attr("__name__").cast<std::string>() + std::string(".") + name;
+    handle h(PyErr_NewException(full_name.c_str(), base.ptr(), nullptr));
+    if (!h) {
+        raise_from(PyExc_SystemError,
+                   "pybind11::warnings::new_warning_type(): PyErr_NewException() call failed.");
+        throw error_already_set();
+    }
+    auto obj = reinterpret_steal<object>(h);
+    scope.attr(name) = obj;
+    return obj;
+}
+
+// Similar to Python `warnings.warn()`
+inline void
+warn(const char *message, handle category = PyExc_RuntimeWarning, int stack_level = 2) {
+    if (!detail::PyWarning_Check(category.ptr())) {
+        pybind11_fail(
+            "pybind11::warnings::warn(): cannot raise warning, category must be a subclass of "
+            "PyExc_Warning!");
+    }
+
+    if (PyErr_WarnEx(category.ptr(), message, stack_level) == -1) {
+        throw error_already_set();
+    }
+}
+
+PYBIND11_NAMESPACE_END(warnings)
+
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

pybind11/__main__.py

@@ -2,13 +2,35 @@
 from __future__ import annotations
 
 import argparse
-import shlex
+import re
 import sys
 import sysconfig
 
 from ._version import __version__
 from .commands import get_cmake_dir, get_include, get_pkgconfig_dir
 
+# This is the conditional used for os.path being posixpath
+if "posix" in sys.builtin_module_names:
+    from shlex import quote
+elif "nt" in sys.builtin_module_names:
+    # See https://github.com/mesonbuild/meson/blob/db22551ed9d2dd7889abea01cc1c7bba02bf1c75/mesonbuild/utils/universal.py#L1092-L1121
+    # and the original documents:
+    # https://docs.microsoft.com/en-us/cpp/c-language/parsing-c-command-line-arguments and
+    # https://blogs.msdn.microsoft.com/twistylittlepassagesallalike/2011/04/23/everyone-quotes-command-line-arguments-the-wrong-way/
+    UNSAFE = re.compile("[ \t\n\r]")
+
+    def quote(s: str) -> str:
+        if s and not UNSAFE.search(s):
+            return s
+
+        # Paths cannot contain a '"' on Windows, so we don't need to worry
+        # about nuanced counting here.
+        return f'"{s}\\"' if s.endswith("\\") else f'"{s}"'
+else:
+
+    def quote(s: str) -> str:
+        return s
+
 
 def print_includes() -> None:
     dirs = [
@@ -23,7 +45,7 @@ def print_includes() -> None:
         if d and d not in unique_dirs:
             unique_dirs.append(d)
 
-    print(" ".join(shlex.quote(f"-I{d}") for d in unique_dirs))
+    print(" ".join(quote(f"-I{d}") for d in unique_dirs))
 
 
 def main() -> None:
@@ -55,9 +77,9 @@ def main() -> None:
     if args.includes:
         print_includes()
     if args.cmakedir:
-        print(shlex.quote(get_cmake_dir()))
+        print(quote(get_cmake_dir()))
     if args.pkgconfigdir:
-        print(shlex.quote(get_pkgconfig_dir()))
+        print(quote(get_pkgconfig_dir()))
 
 
 if __name__ == "__main__":

tests/CMakeLists.txt

@@ -5,16 +5,7 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 3.5)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 # Filter out items; print an optional message if any items filtered. This ignores extensions.
 #
@@ -76,8 +67,8 @@ project(pybind11_tests CXX)
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/../tools")
 
 option(PYBIND11_WERROR "Report all warnings as errors" OFF)
-option(DOWNLOAD_EIGEN "Download EIGEN (requires CMake 3.11+)" OFF)
-option(PYBIND11_CUDA_TESTS "Enable building CUDA tests (requires CMake 3.12+)" OFF)
+option(DOWNLOAD_EIGEN "Download EIGEN" OFF)
+option(PYBIND11_CUDA_TESTS "Enable building CUDA tests" OFF)
 set(PYBIND11_TEST_OVERRIDE
     ""
     CACHE STRING "Tests from ;-separated list of *.cpp files will be built instead of all tests")
@@ -127,6 +118,7 @@ set(PYBIND11_TEST_FILES
     test_const_name
     test_constants_and_functions
     test_copy_move
+    test_cpp_conduit
     test_custom_type_casters
     test_custom_type_setup
     test_docstring_options
@@ -163,7 +155,8 @@ set(PYBIND11_TEST_FILES
     test_unnamed_namespace_a
     test_unnamed_namespace_b
     test_vector_unique_ptr_member
-    test_virtual_functions)
+    test_virtual_functions
+    test_warnings)
 
 # Invoking cmake with something like:
 #     cmake -DPYBIND11_TEST_OVERRIDE="test_callbacks.cpp;test_pickling.cpp" ..
@@ -226,6 +219,8 @@ tests_extra_targets("test_exceptions.py;test_local_bindings.py;test_stl.py;test_
 # And add additional targets for other tests.
 tests_extra_targets("test_exceptions.py" "cross_module_interleaved_error_already_set")
 tests_extra_targets("test_gil_scoped.py" "cross_module_gil_utils")
+tests_extra_targets("test_cpp_conduit.py"
+                    "exo_planet_pybind11;exo_planet_c_api;home_planet_very_lonely_traveler")
 
 set(PYBIND11_EIGEN_REPO
     "https://gitlab.com/libeigen/eigen.git"
@@ -249,25 +244,21 @@ endif()
 if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
   # Try loading via newer Eigen's Eigen3Config first (bypassing tools/FindEigen3.cmake).
   # Eigen 3.3.1+ exports a cmake 3.0+ target for handling dependency requirements, but also
-  # produces a fatal error if loaded from a pre-3.0 cmake.
   if(DOWNLOAD_EIGEN)
-    if(CMAKE_VERSION VERSION_LESS 3.11)
-      message(FATAL_ERROR "CMake 3.11+ required when using DOWNLOAD_EIGEN")
+    if(CMAKE_VERSION VERSION_LESS 3.18)
+      set(_opts)
+    else()
+      set(_opts SOURCE_SUBDIR no-cmake-build)
     endif()
-
     include(FetchContent)
     FetchContent_Declare(
       eigen
       GIT_REPOSITORY "${PYBIND11_EIGEN_REPO}"
-      GIT_TAG "${PYBIND11_EIGEN_VERSION_HASH}")
-
-    FetchContent_GetProperties(eigen)
-    if(NOT eigen_POPULATED)
-      message(
-        STATUS
-          "Downloading Eigen ${PYBIND11_EIGEN_VERSION_STRING} (${PYBIND11_EIGEN_VERSION_HASH}) from ${PYBIND11_EIGEN_REPO}"
-      )
-      FetchContent_Populate(eigen)
+      GIT_TAG "${PYBIND11_EIGEN_VERSION_HASH}"
+      ${_opts})
+    FetchContent_MakeAvailable(eigen)
+    if(NOT CMAKE_VERSION VERSION_LESS 3.18)
+      set(EIGEN3_INCLUDE_DIR "${eigen_SOURCE_DIR}")
     endif()
 
     set(EIGEN3_INCLUDE_DIR ${eigen_SOURCE_DIR})
@@ -315,8 +306,7 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
       list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
     endif()
-    message(
-      STATUS "Building tests WITHOUT Eigen, use -DDOWNLOAD_EIGEN=ON on CMake 3.11+ to download")
+    message(STATUS "Building tests WITHOUT Eigen, use -DDOWNLOAD_EIGEN=ON to download")
   endif()
 endif()
 
@@ -396,6 +386,9 @@ function(pybind11_enable_warnings target_name)
               -Wdeprecated
               -Wundef
               -Wnon-virtual-dtor)
+    if(DEFINED CMAKE_CXX_STANDARD AND NOT CMAKE_CXX_STANDARD VERSION_LESS 20)
+      target_compile_options(${target_name} PRIVATE -Wpedantic)
+    endif()
   endif()
 
   if(PYBIND11_WERROR)
@@ -501,12 +494,10 @@ foreach(target ${test_targets})
 endforeach()
 
 # Provide nice organisation in IDEs
-if(NOT CMAKE_VERSION VERSION_LESS 3.8)
 source_group(
   TREE "${CMAKE_CURRENT_SOURCE_DIR}/../include"
   PREFIX "Header Files"
   FILES ${PYBIND11_HEADERS})
-endif()
 
 # Make sure pytest is found or produce a warning
 pybind11_find_import(pytest VERSION 3.1)

tests/conftest.py

@@ -136,7 +136,7 @@ class Capture:
         return Output(self.err)
 
 
-@pytest.fixture()
+@pytest.fixture
 def capture(capsys):
     """Extended `capsys` with context manager and custom equality operators"""
     return Capture(capsys)
@@ -172,7 +172,7 @@ def _sanitize_docstring(thing):
     return _sanitize_general(s)
 
 
-@pytest.fixture()
+@pytest.fixture
 def doc():
     """Sanitize docstrings and add custom failure explanation"""
     return SanitizedString(_sanitize_docstring)
@@ -184,7 +184,7 @@ def _sanitize_message(thing):
     return _hexadecimal.sub("0", s)
 
 
-@pytest.fixture()
+@pytest.fixture
 def msg():
     """Sanitize messages and add custom failure explanation"""
     return SanitizedString(_sanitize_message)

tests/custom_exceptions.py

@@ -0,0 +1,10 @@
+from __future__ import annotations
+
+
+class PythonMyException7(Exception):
+    def __init__(self, message):
+        self.message = message
+        super().__init__(message)
+
+    def __str__(self):
+        return "[PythonMyException7]: " + self.message.a

tests/exo_planet_c_api.cpp

@@ -0,0 +1,103 @@
+// Copyright (c) 2024 The pybind Community.
+
+// THIS MUST STAY AT THE TOP!
+#include <pybind11/pybind11.h> // EXCLUSIVELY for PYBIND11_PLATFORM_ABI_ID
+// Potential future direction to maximize reusability:
+// (e.g. for use from SWIG, Cython, PyCLIF, nanobind):
+//     #include <pybind11/compat/platform_abi_id.h>
+// This would only depend on:
+//     1. A C++ compiler, WITHOUT requiring -fexceptions.
+//     2. Python.h
+
+#include "test_cpp_conduit_traveler_types.h"
+
+#include <Python.h>
+#include <typeinfo>
+
+namespace {
+
+void *get_cpp_conduit_void_ptr(PyObject *py_obj, const std::type_info *cpp_type_info) {
+    PyObject *cpp_type_info_capsule
+        = PyCapsule_New(const_cast<void *>(static_cast<const void *>(cpp_type_info)),
+                        typeid(std::type_info).name(),
+                        nullptr);
+    if (cpp_type_info_capsule == nullptr) {
+        return nullptr;
+    }
+    PyObject *cpp_conduit = PyObject_CallMethod(py_obj,
+                                                "_pybind11_conduit_v1_",
+                                                "yOy",
+                                                PYBIND11_PLATFORM_ABI_ID,
+                                                cpp_type_info_capsule,
+                                                "raw_pointer_ephemeral");
+    Py_DECREF(cpp_type_info_capsule);
+    if (cpp_conduit == nullptr) {
+        return nullptr;
+    }
+    void *void_ptr = PyCapsule_GetPointer(cpp_conduit, cpp_type_info->name());
+    Py_DECREF(cpp_conduit);
+    if (PyErr_Occurred()) {
+        return nullptr;
+    }
+    return void_ptr;
+}
+
+template <typename T>
+T *get_cpp_conduit_type_ptr(PyObject *py_obj) {
+    void *void_ptr = get_cpp_conduit_void_ptr(py_obj, &typeid(T));
+    if (void_ptr == nullptr) {
+        return nullptr;
+    }
+    return static_cast<T *>(void_ptr);
+}
+
+extern "C" PyObject *wrapGetLuggage(PyObject * /*self*/, PyObject *traveler) {
+    const auto *cpp_traveler
+        = get_cpp_conduit_type_ptr<pybind11_tests::test_cpp_conduit::Traveler>(traveler);
+    if (cpp_traveler == nullptr) {
+        return nullptr;
+    }
+    return PyUnicode_FromString(cpp_traveler->luggage.c_str());
+}
+
+extern "C" PyObject *wrapGetPoints(PyObject * /*self*/, PyObject *premium_traveler) {
+    const auto *cpp_premium_traveler
+        = get_cpp_conduit_type_ptr<pybind11_tests::test_cpp_conduit::PremiumTraveler>(
+            premium_traveler);
+    if (cpp_premium_traveler == nullptr) {
+        return nullptr;
+    }
+    return PyLong_FromLong(static_cast<long>(cpp_premium_traveler->points));
+}
+
+PyMethodDef ThisMethodDef[] = {{"GetLuggage", wrapGetLuggage, METH_O, nullptr},
+                               {"GetPoints", wrapGetPoints, METH_O, nullptr},
+                               {nullptr, nullptr, 0, nullptr}};
+
+struct PyModuleDef ThisModuleDef = {
+    PyModuleDef_HEAD_INIT, // m_base
+    "exo_planet_c_api",    // m_name
+    nullptr,               // m_doc
+    -1,                    // m_size
+    ThisMethodDef,         // m_methods
+    nullptr,               // m_slots
+    nullptr,               // m_traverse
+    nullptr,               // m_clear
+    nullptr                // m_free
+};
+
+} // namespace
+
+#if defined(WIN32) || defined(_WIN32)
+#    define EXO_PLANET_C_API_EXPORT __declspec(dllexport)
+#else
+#    define EXO_PLANET_C_API_EXPORT __attribute__((visibility("default")))
+#endif
+
+extern "C" EXO_PLANET_C_API_EXPORT PyObject *PyInit_exo_planet_c_api() {
+    PyObject *m = PyModule_Create(&ThisModuleDef);
+    if (m == nullptr) {
+        return nullptr;
+    }
+    return m;
+}

tests/exo_planet_pybind11.cpp

@@ -0,0 +1,19 @@
+// Copyright (c) 2024 The pybind Community.
+
+#if defined(PYBIND11_INTERNALS_VERSION)
+#    undef PYBIND11_INTERNALS_VERSION
+#endif
+#define PYBIND11_INTERNALS_VERSION 900000001
+
+#include "test_cpp_conduit_traveler_bindings.h"
+
+namespace pybind11_tests {
+namespace test_cpp_conduit {
+
+PYBIND11_MODULE(exo_planet_pybind11, m) {
+    wrap_traveler(m);
+    m.def("wrap_very_lonely_traveler", [m]() { wrap_very_lonely_traveler(m); });
+}
+
+} // namespace test_cpp_conduit
+} // namespace pybind11_tests

tests/extra_python_package/test_files.py

@@ -9,7 +9,6 @@ import tarfile
 import zipfile
 
 # These tests must be run explicitly
-# They require CMake 3.15+ (--install)
 
 DIR = os.path.abspath(os.path.dirname(__file__))
 MAIN_DIR = os.path.dirname(os.path.dirname(DIR))
@@ -48,17 +47,20 @@ main_headers = {
     "include/pybind11/stl_bind.h",
     "include/pybind11/type_caster_pyobject_ptr.h",
     "include/pybind11/typing.h",
+    "include/pybind11/warnings.h",
 }
 
 detail_headers = {
     "include/pybind11/detail/class.h",
     "include/pybind11/detail/common.h",
+    "include/pybind11/detail/cpp_conduit.h",
     "include/pybind11/detail/descr.h",
     "include/pybind11/detail/init.h",
     "include/pybind11/detail/internals.h",
     "include/pybind11/detail/type_caster_base.h",
     "include/pybind11/detail/typeid.h",
     "include/pybind11/detail/value_and_holder.h",
+    "include/pybind11/detail/exception_translation.h",
 }
 
 eigen_headers = {

tests/home_planet_very_lonely_traveler.cpp

@@ -0,0 +1,13 @@
+// Copyright (c) 2024 The pybind Community.
+
+#include "test_cpp_conduit_traveler_bindings.h"
+
+namespace pybind11_tests {
+namespace test_cpp_conduit {
+
+PYBIND11_MODULE(home_planet_very_lonely_traveler, m) {
+    m.def("wrap_very_lonely_traveler", [m]() { wrap_very_lonely_traveler(m); });
+}
+
+} // namespace test_cpp_conduit
+} // namespace pybind11_tests

tests/local_bindings.h

@@ -56,13 +56,13 @@ private:
     std::string message = "";
 };
 
-PYBIND11_MAKE_OPAQUE(LocalVec);
-PYBIND11_MAKE_OPAQUE(LocalVec2);
-PYBIND11_MAKE_OPAQUE(LocalMap);
-PYBIND11_MAKE_OPAQUE(NonLocalVec);
-// PYBIND11_MAKE_OPAQUE(NonLocalVec2); // same type as LocalVec2
-PYBIND11_MAKE_OPAQUE(NonLocalMap);
-PYBIND11_MAKE_OPAQUE(NonLocalMap2);
+PYBIND11_MAKE_OPAQUE(LocalVec)
+PYBIND11_MAKE_OPAQUE(LocalVec2)
+PYBIND11_MAKE_OPAQUE(LocalMap)
+PYBIND11_MAKE_OPAQUE(NonLocalVec)
+// PYBIND11_MAKE_OPAQUE(NonLocalVec2) // same type as LocalVec2
+PYBIND11_MAKE_OPAQUE(NonLocalMap)
+PYBIND11_MAKE_OPAQUE(NonLocalMap2)
 
 // Simple bindings (used with the above):
 template <typename T, int Adjust = 0, typename... Args>
@@ -70,7 +70,7 @@ py::class_<T> bind_local(Args &&...args) {
     return py::class_<T>(std::forward<Args>(args)...).def(py::init<int>()).def("get", [](T &i) {
         return i.i + Adjust;
     });
-};
+}
 
 // Simulate a foreign library base class (to match the example in the docs):
 namespace pets {

tests/pyproject.toml

@@ -10,10 +10,6 @@ name = "pybind11_tests"
 version = "0.0.1"
 dependencies = ["pytest", "pytest-timeout", "numpy", "scipy"]
 
-[tool.scikit-build]
-# Hide a warning while we also support CMake < 3.15
-cmake.version = ">=3.15"
-
 [tool.scikit-build.cmake.define]
 PYBIND11_FINDPYTHON = true
 

tests/test_async.py

@@ -11,7 +11,7 @@ if sys.platform.startswith("emscripten"):
     pytest.skip("Can't run a new event_loop in pyodide", allow_module_level=True)
 
 
-@pytest.fixture()
+@pytest.fixture
 def event_loop():
     loop = asyncio.new_event_loop()
     yield loop

tests/test_buffers.cpp

@@ -167,6 +167,18 @@ TEST_SUBMODULE(buffers, m) {
                  sizeof(float)});
         });
 
+    class BrokenMatrix : public Matrix {
+    public:
+        BrokenMatrix(py::ssize_t rows, py::ssize_t cols) : Matrix(rows, cols) {}
+        void throw_runtime_error() { throw std::runtime_error("See PR #5324 for context."); }
+    };
+    py::class_<BrokenMatrix>(m, "BrokenMatrix", py::buffer_protocol())
+        .def(py::init<py::ssize_t, py::ssize_t>())
+        .def_buffer([](BrokenMatrix &m) {
+            m.throw_runtime_error();
+            return py::buffer_info();
+        });
+
     // test_inherited_protocol
     class SquareMatrix : public Matrix {
     public:

tests/test_buffers.py

@@ -228,3 +228,10 @@ def test_buffer_docstring():
         m.get_buffer_info.__doc__.strip()
         == "get_buffer_info(arg0: Buffer) -> pybind11_tests.buffers.buffer_info"
     )
+
+
+def test_buffer_exception():
+    with pytest.raises(BufferError, match="Error getting buffer") as excinfo:
+        memoryview(m.BrokenMatrix(1, 1))
+    assert isinstance(excinfo.value.__cause__, RuntimeError)
+    assert "for context" in str(excinfo.value.__cause__)

tests/test_callbacks.cpp

@@ -148,7 +148,7 @@ TEST_SUBMODULE(callbacks, m) {
     m.def("dummy_function2", [](int i, int j) { return i + j; });
     m.def(
         "roundtrip",
-        [](std::function<int(int)> f, bool expect_none = false) {
+        [](std::function<int(int)> f, bool expect_none) {
             if (expect_none && f) {
                 throw std::runtime_error("Expected None to be converted to empty std::function");
             }

tests/test_class.py

@@ -149,6 +149,10 @@ def test_qualname(doc):
     assert m.NestBase.__module__ == "pybind11_tests.class_"
     assert m.NestBase.Nested.__module__ == "pybind11_tests.class_"
 
+    assert m.Pet.__module__ == "pybind11_tests.class_"
+    assert m.Pet.__qualname__ == "Pet"
+    assert m.Pet.name.__qualname__ == "Pet.name"
+
 
 def test_inheritance(msg):
     roger = m.Rabbit("Rabbit")

tests/test_cmake_build/installed_embed/CMakeLists.txt

@@ -1,13 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 project(test_installed_embed CXX)
 

tests/test_cmake_build/installed_function/CMakeLists.txt

@@ -1,14 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
-project(test_installed_module CXX)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 project(test_installed_function CXX)
 

tests/test_cmake_build/installed_target/CMakeLists.txt

@@ -1,13 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 project(test_installed_target CXX)
 

tests/test_cmake_build/subdirectory_embed/CMakeLists.txt

@@ -1,13 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 project(test_subdirectory_embed CXX)
 

tests/test_cmake_build/subdirectory_function/CMakeLists.txt

@@ -1,13 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 project(test_subdirectory_function CXX)
 

tests/test_cmake_build/subdirectory_target/CMakeLists.txt

@@ -1,13 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
-
-# The `cmake_minimum_required(VERSION 3.5...3.29)` syntax does not work with
-# some versions of VS that have a patched CMake 3.11. This forces us to emulate
-# the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.29)
-  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
-else()
-  cmake_policy(VERSION 3.29)
-endif()
+cmake_minimum_required(VERSION 3.15...3.30)
 
 project(test_subdirectory_target CXX)
 

tests/test_cpp_conduit.cpp

@@ -0,0 +1,22 @@
+// Copyright (c) 2024 The pybind Community.
+
+#include "pybind11_tests.h"
+#include "test_cpp_conduit_traveler_bindings.h"
+
+#include <typeinfo>
+
+namespace pybind11_tests {
+namespace test_cpp_conduit {
+
+TEST_SUBMODULE(cpp_conduit, m) {
+    m.attr("PYBIND11_PLATFORM_ABI_ID") = py::bytes(PYBIND11_PLATFORM_ABI_ID);
+    m.attr("cpp_type_info_capsule_Traveler")
+        = py::capsule(&typeid(Traveler), typeid(std::type_info).name());
+    m.attr("cpp_type_info_capsule_int") = py::capsule(&typeid(int), typeid(std::type_info).name());
+
+    wrap_traveler(m);
+    wrap_lonely_traveler(m);
+}
+
+} // namespace test_cpp_conduit
+} // namespace pybind11_tests

tests/test_cpp_conduit.py

@@ -0,0 +1,162 @@
+# Copyright (c) 2024 The pybind Community.
+
+from __future__ import annotations
+
+import exo_planet_c_api
+import exo_planet_pybind11
+import home_planet_very_lonely_traveler
+import pytest
+
+from pybind11_tests import cpp_conduit as home_planet
+
+
+def test_traveler_getattr_actually_exists():
+    t_h = home_planet.Traveler("home")
+    assert t_h.any_name == "Traveler GetAttr: any_name luggage: home"
+
+
+def test_premium_traveler_getattr_actually_exists():
+    t_h = home_planet.PremiumTraveler("home", 7)
+    assert t_h.secret_name == "PremiumTraveler GetAttr: secret_name points: 7"
+
+
+def test_call_cpp_conduit_success():
+    t_h = home_planet.Traveler("home")
+    cap = t_h._pybind11_conduit_v1_(
+        home_planet.PYBIND11_PLATFORM_ABI_ID,
+        home_planet.cpp_type_info_capsule_Traveler,
+        b"raw_pointer_ephemeral",
+    )
+    assert cap.__class__.__name__ == "PyCapsule"
+
+
+def test_call_cpp_conduit_platform_abi_id_mismatch():
+    t_h = home_planet.Traveler("home")
+    cap = t_h._pybind11_conduit_v1_(
+        home_planet.PYBIND11_PLATFORM_ABI_ID + b"MISMATCH",
+        home_planet.cpp_type_info_capsule_Traveler,
+        b"raw_pointer_ephemeral",
+    )
+    assert cap is None
+
+
+def test_call_cpp_conduit_cpp_type_info_capsule_mismatch():
+    t_h = home_planet.Traveler("home")
+    cap = t_h._pybind11_conduit_v1_(
+        home_planet.PYBIND11_PLATFORM_ABI_ID,
+        home_planet.cpp_type_info_capsule_int,
+        b"raw_pointer_ephemeral",
+    )
+    assert cap is None
+
+
+def test_call_cpp_conduit_pointer_kind_invalid():
+    t_h = home_planet.Traveler("home")
+    with pytest.raises(
+        RuntimeError, match='^Invalid pointer_kind: "raw_pointer_ephemreal"$'
+    ):
+        t_h._pybind11_conduit_v1_(
+            home_planet.PYBIND11_PLATFORM_ABI_ID,
+            home_planet.cpp_type_info_capsule_Traveler,
+            b"raw_pointer_ephemreal",
+        )
+
+
+def test_home_only_basic():
+    t_h = home_planet.Traveler("home")
+    assert t_h.luggage == "home"
+    assert home_planet.get_luggage(t_h) == "home"
+
+
+def test_home_only_premium():
+    p_h = home_planet.PremiumTraveler("home", 2)
+    assert p_h.luggage == "home"
+    assert home_planet.get_luggage(p_h) == "home"
+    assert home_planet.get_points(p_h) == 2
+
+
+def test_exo_only_basic():
+    t_e = exo_planet_pybind11.Traveler("exo")
+    assert t_e.luggage == "exo"
+    assert exo_planet_pybind11.get_luggage(t_e) == "exo"
+
+
+def test_exo_only_premium():
+    p_e = exo_planet_pybind11.PremiumTraveler("exo", 3)
+    assert p_e.luggage == "exo"
+    assert exo_planet_pybind11.get_luggage(p_e) == "exo"
+    assert exo_planet_pybind11.get_points(p_e) == 3
+
+
+def test_home_passed_to_exo_basic():
+    t_h = home_planet.Traveler("home")
+    assert exo_planet_pybind11.get_luggage(t_h) == "home"
+
+
+def test_exo_passed_to_home_basic():
+    t_e = exo_planet_pybind11.Traveler("exo")
+    assert home_planet.get_luggage(t_e) == "exo"
+
+
+def test_home_passed_to_exo_premium():
+    p_h = home_planet.PremiumTraveler("home", 2)
+    assert exo_planet_pybind11.get_luggage(p_h) == "home"
+    assert exo_planet_pybind11.get_points(p_h) == 2
+
+
+def test_exo_passed_to_home_premium():
+    p_e = exo_planet_pybind11.PremiumTraveler("exo", 3)
+    assert home_planet.get_luggage(p_e) == "exo"
+    assert home_planet.get_points(p_e) == 3
+
+
+@pytest.mark.parametrize(
+    "traveler_type", [home_planet.Traveler, exo_planet_pybind11.Traveler]
+)
+def test_exo_planet_c_api_traveler(traveler_type):
+    t = traveler_type("socks")
+    assert exo_planet_c_api.GetLuggage(t) == "socks"
+
+
+@pytest.mark.parametrize(
+    "premium_traveler_type",
+    [home_planet.PremiumTraveler, exo_planet_pybind11.PremiumTraveler],
+)
+def test_exo_planet_c_api_premium_traveler(premium_traveler_type):
+    pt = premium_traveler_type("gucci", 5)
+    assert exo_planet_c_api.GetLuggage(pt) == "gucci"
+    assert exo_planet_c_api.GetPoints(pt) == 5
+
+
+def test_home_planet_wrap_very_lonely_traveler():
+    # This does not exercise the cpp_conduit feature, but is here to
+    # demonstrate that the cpp_conduit feature does not solve all
+    # cross-extension interoperability issues.
+    # Here is the proof that the following works for extensions with
+    # matching `PYBIND11_INTERNALS_ID`s:
+    #     test_cpp_conduit.cpp:
+    #         py::class_<LonelyTraveler>
+    #     home_planet_very_lonely_traveler.cpp:
+    #         py::class_<VeryLonelyTraveler, LonelyTraveler>
+    # See test_exo_planet_pybind11_wrap_very_lonely_traveler() for the negative
+    # test.
+    assert home_planet.LonelyTraveler is not None  # Verify that the base class exists.
+    home_planet_very_lonely_traveler.wrap_very_lonely_traveler()
+    # Ensure that the derived class exists.
+    assert home_planet_very_lonely_traveler.VeryLonelyTraveler is not None
+
+
+def test_exo_planet_pybind11_wrap_very_lonely_traveler():
+    # See comment under test_home_planet_wrap_very_lonely_traveler() first.
+    # Here the `PYBIND11_INTERNALS_ID`s don't match between:
+    #     test_cpp_conduit.cpp:
+    #         py::class_<LonelyTraveler>
+    #     exo_planet_pybind11.cpp:
+    #         py::class_<VeryLonelyTraveler, LonelyTraveler>
+    assert home_planet.LonelyTraveler is not None  # Verify that the base class exists.
+    with pytest.raises(
+        RuntimeError,
+        match='^generic_type: type "VeryLonelyTraveler" referenced unknown base type '
+        '"pybind11_tests::test_cpp_conduit::LonelyTraveler"$',
+    ):
+        exo_planet_pybind11.wrap_very_lonely_traveler()

tests/test_cpp_conduit_traveler_bindings.h

@@ -0,0 +1,47 @@
+// Copyright (c) 2024 The pybind Community.
+
+#pragma once
+
+#include <pybind11/pybind11.h>
+
+#include "test_cpp_conduit_traveler_types.h"
+
+#include <string>
+
+namespace pybind11_tests {
+namespace test_cpp_conduit {
+
+namespace py = pybind11;
+
+inline void wrap_traveler(py::module_ m) {
+    py::class_<Traveler>(m, "Traveler")
+        .def(py::init<std::string>())
+        .def_readwrite("luggage", &Traveler::luggage)
+        // See issue #3788:
+        .def("__getattr__", [](const Traveler &self, const std::string &key) {
+            return "Traveler GetAttr: " + key + " luggage: " + self.luggage;
+        });
+
+    m.def("get_luggage", [](const Traveler &person) { return person.luggage; });
+
+    py::class_<PremiumTraveler, Traveler>(m, "PremiumTraveler")
+        .def(py::init<std::string, int>())
+        .def_readwrite("points", &PremiumTraveler::points)
+        // See issue #3788:
+        .def("__getattr__", [](const PremiumTraveler &self, const std::string &key) {
+            return "PremiumTraveler GetAttr: " + key + " points: " + std::to_string(self.points);
+        });
+
+    m.def("get_points", [](const PremiumTraveler &person) { return person.points; });
+}
+
+inline void wrap_lonely_traveler(py::module_ m) {
+    py::class_<LonelyTraveler>(std::move(m), "LonelyTraveler");
+}
+
+inline void wrap_very_lonely_traveler(py::module_ m) {
+    py::class_<VeryLonelyTraveler, LonelyTraveler>(std::move(m), "VeryLonelyTraveler");
+}
+
+} // namespace test_cpp_conduit
+} // namespace pybind11_tests

tests/test_cpp_conduit_traveler_types.h

@@ -0,0 +1,25 @@
+// Copyright (c) 2024 The pybind Community.
+
+#pragma once
+
+#include <string>
+
+namespace pybind11_tests {
+namespace test_cpp_conduit {
+
+struct Traveler {
+    explicit Traveler(const std::string &luggage) : luggage(luggage) {}
+    std::string luggage;
+};
+
+struct PremiumTraveler : Traveler {
+    explicit PremiumTraveler(const std::string &luggage, int points)
+        : Traveler(luggage), points(points) {}
+    int points;
+};
+
+struct LonelyTraveler {};
+struct VeryLonelyTraveler : LonelyTraveler {};
+
+} // namespace test_cpp_conduit
+} // namespace pybind11_tests

tests/test_custom_type_setup.py

@@ -9,7 +9,7 @@ import env  # noqa: F401
 from pybind11_tests import custom_type_setup as m
 
 
-@pytest.fixture()
+@pytest.fixture
 def gc_tester():
     """Tests that an object is garbage collected.
 

tests/test_eigen_matrix.cpp

@@ -55,7 +55,7 @@ void reset_refs() {
 }
 
 // Returns element 2,1 from a matrix (used to test copy/nocopy)
-double get_elem(const Eigen::Ref<const Eigen::MatrixXd> &m) { return m(2, 1); };
+double get_elem(const Eigen::Ref<const Eigen::MatrixXd> &m) { return m(2, 1); }
 
 // Returns a matrix with 10*r + 100*c added to each matrix element (to help test that the matrix
 // reference is referencing rows/columns correctly).
@@ -76,7 +76,7 @@ struct CustomOperatorNew {
     Eigen::Matrix4d a = Eigen::Matrix4d::Zero();
     Eigen::Matrix4d b = Eigen::Matrix4d::Identity();
 
-    EIGEN_MAKE_ALIGNED_OPERATOR_NEW;
+    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
 };
 
 TEST_SUBMODULE(eigen_matrix, m) {

tests/test_exceptions.cpp

@@ -111,6 +111,16 @@ struct PythonAlreadySetInDestructor {
     py::str s;
 };
 
+struct CustomData {
+    explicit CustomData(const std::string &a) : a(a) {}
+    std::string a;
+};
+
+struct MyException7 {
+    explicit MyException7(const CustomData &message) : message(message) {}
+    CustomData message;
+};
+
 TEST_SUBMODULE(exceptions, m) {
     m.def("throw_std_exception",
           []() { throw std::runtime_error("This exception was intentionally thrown."); });
@@ -385,4 +395,33 @@ TEST_SUBMODULE(exceptions, m) {
 
     // m.def("pass_exception_void", [](const py::exception<void>&) {}); // Does not compile.
     m.def("return_exception_void", []() { return py::exception<void>(); });
+
+    m.def("throws7", []() {
+        auto data = CustomData("abc");
+        throw MyException7(data);
+    });
+
+    py::class_<CustomData>(m, "CustomData", py::module_local())
+        .def(py::init<const std::string &>())
+        .def_readwrite("a", &CustomData::a);
+
+    PYBIND11_CONSTINIT static py::gil_safe_call_once_and_store<py::object>
+        PythonMyException7_storage;
+    PythonMyException7_storage.call_once_and_store_result([&]() {
+        auto mod = py::module_::import("custom_exceptions");
+        py::object obj = mod.attr("PythonMyException7");
+        return obj;
+    });
+
+    py::register_local_exception_translator([](std::exception_ptr p) {
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const MyException7 &e) {
+            auto exc_type = PythonMyException7_storage.get_stored();
+            py::object exc_inst = exc_type(e.message);
+            PyErr_SetObject(PyExc_Exception, exc_inst.ptr());
+        }
+    });
 }

tests/test_exceptions.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 import sys
 
 import pytest
+from custom_exceptions import PythonMyException7
 
 import env
 import pybind11_cross_module_tests as cm
@@ -195,6 +196,10 @@ def test_custom(msg):
             raise RuntimeError("Exception error: caught child from parent") from err
     assert msg(excinfo.value) == "this is a helper-defined translated exception"
 
+    with pytest.raises(PythonMyException7) as excinfo:
+        m.throws7()
+    assert msg(excinfo.value) == "[PythonMyException7]: abc"
+
 
 def test_nested_throws(capture):
     """Tests nested (e.g. C++ -> Python -> C++) exception handling"""

tests/test_numpy_array.py

@@ -24,7 +24,7 @@ def test_dtypes():
             )
 
 
-@pytest.fixture()
+@pytest.fixture
 def arr():
     return np.array([[1, 2, 3], [4, 5, 6]], "=u2")
 

tests/test_opaque_types.cpp

@@ -18,7 +18,7 @@
 // This also deliberately doesn't use the below StringList type alias to test
 // that MAKE_OPAQUE can handle a type containing a `,`.  (The `std::allocator`
 // bit is just the default `std::vector` allocator).
-PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);
+PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>)
 
 using StringList = std::vector<std::string, std::allocator<std::string>>;
 

tests/test_pytypes.cpp

@@ -13,6 +13,14 @@
 
 #include <utility>
 
+//__has_include has been part of C++17, no need to check it
+#if defined(PYBIND11_CPP20) && __has_include(<ranges>)
+#    if !defined(PYBIND11_COMPILER_CLANG) || __clang_major__ >= 16 // llvm/llvm-project#52696
+#        define PYBIND11_TEST_PYTYPES_HAS_RANGES
+#        include <ranges>
+#    endif
+#endif
+
 namespace external {
 namespace detail {
 bool check(PyObject *o) { return PyFloat_Check(o) != 0; }
@@ -923,4 +931,59 @@ TEST_SUBMODULE(pytypes, m) {
 #else
     m.attr("defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL") = false;
 #endif
+
+#if defined(PYBIND11_TEST_PYTYPES_HAS_RANGES)
+
+    // test_tuple_ranges
+    m.def("tuple_iterator_default_initialization", []() {
+        using TupleIterator = decltype(std::declval<py::tuple>().begin());
+        static_assert(std::random_access_iterator<TupleIterator>);
+        return TupleIterator{} == TupleIterator{};
+    });
+
+    m.def("transform_tuple_plus_one", [](py::tuple &tpl) {
+        py::list ret{};
+        for (auto it : tpl | std::views::transform([](auto &o) { return py::cast<int>(o) + 1; })) {
+            ret.append(py::int_(it));
+        }
+        return ret;
+    });
+
+    // test_list_ranges
+    m.def("list_iterator_default_initialization", []() {
+        using ListIterator = decltype(std::declval<py::list>().begin());
+        static_assert(std::random_access_iterator<ListIterator>);
+        return ListIterator{} == ListIterator{};
+    });
+
+    m.def("transform_list_plus_one", [](py::list &lst) {
+        py::list ret{};
+        for (auto it : lst | std::views::transform([](auto &o) { return py::cast<int>(o) + 1; })) {
+            ret.append(py::int_(it));
+        }
+        return ret;
+    });
+
+    // test_dict_ranges
+    m.def("dict_iterator_default_initialization", []() {
+        using DictIterator = decltype(std::declval<py::dict>().begin());
+        static_assert(std::forward_iterator<DictIterator>);
+        return DictIterator{} == DictIterator{};
+    });
+
+    m.def("transform_dict_plus_one", [](py::dict &dct) {
+        py::list ret{};
+        for (auto it : dct | std::views::transform([](auto &o) {
+                           return std::pair{py::cast<int>(o.first) + 1,
+                                            py::cast<int>(o.second) + 1};
+                       })) {
+            ret.append(py::make_tuple(py::int_(it.first), py::int_(it.second)));
+        }
+        return ret;
+    });
+
+    m.attr("defined_PYBIND11_TEST_PYTYPES_HAS_RANGES") = true;
+#else
+    m.attr("defined_PYBIND11_TEST_PYTYPES_HAS_RANGES") = false;
+#endif
 }

tests/test_pytypes.py

@@ -1026,7 +1026,7 @@ def test_optional_object_annotations(doc):
 
 @pytest.mark.skipif(
     not m.defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL,
-    reason="C++20 feature not available.",
+    reason="C++20 non-type template args feature not available.",
 )
 def test_literal(doc):
     assert (
@@ -1037,7 +1037,7 @@ def test_literal(doc):
 
 @pytest.mark.skipif(
     not m.defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL,
-    reason="C++20 feature not available.",
+    reason="C++20 non-type template args feature not available.",
 )
 def test_typevar(doc):
     assert (
@@ -1048,3 +1048,45 @@ def test_typevar(doc):
     assert doc(m.annotate_listT_to_T) == "annotate_listT_to_T(arg0: list[T]) -> T"
 
     assert doc(m.annotate_object_to_T) == "annotate_object_to_T(arg0: object) -> T"
+
+
+@pytest.mark.skipif(
+    not m.defined_PYBIND11_TEST_PYTYPES_HAS_RANGES,
+    reason="<ranges> not available.",
+)
+@pytest.mark.parametrize(
+    ("tested_tuple", "expected"),
+    [((1,), [2]), ((3, 4), [4, 5]), ((7, 8, 9), [8, 9, 10])],
+)
+def test_tuple_ranges(tested_tuple, expected):
+    assert m.tuple_iterator_default_initialization()
+    assert m.transform_tuple_plus_one(tested_tuple) == expected
+
+
+@pytest.mark.skipif(
+    not m.defined_PYBIND11_TEST_PYTYPES_HAS_RANGES,
+    reason="<ranges> not available.",
+)
+@pytest.mark.parametrize(
+    ("tested_list", "expected"), [([1], [2]), ([3, 4], [4, 5]), ([7, 8, 9], [8, 9, 10])]
+)
+def test_list_ranges(tested_list, expected):
+    assert m.list_iterator_default_initialization()
+    assert m.transform_list_plus_one(tested_list) == expected
+
+
+@pytest.mark.skipif(
+    not m.defined_PYBIND11_TEST_PYTYPES_HAS_RANGES,
+    reason="<ranges> not available.",
+)
+@pytest.mark.parametrize(
+    ("tested_dict", "expected"),
+    [
+        ({1: 2}, [(2, 3)]),
+        ({3: 4, 5: 6}, [(4, 5), (6, 7)]),
+        ({7: 8, 9: 10, 11: 12}, [(8, 9), (10, 11), (12, 13)]),
+    ],
+)
+def test_dict_ranges(tested_dict, expected):
+    assert m.dict_iterator_default_initialization()
+    assert m.transform_dict_plus_one(tested_dict) == expected

tests/test_sequences_and_iterators.cpp

@@ -86,8 +86,8 @@ private:
 };
 using NonCopyableIntPair = std::pair<NonCopyableInt, NonCopyableInt>;
 
-PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableInt>);
-PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>);
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableInt>)
+PYBIND11_MAKE_OPAQUE(std::vector<NonCopyableIntPair>)
 
 template <typename PythonType>
 py::list test_random_access_iterator(PythonType x) {

tests/test_smart_ptr.cpp

@@ -11,6 +11,9 @@
 #include "object.h"
 #include "pybind11_tests.h"
 
+// This breaks on PYBIND11_DECLARE_HOLDER_TYPE
+PYBIND11_WARNING_DISABLE_GCC("-Wpedantic")
+
 namespace {
 
 // This is just a wrapper around unique_ptr, but with extra fields to deliberately bloat up the
@@ -279,13 +282,13 @@ struct holder_helper<ref<T>> {
 } // namespace PYBIND11_NAMESPACE
 
 // Make pybind aware of the ref-counted wrapper type (s):
-PYBIND11_DECLARE_HOLDER_TYPE(T, ref<T>, true);
+PYBIND11_DECLARE_HOLDER_TYPE(T, ref<T>, true)
 // The following is not required anymore for std::shared_ptr, but it should compile without error:
-PYBIND11_DECLARE_HOLDER_TYPE(T, std::shared_ptr<T>);
-PYBIND11_DECLARE_HOLDER_TYPE(T, huge_unique_ptr<T>);
-PYBIND11_DECLARE_HOLDER_TYPE(T, custom_unique_ptr<T>);
-PYBIND11_DECLARE_HOLDER_TYPE(T, shared_ptr_with_addressof_operator<T>);
-PYBIND11_DECLARE_HOLDER_TYPE(T, unique_ptr_with_addressof_operator<T>);
+PYBIND11_DECLARE_HOLDER_TYPE(T, std::shared_ptr<T>)
+PYBIND11_DECLARE_HOLDER_TYPE(T, huge_unique_ptr<T>)
+PYBIND11_DECLARE_HOLDER_TYPE(T, custom_unique_ptr<T>)
+PYBIND11_DECLARE_HOLDER_TYPE(T, shared_ptr_with_addressof_operator<T>)
+PYBIND11_DECLARE_HOLDER_TYPE(T, unique_ptr_with_addressof_operator<T>)
 
 TEST_SUBMODULE(smart_ptr, m) {
     // Please do not interleave `struct` and `class` definitions with bindings code,

tests/test_stl.cpp

@@ -59,7 +59,7 @@ struct visit_helper<boost::variant> {
 } // namespace PYBIND11_NAMESPACE
 #endif
 
-PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);
+PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>)
 
 /// Issue #528: templated constructor
 struct TplCtorClass {
@@ -201,6 +201,23 @@ TEST_SUBMODULE(stl, m) {
     m.def("cast_array", []() { return std::array<int, 2>{{1, 2}}; });
     m.def("load_array", [](const std::array<int, 2> &a) { return a[0] == 1 && a[1] == 2; });
 
+    struct NoDefaultCtor {
+        explicit constexpr NoDefaultCtor(int val) : val{val} {}
+        int val;
+    };
+
+    struct NoDefaultCtorArray {
+        explicit constexpr NoDefaultCtorArray(int i)
+            : arr{{NoDefaultCtor(10 + i), NoDefaultCtor(20 + i)}} {}
+        std::array<NoDefaultCtor, 2> arr;
+    };
+
+    // test_array_no_default_ctor
+    py::class_<NoDefaultCtor>(m, "NoDefaultCtor").def_readonly("val", &NoDefaultCtor::val);
+    py::class_<NoDefaultCtorArray>(m, "NoDefaultCtorArray")
+        .def(py::init<int>())
+        .def_readwrite("arr", &NoDefaultCtorArray::arr);
+
     // test_valarray
     m.def("cast_valarray", []() { return std::valarray<int>{1, 4, 9}; });
     m.def("load_valarray", [](const std::valarray<int> &v) {

tests/test_stl.py

@@ -48,6 +48,13 @@ def test_array(doc):
     )
 
 
+def test_array_no_default_ctor():
+    lst = m.NoDefaultCtorArray(3)
+    assert [e.val for e in lst.arr] == [13, 23]
+    lst.arr = m.NoDefaultCtorArray(4).arr
+    assert [e.val for e in lst.arr] == [14, 24]
+
+
 def test_valarray(doc):
     """std::valarray <-> list"""
     lst = m.cast_valarray()

tests/test_tagbased_polymorphic.cpp

@@ -145,4 +145,4 @@ TEST_SUBMODULE(tagbased_polymorphic, m) {
         .def(py::init<std::string>())
         .def("purr", &Panther::purr);
     m.def("create_zoo", &create_zoo);
-};
+}

tests/test_virtual_functions.cpp

@@ -589,4 +589,4 @@ void initialize_inherited_virtuals(py::module_ &m) {
     // Fix issue #1454 (crash when acquiring/releasing GIL on another thread in Python 2.7)
     m.def("test_gil", &test_gil);
     m.def("test_gil_from_thread", &test_gil_from_thread);
-};
+}

tests/test_warnings.cpp

@@ -0,0 +1,46 @@
+/*
+    tests/test_warnings.cpp -- usage of warnings::warn() and warnings categories.
+
+    Copyright (c) 2024 Jan Iwaszkiewicz <jiwaszkiewicz6@gmail.com>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include <pybind11/warnings.h>
+
+#include "pybind11_tests.h"
+
+#include <utility>
+
+TEST_SUBMODULE(warnings_, m) {
+
+    // Test warning mechanism base
+    m.def("warn_and_return_value", []() {
+        std::string message = "This is simple warning";
+        py::warnings::warn(message.c_str(), PyExc_Warning);
+        return 21;
+    });
+
+    m.def("warn_with_default_category", []() { py::warnings::warn("This is RuntimeWarning"); });
+
+    m.def("warn_with_different_category",
+          []() { py::warnings::warn("This is FutureWarning", PyExc_FutureWarning); });
+
+    m.def("warn_with_invalid_category",
+          []() { py::warnings::warn("Invalid category", PyExc_Exception); });
+
+    // Test custom warnings
+    PYBIND11_CONSTINIT static py::gil_safe_call_once_and_store<py::object> ex_storage;
+    ex_storage.call_once_and_store_result([&]() {
+        return py::warnings::new_warning_type(m, "CustomWarning", PyExc_DeprecationWarning);
+    });
+
+    m.def("warn_with_custom_type", []() {
+        py::warnings::warn("This is CustomWarning", ex_storage.get_stored());
+        return 37;
+    });
+
+    m.def("register_duplicate_warning",
+          [m]() { py::warnings::new_warning_type(m, "CustomWarning", PyExc_RuntimeWarning); });
+}

tests/test_warnings.py

@@ -0,0 +1,68 @@
+from __future__ import annotations
+
+import warnings
+
+import pytest
+
+import pybind11_tests  # noqa: F401
+from pybind11_tests import warnings_ as m
+
+
+@pytest.mark.parametrize(
+    ("expected_category", "expected_message", "expected_value", "module_function"),
+    [
+        (Warning, "This is simple warning", 21, m.warn_and_return_value),
+        (RuntimeWarning, "This is RuntimeWarning", None, m.warn_with_default_category),
+        (FutureWarning, "This is FutureWarning", None, m.warn_with_different_category),
+    ],
+)
+def test_warning_simple(
+    expected_category, expected_message, expected_value, module_function
+):
+    with pytest.warns(Warning) as excinfo:
+        value = module_function()
+
+    assert issubclass(excinfo[0].category, expected_category)
+    assert str(excinfo[0].message) == expected_message
+    assert value == expected_value
+
+
+def test_warning_wrong_subclass_fail():
+    with pytest.raises(Exception) as excinfo:
+        m.warn_with_invalid_category()
+
+    assert issubclass(excinfo.type, RuntimeError)
+    assert (
+        str(excinfo.value)
+        == "pybind11::warnings::warn(): cannot raise warning, category must be a subclass of PyExc_Warning!"
+    )
+
+
+def test_warning_double_register_fail():
+    with pytest.raises(Exception) as excinfo:
+        m.register_duplicate_warning()
+
+    assert issubclass(excinfo.type, RuntimeError)
+    assert (
+        str(excinfo.value)
+        == 'pybind11::warnings::new_warning_type(): an attribute with name "CustomWarning" exists already.'
+    )
+
+
+def test_warning_register():
+    assert m.CustomWarning is not None
+
+    with pytest.warns(m.CustomWarning) as excinfo:
+        warnings.warn("This is warning from Python!", m.CustomWarning, stacklevel=1)
+
+    assert issubclass(excinfo[0].category, DeprecationWarning)
+    assert str(excinfo[0].message) == "This is warning from Python!"
+
+
+def test_warning_custom():
+    with pytest.warns(m.CustomWarning) as excinfo:
+        value = m.warn_with_custom_type()
+
+    assert issubclass(excinfo[0].category, DeprecationWarning)
+    assert str(excinfo[0].message) == "This is CustomWarning"
+    assert value == 37

tools/pybind11Common.cmake

@@ -18,11 +18,7 @@ Adds the following functions::
 
 #]======================================================]
 
-# CMake 3.10 has an include_guard command, but we can't use that yet
-# include_guard(global) (pre-CMake 3.10)
-if(TARGET pybind11::pybind11)
-  return()
-endif()
+include_guard(GLOBAL)
 
 # If we are in subdirectory mode, all IMPORTED targets must be GLOBAL. If we
 # are in CONFIG mode, they should be "normal" targets instead.
@@ -80,9 +76,6 @@ set_property(
 # Please open an issue if you need to use it; it will be removed if no one
 # needs it.
 if(CMAKE_SYSTEM_NAME MATCHES Emscripten AND NOT _pybind11_no_exceptions)
-  if(CMAKE_VERSION VERSION_LESS 3.13)
-    message(WARNING "CMake 3.13+ is required to build for Emscripten. Some flags will be missing")
-  else()
   if(is_config)
     set(_tmp_config_target pybind11::pybind11_headers)
   else()
@@ -99,28 +92,15 @@ if(CMAKE_SYSTEM_NAME MATCHES Emscripten AND NOT _pybind11_no_exceptions)
     PROPERTY INTERFACE_COMPILE_OPTIONS -fexceptions)
   unset(_tmp_config_target)
 endif()
-endif()
 
 # --------------------------- link helper ---------------------------
 
 add_library(pybind11::python_link_helper IMPORTED INTERFACE ${optional_global})
 
-if(CMAKE_VERSION VERSION_LESS 3.13)
-  # In CMake 3.11+, you can set INTERFACE properties via the normal methods, and
-  # this would be simpler.
-  set_property(
-    TARGET pybind11::python_link_helper
-    APPEND
-    PROPERTY INTERFACE_LINK_LIBRARIES "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
-else()
-  # link_options was added in 3.13+
-  # This is safer, because you are ensured the deduplication pass in CMake will not consider
-  # these separate and remove one but not the other.
 set_property(
   TARGET pybind11::python_link_helper
   APPEND
   PROPERTY INTERFACE_LINK_OPTIONS "$<$<PLATFORM_ID:Darwin>:LINKER:-undefined,dynamic_lookup>")
-endif()
 
 # ------------------------ Windows extras -------------------------
 
@@ -136,12 +116,6 @@ if(MSVC) # That's also clang-cl
 
   # /MP enables multithreaded builds (relevant when there are many files) for MSVC
   if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC") # no Clang no Intel
-    if(CMAKE_VERSION VERSION_LESS 3.11)
-      set_property(
-        TARGET pybind11::windows_extras
-        APPEND
-        PROPERTY INTERFACE_COMPILE_OPTIONS $<$<NOT:$<CONFIG:Debug>>:/MP>)
-    else()
     # Only set these options for C++ files.  This is important so that, for
     # instance, projects that include other types of source files like CUDA
     # .cu files don't get these options propagated to nvcc since that would
@@ -149,9 +123,7 @@ if(MSVC) # That's also clang-cl
     set_property(
       TARGET pybind11::windows_extras
       APPEND
-        PROPERTY INTERFACE_COMPILE_OPTIONS
-                 $<$<NOT:$<CONFIG:Debug>>:$<$<COMPILE_LANGUAGE:CXX>:/MP>>)
-    endif()
+      PROPERTY INTERFACE_COMPILE_OPTIONS $<$<NOT:$<CONFIG:Debug>>:$<$<COMPILE_LANGUAGE:CXX>:/MP>>)
   endif()
 endif()
 
@@ -397,11 +369,7 @@ function(_pybind11_generate_lto target prefer_thin_lto)
     set(is_debug "$<OR:$<CONFIG:Debug>,$<CONFIG:RelWithDebInfo>>")
     set(not_debug "$<NOT:${is_debug}>")
     set(cxx_lang "$<COMPILE_LANGUAGE:CXX>")
-    if(MSVC AND CMAKE_VERSION VERSION_LESS 3.11)
-      set(genex "${not_debug}")
-    else()
     set(genex "$<AND:${not_debug},${cxx_lang}>")
-    endif()
     set_property(
       TARGET ${target}
       APPEND
@@ -416,18 +384,11 @@ function(_pybind11_generate_lto target prefer_thin_lto)
   endif()
 
   if(PYBIND11_LTO_LINKER_FLAGS)
-    if(CMAKE_VERSION VERSION_LESS 3.11)
-      set_property(
-        TARGET ${target}
-        APPEND
-        PROPERTY INTERFACE_LINK_LIBRARIES "$<${not_debug}:${PYBIND11_LTO_LINKER_FLAGS}>")
-    else()
     set_property(
       TARGET ${target}
       APPEND
       PROPERTY INTERFACE_LINK_OPTIONS "$<${not_debug}:${PYBIND11_LTO_LINKER_FLAGS}>")
   endif()
-  endif()
 endfunction()
 
 if(NOT DEFINED CMAKE_INTERPROCEDURAL_OPTIMIZATION)

tools/pybind11GuessPythonExtSuffix.cmake

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.15...3.30)
 
 function(pybind11_guess_python_module_extension python)
 

tools/pybind11NewTools.cmake

@@ -5,10 +5,6 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-if(CMAKE_VERSION VERSION_LESS 3.12)
-  message(FATAL_ERROR "You cannot use the new FindPython module with CMake < 3.12")
-endif()
-
 include_guard(DIRECTORY)
 
 get_property(
@@ -236,7 +232,6 @@ if(TARGET ${_Python}::Python)
     PROPERTY INTERFACE_LINK_LIBRARIES ${_Python}::Python)
 endif()
 
-# CMake 3.15+ has this
 if(TARGET ${_Python}::Module)
   set_property(
     TARGET pybind11::module
@@ -279,10 +274,6 @@ function(pybind11_add_module target_name)
     target_link_libraries(${target_name} PRIVATE pybind11::embed)
   endif()
 
-  if(MSVC)
-    target_link_libraries(${target_name} PRIVATE pybind11::windows_extras)
-  endif()
-
   # -fvisibility=hidden is required to allow multiple modules compiled against
   # different pybind versions to work properly, and for some features (e.g.
   # py::module_local).  We force it on everything inside the `pybind11`

tools/pybind11Tools.cmake

@@ -5,13 +5,7 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-# include_guard(global) (pre-CMake 3.10)
-if(TARGET pybind11::python_headers)
-  return()
-endif()
-
-# Built-in in CMake 3.5+
-include(CMakeParseArguments)
+include_guard(GLOBAL)
 
 if(pybind11_FIND_QUIETLY)
   set(_pybind11_quiet QUIET)
@@ -116,22 +110,6 @@ if(PYTHON_IS_DEBUG)
     PROPERTY INTERFACE_COMPILE_DEFINITIONS Py_DEBUG)
 endif()
 
-# The <3.11 code here does not support release/debug builds at the same time, like on vcpkg
-if(CMAKE_VERSION VERSION_LESS 3.11)
-  set_property(
-    TARGET pybind11::module
-    APPEND
-    PROPERTY
-      INTERFACE_LINK_LIBRARIES
-      pybind11::python_link_helper
-      "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>"
-  )
-
-  set_property(
-    TARGET pybind11::embed
-    APPEND
-    PROPERTY INTERFACE_LINK_LIBRARIES pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
-else()
 # The IMPORTED INTERFACE library here is to ensure that "debug" and "release" get processed outside
 # of a generator expression - https://gitlab.kitware.com/cmake/cmake/-/issues/18424, as they are
 # target_link_library keywords rather than real libraries.
@@ -145,7 +123,6 @@ else()
 
 target_link_libraries(pybind11::embed INTERFACE pybind11::pybind11
                                                 pybind11::_ClassicPythonLibraries)
-endif()
 
 function(pybind11_extension name)
   # The prefix and extension are provided by FindPythonLibsNew.cmake

tools/test-pybind11GuessPythonExtSuffix.cmake

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.15...3.30)
 
 # Tests for pybind11_guess_python_module_extension
 # Run using `cmake -P tools/test-pybind11GuessPythonExtSuffix.cmake`