Merge branch 'master' into annotated_any

.github/dependabot.yml

@@ -4,4 +4,12 @@ updates:
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      interval: "daily"
+      interval: "weekly"
+    groups:
+      actions:
+        patterns:
+          - "*"
+    ignore:
+      - dependency-name: actions/checkout
+        versions:
+          - "<5"

.github/workflows/ci.yml

@@ -86,11 +86,11 @@ jobs:
       run: brew install boost
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
 
     - name: Cache wheels
       if: runner.os == 'macOS'
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         # This path is specific to macOS - we really only need it for PyPy NumPy wheels
         # See https://github.com/actions/cache/blob/master/examples.md#python---pip
@@ -108,12 +108,14 @@ jobs:
       run: python -m pip install pytest-github-actions-annotate-failures
 
     # First build - C++11 mode and inplace
-    # More-or-less randomly adding -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON here.
+    # More-or-less randomly adding -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON here
+    # (same for PYBIND11_NUMPY_1_ONLY, but requires a NumPy 1.x at runtime).
     - name: Configure C++11 ${{ matrix.args }}
       run: >
         cmake -S . -B .
         -DPYBIND11_WERROR=ON
         -DPYBIND11_SIMPLE_GIL_MANAGEMENT=ON
+        -DPYBIND11_NUMPY_1_ONLY=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
@@ -138,11 +140,13 @@ jobs:
 
     # Second build - C++17 mode and in a build directory
     # More-or-less randomly adding -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF here.
+    # (same for PYBIND11_NUMPY_1_ONLY, but requires a NumPy 1.x at runtime).
     - name: Configure C++17
       run: >
         cmake -S . -B build2
         -DPYBIND11_WERROR=ON
         -DPYBIND11_SIMPLE_GIL_MANAGEMENT=OFF
+        -DPYBIND11_NUMPY_1_ONLY=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
@@ -214,11 +218,11 @@ jobs:
         debug: ${{ matrix.python-debug }}
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
 
     - name: Valgrind cache
       if: matrix.valgrind
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       id: cache-valgrind
       with:
         path: valgrind
@@ -484,7 +488,7 @@ jobs:
       run: python3 -m pip install --upgrade pip
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
 
     - name: Configure
       shell: bash
@@ -529,8 +533,6 @@ jobs:
   # Testing on ICC using the oneAPI apt repo
   icc:
     runs-on: ubuntu-20.04
-    strategy:
-      fail-fast: false
 
     name: "🐍 3 • ICC latest • x64"
 
@@ -662,6 +664,11 @@ jobs:
       run: |
         python3 -m pip install cmake -r tests/requirements.txt
 
+    - name: Ensure NumPy 2 is used (required Python >= 3.9)
+      if: matrix.container == 'almalinux:9'
+      run: |
+        python3 -m pip install 'numpy>=2.0.0b1' 'scipy>=1.13.0rc1'
+
     - name: Configure
       shell: bash
       run: >
@@ -797,10 +804,10 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.12.1
+      uses: ilammy/msvc-dev-cmd@v1.13.0
       with:
         arch: x86
 
@@ -850,10 +857,10 @@ jobs:
         architecture: x86
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
 
     - name: Prepare MSVC
-      uses: ilammy/msvc-dev-cmd@v1.12.1
+      uses: ilammy/msvc-dev-cmd@v1.13.0
       with:
         arch: x86
 
@@ -897,11 +904,13 @@ jobs:
         python-version: ${{ matrix.python }}
 
     - name: Prepare env
+      # Ensure use of NumPy 2 (via NumPy nightlies but can be changed soon)
       run: |
         python3 -m pip install -r tests/requirements.txt
+        python3 -m pip install 'numpy>=2.0.0b1' 'scipy>=1.13.0rc1'
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
 
     - name: Configure C++20
       run: >
@@ -959,7 +968,6 @@ jobs:
           mingw-w64-${{matrix.env}}-gcc
           mingw-w64-${{matrix.env}}-python-pip
           mingw-w64-${{matrix.env}}-python-numpy
-          mingw-w64-${{matrix.env}}-python-scipy
           mingw-w64-${{matrix.env}}-cmake
           mingw-w64-${{matrix.env}}-make
           mingw-w64-${{matrix.env}}-python-pytest
@@ -967,6 +975,14 @@ jobs:
           mingw-w64-${{matrix.env}}-boost
           mingw-w64-${{matrix.env}}-catch
 
+    - uses: msys2/setup-msys2@v2
+      if: matrix.sys == 'mingw64'
+      with:
+        msystem: ${{matrix.sys}}
+        install: >-
+          git
+          mingw-w64-${{matrix.env}}-python-scipy
+
     - uses: actions/checkout@v4
 
     - name: Configure C++11
@@ -1058,7 +1074,7 @@ jobs:
           python-version: ${{ matrix.python }}
 
       - name: Update CMake
-        uses: jwlawson/actions-setup-cmake@v1.14
+        uses: jwlawson/actions-setup-cmake@v2.0
 
       - name: Install ninja-build tool
         uses: seanmiddleditch/gha-setup-ninja@v4
@@ -1128,7 +1144,7 @@ jobs:
         run: clang++ --version
 
       - name: Update CMake
-        uses: jwlawson/actions-setup-cmake@v1.14
+        uses: jwlawson/actions-setup-cmake@v2.0
 
       - name: Run pip installs
         run: |

.github/workflows/configure.yml

@@ -63,7 +63,7 @@ jobs:
     # An action for adding a specific version of CMake:
     #   https://github.com/jwlawson/actions-setup-cmake
     - name: Setup CMake ${{ matrix.cmake }}
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
       with:
         cmake-version: ${{ matrix.cmake }}
 

.github/workflows/format.yml

@@ -31,7 +31,7 @@ jobs:
         python-version: "3.x"
     - name: Add matchers
       run: echo "::add-matcher::$GITHUB_WORKSPACE/.github/matchers/pylint.json"
-    - uses: pre-commit/action@v3.0.0
+    - uses: pre-commit/action@v3.0.1
       with:
         # Slow hooks are marked with manual - slow is okay here, run them too
         extra_args: --hook-stage manual --all-files

.github/workflows/upstream.yml

@@ -36,7 +36,7 @@ jobs:
       run: sudo apt-get install libboost-dev
 
     - name: Update CMake
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0
 
     - name: Run pip installs
       run: |

.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: v0.1.6
+  rev: v0.2.0
   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: "v1.7.1"
+  rev: "v1.8.0"
   hooks:
   - id: mypy
     args: []
@@ -93,7 +93,7 @@ repos:
 
 # Avoid directional quotes
 - repo: https://github.com/sirosen/texthooks
-  rev: "0.6.3"
+  rev: "0.6.4"
   hooks:
   - id: fix-ligatures
   - id: fix-smartquotes
@@ -142,7 +142,14 @@ repos:
 
 # PyLint has native support - not always usable, but works for us
 - repo: https://github.com/PyCQA/pylint
-  rev: "v3.0.1"
+  rev: "v3.0.3"
   hooks:
   - id: pylint
     files: ^pybind11
+
+- repo: https://github.com/python-jsonschema/check-jsonschema
+  rev: 0.28.0
+  hooks:
+  - id: check-readthedocs
+  - id: check-github-workflows
+  - id: check-dependabot

CMakeLists.txt

@@ -109,6 +109,8 @@ option(PYBIND11_TEST "Build pybind11 test suite?" ${PYBIND11_MASTER_PROJECT})
 option(PYBIND11_NOPYTHON "Disable search for Python" OFF)
 option(PYBIND11_SIMPLE_GIL_MANAGEMENT
        "Use simpler GIL management logic that does not support disassociation" OFF)
+option(PYBIND11_NUMPY_1_ONLY
+       "Disable NumPy 2 support to avoid changes to previous pybind11 versions." OFF)
 set(PYBIND11_INTERNALS_VERSION
     ""
     CACHE STRING "Override the ABI version, may be used to enable the unstable ABI.")
@@ -116,6 +118,9 @@ set(PYBIND11_INTERNALS_VERSION
 if(PYBIND11_SIMPLE_GIL_MANAGEMENT)
   add_compile_definitions(PYBIND11_SIMPLE_GIL_MANAGEMENT)
 endif()
+if(PYBIND11_NUMPY_1_ONLY)
+  add_compile_definitions(PYBIND11_NUMPY_1_ONLY)
+endif()
 
 cmake_dependent_option(
   USE_PYTHON_INCLUDE_DIR

docs/compiling.rst

@@ -639,3 +639,11 @@ cross-project dependency management. Additionally, it is able to autogenerate
 customizable pybind11-based wrappers by parsing C++ header files.
 
 .. [robotpy-build] https://robotpy-build.readthedocs.io
+
+[litgen]_ is an automatic python bindings generator with a focus on generating
+documented and discoverable bindings: bindings will nicely reproduce the documentation
+found in headers. It is is based on srcML (srcml.org), a highly scalable, multi-language
+parsing tool with a developer centric approach. The API that you want to expose to python
+must be C++14 compatible (but your implementation can use more modern constructs).
+
+.. [litgen] https://pthom.github.io/litgen

include/pybind11/cast.h

@@ -327,8 +327,9 @@ public:
             value = false;
             return true;
         }
-        if (convert || (std::strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name) == 0)) {
+        if (convert || is_numpy_bool(src)) {
-            // (allow non-implicit conversion for numpy booleans)
+            // (allow non-implicit conversion for numpy booleans), use strncmp
+            // since NumPy 1.x had an additional trailing underscore.
 
             Py_ssize_t res = -1;
             if (src.is_none()) {
@@ -360,6 +361,15 @@ public:
         return handle(src ? Py_True : Py_False).inc_ref();
     }
     PYBIND11_TYPE_CASTER(bool, const_name("bool"));
+
+private:
+    // Test if an object is a NumPy boolean (without fetching the type).
+    static inline bool is_numpy_bool(handle object) {
+        const char *type_name = Py_TYPE(object.ptr())->tp_name;
+        // Name changed to `numpy.bool` in NumPy 2, `numpy.bool_` is needed for 1.x support
+        return std::strcmp("numpy.bool", type_name) == 0
+               || std::strcmp("numpy.bool_", type_name) == 0;
+    }
 };
 
 // Helper class for UTF-{8,16,32} C++ stl strings:

include/pybind11/detail/common.h

@@ -296,6 +296,10 @@ PYBIND11_WARNING_DISABLE_MSVC(4505)
 #    undef copysign
 #endif
 
+#if defined(PYBIND11_NUMPY_1_ONLY)
+#    define PYBIND11_INTERNAL_NUMPY_1_ONLY_DETECTED
+#endif
+
 #if defined(PYPY_VERSION) && !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
 #    define PYBIND11_SIMPLE_GIL_MANAGEMENT
 #endif

include/pybind11/detail/internals.h

@@ -67,9 +67,14 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 // `Py_LIMITED_API` anyway.
 #    if PYBIND11_INTERNALS_VERSION > 4
 #        define PYBIND11_TLS_KEY_REF Py_tss_t &
-#        if defined(__GNUC__) && !defined(__INTEL_COMPILER)
+#        if defined(__clang__)
-// Clang on macOS warns due to `Py_tss_NEEDS_INIT` not specifying an initializer
+#            define PYBIND11_TLS_KEY_INIT(var)                                                    \
-// for every field.
+                _Pragma("clang diagnostic push")                                         /**/     \
+                    _Pragma("clang diagnostic ignored \"-Wmissing-field-initializers\"") /**/     \
+                    Py_tss_t var                                                                  \
+                    = Py_tss_NEEDS_INIT;                                                          \
+                _Pragma("clang diagnostic pop")
+#        elif defined(__GNUC__) && !defined(__INTEL_COMPILER)
 #            define PYBIND11_TLS_KEY_INIT(var)                                                    \
                 _Pragma("GCC diagnostic push")                                         /**/       \
                     _Pragma("GCC diagnostic ignored \"-Wmissing-field-initializers\"") /**/       \

include/pybind11/numpy.h

@@ -29,10 +29,15 @@
 #include <utility>
 #include <vector>
 
+#if defined(PYBIND11_NUMPY_1_ONLY) && !defined(PYBIND11_INTERNAL_NUMPY_1_ONLY_DETECTED)
+#    error PYBIND11_NUMPY_1_ONLY must be defined before any pybind11 header is included.
+#endif
+
 /* This will be true on all flat address space platforms and allows us to reduce the
    whole npy_intp / ssize_t / Py_intptr_t business down to just ssize_t for all size
    and dimension types (e.g. shape, strides, indexing), instead of inflicting this
-   upon the library user. */
+   upon the library user.
+   Note that NumPy 2 now uses ssize_t for `npy_intp` to simplify this. */
 static_assert(sizeof(::pybind11::ssize_t) == sizeof(Py_intptr_t), "ssize_t != Py_intptr_t");
 static_assert(std::is_signed<Py_intptr_t>::value, "Py_intptr_t must be signed");
 // We now can reinterpret_cast between py::ssize_t and Py_intptr_t (MSVC + PyPy cares)
@@ -59,7 +64,8 @@ struct handle_type_name<array> {
 template <typename type, typename SFINAE = void>
 struct npy_format_descriptor;
 
-struct PyArrayDescr_Proxy {
+/* NumPy 1 proxy (always includes legacy fields) */
+struct PyArrayDescr1_Proxy {
     PyObject_HEAD
     PyObject *typeobj;
     char kind;
@@ -74,6 +80,43 @@ struct PyArrayDescr_Proxy {
     PyObject *names;
 };
 
+#ifndef PYBIND11_NUMPY_1_ONLY
+struct PyArrayDescr_Proxy {
+    PyObject_HEAD
+    PyObject *typeobj;
+    char kind;
+    char type;
+    char byteorder;
+    char _former_flags;
+    int type_num;
+    /* Additional fields are NumPy version specific. */
+};
+#else
+/* NumPy 1.x only, we can expose all fields */
+using PyArrayDescr_Proxy = PyArrayDescr1_Proxy;
+#endif
+
+/* NumPy 2 proxy, including legacy fields */
+struct PyArrayDescr2_Proxy {
+    PyObject_HEAD
+    PyObject *typeobj;
+    char kind;
+    char type;
+    char byteorder;
+    char _former_flags;
+    int type_num;
+    std::uint64_t flags;
+    ssize_t elsize;
+    ssize_t alignment;
+    PyObject *metadata;
+    Py_hash_t hash;
+    void *reserved_null[2];
+    /* The following fields only exist if 0 <= type_num < 2056 */
+    char *subarray;
+    PyObject *fields;
+    PyObject *names;
+};
+
 struct PyArray_Proxy {
     PyObject_HEAD
     char *data;
@@ -137,6 +180,14 @@ PYBIND11_NOINLINE module_ import_numpy_core_submodule(const char *submodule_name
     object numpy_version = numpy_lib.attr("NumpyVersion")(version_string);
     int major_version = numpy_version.attr("major").cast<int>();
 
+#ifdef PYBIND11_NUMPY_1_ONLY
+    if (major_version >= 2) {
+        throw std::runtime_error(
+            "This extension was built with PYBIND11_NUMPY_1_ONLY defined, "
+            "but NumPy 2 is used in this process. For NumPy2 compatibility, "
+            "this extension needs to be rebuilt without the PYBIND11_NUMPY_1_ONLY define.");
+    }
+#endif
     /* `numpy.core` was renamed to `numpy._core` in NumPy 2.0 as it officially
         became a private module. */
     std::string numpy_core_path = major_version >= 2 ? "numpy._core" : "numpy.core";
@@ -209,6 +260,8 @@ struct npy_api {
             NPY_ULONG_, NPY_ULONGLONG_, NPY_UINT_),
     };
 
+    unsigned int PyArray_RUNTIME_VERSION_;
+
     struct PyArray_Dims {
         Py_intptr_t *ptr;
         int len;
@@ -247,6 +300,7 @@ struct npy_api {
     PyObject *(*PyArray_FromAny_)(PyObject *, PyObject *, int, int, int, PyObject *);
     int (*PyArray_DescrConverter_)(PyObject *, PyObject **);
     bool (*PyArray_EquivTypes_)(PyObject *, PyObject *);
+#ifdef PYBIND11_NUMPY_1_ONLY
     int (*PyArray_GetArrayParamsFromObject_)(PyObject *,
                                              PyObject *,
                                              unsigned char,
@@ -255,6 +309,7 @@ struct npy_api {
                                              Py_intptr_t *,
                                              PyObject **,
                                              PyObject *);
+#endif
     PyObject *(*PyArray_Squeeze_)(PyObject *);
     // Unused. Not removed because that affects ABI of the class.
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
@@ -272,7 +327,8 @@ private:
         API_PyArray_DescrFromScalar = 57,
         API_PyArray_FromAny = 69,
         API_PyArray_Resize = 80,
-        API_PyArray_CopyInto = 82,
+        // CopyInto was slot 82 and 50 was effectively an alias. NumPy 2 removed 82.
+        API_PyArray_CopyInto = 50,
         API_PyArray_NewCopy = 85,
         API_PyArray_NewFromDescr = 94,
         API_PyArray_DescrNewFromType = 96,
@@ -281,7 +337,9 @@ private:
         API_PyArray_View = 137,
         API_PyArray_DescrConverter = 174,
         API_PyArray_EquivTypes = 182,
+#ifdef PYBIND11_NUMPY_1_ONLY
         API_PyArray_GetArrayParamsFromObject = 278,
+#endif
         API_PyArray_SetBaseObject = 282
     };
 
@@ -296,7 +354,8 @@ private:
         npy_api api;
 #define DECL_NPY_API(Func) api.Func##_ = (decltype(api.Func##_)) api_ptr[API_##Func];
         DECL_NPY_API(PyArray_GetNDArrayCFeatureVersion);
-        if (api.PyArray_GetNDArrayCFeatureVersion_() < 0x7) {
+        api.PyArray_RUNTIME_VERSION_ = api.PyArray_GetNDArrayCFeatureVersion_();
+        if (api.PyArray_RUNTIME_VERSION_ < 0x7) {
             pybind11_fail("pybind11 numpy support requires numpy >= 1.7.0");
         }
         DECL_NPY_API(PyArray_Type);
@@ -315,7 +374,9 @@ private:
         DECL_NPY_API(PyArray_View);
         DECL_NPY_API(PyArray_DescrConverter);
         DECL_NPY_API(PyArray_EquivTypes);
+#ifdef PYBIND11_NUMPY_1_ONLY
         DECL_NPY_API(PyArray_GetArrayParamsFromObject);
+#endif
         DECL_NPY_API(PyArray_SetBaseObject);
 
 #undef DECL_NPY_API
@@ -337,6 +398,14 @@ inline const PyArrayDescr_Proxy *array_descriptor_proxy(const PyObject *ptr) {
     return reinterpret_cast<const PyArrayDescr_Proxy *>(ptr);
 }
 
+inline const PyArrayDescr1_Proxy *array_descriptor1_proxy(const PyObject *ptr) {
+    return reinterpret_cast<const PyArrayDescr1_Proxy *>(ptr);
+}
+
+inline const PyArrayDescr2_Proxy *array_descriptor2_proxy(const PyObject *ptr) {
+    return reinterpret_cast<const PyArrayDescr2_Proxy *>(ptr);
+}
+
 inline bool check_flags(const void *ptr, int flag) {
     return (flag == (array_proxy(ptr)->flags & flag));
 }
@@ -616,10 +685,32 @@ public:
     }
 
     /// Size of the data type in bytes.
+#ifdef PYBIND11_NUMPY_1_ONLY
     ssize_t itemsize() const { return detail::array_descriptor_proxy(m_ptr)->elsize; }
+#else
+    ssize_t itemsize() const {
+        if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
+            return detail::array_descriptor1_proxy(m_ptr)->elsize;
+        }
+        return detail::array_descriptor2_proxy(m_ptr)->elsize;
+    }
+#endif
 
     /// Returns true for structured data types.
+#ifdef PYBIND11_NUMPY_1_ONLY
     bool has_fields() const { return detail::array_descriptor_proxy(m_ptr)->names != nullptr; }
+#else
+    bool has_fields() const {
+        if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
+            return detail::array_descriptor1_proxy(m_ptr)->names != nullptr;
+        }
+        const auto *proxy = detail::array_descriptor2_proxy(m_ptr);
+        if (proxy->type_num < 0 || proxy->type_num >= 2056) {
+            return false;
+        }
+        return proxy->names != nullptr;
+    }
+#endif
 
     /// Single-character code for dtype's kind.
     /// For example, floating point types are 'f' and integral types are 'i'.
@@ -645,11 +736,29 @@ public:
     /// Single character for byteorder
     char byteorder() const { return detail::array_descriptor_proxy(m_ptr)->byteorder; }
 
-    /// Alignment of the data type
+/// Alignment of the data type
+#ifdef PYBIND11_NUMPY_1_ONLY
     int alignment() const { return detail::array_descriptor_proxy(m_ptr)->alignment; }
+#else
+    ssize_t alignment() const {
+        if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
+            return detail::array_descriptor1_proxy(m_ptr)->alignment;
+        }
+        return detail::array_descriptor2_proxy(m_ptr)->alignment;
+    }
+#endif
 
-    /// Flags for the array descriptor
+/// Flags for the array descriptor
+#ifdef PYBIND11_NUMPY_1_ONLY
     char flags() const { return detail::array_descriptor_proxy(m_ptr)->flags; }
+#else
+    std::uint64_t flags() const {
+        if (detail::npy_api::get().PyArray_RUNTIME_VERSION_ < 0x12) {
+            return (unsigned char) detail::array_descriptor1_proxy(m_ptr)->flags;
+        }
+        return detail::array_descriptor2_proxy(m_ptr)->flags;
+    }
+#endif
 
 private:
     static object &_dtype_from_pep3118() {
@@ -816,9 +925,7 @@ public:
     }
 
     /// Byte size of a single element
-    ssize_t itemsize() const {
+    ssize_t itemsize() const { return dtype().itemsize(); }
-        return detail::array_descriptor_proxy(detail::array_proxy(m_ptr)->descr)->elsize;
-    }
 
     /// Total number of bytes
     ssize_t nbytes() const { return size() * itemsize(); }

include/pybind11/stl.h

@@ -172,7 +172,7 @@ struct list_caster {
         auto s = reinterpret_borrow<sequence>(src);
         value.clear();
         reserve_maybe(s, &value);
-        for (auto it : s) {
+        for (const auto &it : s) {
             value_conv conv;
             if (!conv.load(it, convert)) {
                 return false;
@@ -247,7 +247,7 @@ public:
             return false;
         }
         size_t ctr = 0;
-        for (auto it : l) {
+        for (const auto &it : l) {
             value_conv conv;
             if (!conv.load(it, convert)) {
                 return false;

include/pybind11/stl_bind.h

@@ -645,49 +645,50 @@ auto map_if_insertion_operator(Class_ &cl, std::string const &name)
         "Return the canonical string representation of this map.");
 }
 
-template <typename KeyType>
 struct keys_view {
     virtual size_t len() = 0;
     virtual iterator iter() = 0;
-    virtual bool contains(const KeyType &k) = 0;
+    virtual bool contains(const handle &k) = 0;
-    virtual bool contains(const object &k) = 0;
     virtual ~keys_view() = default;
 };
 
-template <typename MappedType>
 struct values_view {
     virtual size_t len() = 0;
     virtual iterator iter() = 0;
     virtual ~values_view() = default;
 };
 
-template <typename KeyType, typename MappedType>
 struct items_view {
     virtual size_t len() = 0;
     virtual iterator iter() = 0;
     virtual ~items_view() = default;
 };
 
-template <typename Map, typename KeysView>
+template <typename Map>
-struct KeysViewImpl : public KeysView {
+struct KeysViewImpl : public detail::keys_view {
     explicit KeysViewImpl(Map &map) : map(map) {}
     size_t len() override { return map.size(); }
     iterator iter() override { return make_key_iterator(map.begin(), map.end()); }
-    bool contains(const typename Map::key_type &k) override { return map.find(k) != map.end(); }
+    bool contains(const handle &k) override {
-    bool contains(const object &) override { return false; }
+        try {
+            return map.find(k.template cast<typename Map::key_type>()) != map.end();
+        } catch (const cast_error &) {
+            return false;
+        }
+    }
     Map &map;
 };
 
-template <typename Map, typename ValuesView>
+template <typename Map>
-struct ValuesViewImpl : public ValuesView {
+struct ValuesViewImpl : public detail::values_view {
     explicit ValuesViewImpl(Map &map) : map(map) {}
     size_t len() override { return map.size(); }
     iterator iter() override { return make_value_iterator(map.begin(), map.end()); }
     Map &map;
 };
 
-template <typename Map, typename ItemsView>
+template <typename Map>
-struct ItemsViewImpl : public ItemsView {
+struct ItemsViewImpl : public detail::items_view {
     explicit ItemsViewImpl(Map &map) : map(map) {}
     size_t len() override { return map.size(); }
     iterator iter() override { return make_iterator(map.begin(), map.end()); }
@@ -700,11 +701,9 @@ template <typename Map, typename holder_type = std::unique_ptr<Map>, typename...
 class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&...args) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
-    using StrippedKeyType = detail::remove_cvref_t<KeyType>;
+    using KeysView = detail::keys_view;
-    using StrippedMappedType = detail::remove_cvref_t<MappedType>;
+    using ValuesView = detail::values_view;
-    using KeysView = detail::keys_view<StrippedKeyType>;
+    using ItemsView = detail::items_view;
-    using ValuesView = detail::values_view<StrippedMappedType>;
-    using ItemsView = detail::items_view<StrippedKeyType, StrippedMappedType>;
     using Class_ = class_<Map, holder_type>;
 
     // If either type is a non-module-local bound type then make the map binding non-local as well;
@@ -718,39 +717,20 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
     }
 
     Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
-    static constexpr auto key_type_descr = detail::make_caster<KeyType>::name;
-    static constexpr auto mapped_type_descr = detail::make_caster<MappedType>::name;
-    std::string key_type_name(key_type_descr.text), mapped_type_name(mapped_type_descr.text);
 
-    // If key type isn't properly wrapped, fall back to C++ names
+    // Wrap KeysView if it wasn't already wrapped
-    if (key_type_name == "%") {
-        key_type_name = detail::type_info_description(typeid(KeyType));
-    }
-    // Similarly for value type:
-    if (mapped_type_name == "%") {
-        mapped_type_name = detail::type_info_description(typeid(MappedType));
-    }
-
-    // Wrap KeysView[KeyType] if it wasn't already wrapped
     if (!detail::get_type_info(typeid(KeysView))) {
-        class_<KeysView> keys_view(
+        class_<KeysView> keys_view(scope, "KeysView", pybind11::module_local(local));
-            scope, ("KeysView[" + key_type_name + "]").c_str(), pybind11::module_local(local));
         keys_view.def("__len__", &KeysView::len);
         keys_view.def("__iter__",
                       &KeysView::iter,
                       keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
         );
-        keys_view.def("__contains__",
+        keys_view.def("__contains__", &KeysView::contains);
-                      static_cast<bool (KeysView::*)(const KeyType &)>(&KeysView::contains));
-        // Fallback for when the object is not of the key type
-        keys_view.def("__contains__",
-                      static_cast<bool (KeysView::*)(const object &)>(&KeysView::contains));
     }
     // Similarly for ValuesView:
     if (!detail::get_type_info(typeid(ValuesView))) {
-        class_<ValuesView> values_view(scope,
+        class_<ValuesView> values_view(scope, "ValuesView", pybind11::module_local(local));
-                                       ("ValuesView[" + mapped_type_name + "]").c_str(),
-                                       pybind11::module_local(local));
         values_view.def("__len__", &ValuesView::len);
         values_view.def("__iter__",
                         &ValuesView::iter,
@@ -759,10 +739,7 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
     }
     // Similarly for ItemsView:
     if (!detail::get_type_info(typeid(ItemsView))) {
-        class_<ItemsView> items_view(
+        class_<ItemsView> items_view(scope, "ItemsView", pybind11::module_local(local));
-            scope,
-            ("ItemsView[" + key_type_name + ", ").append(mapped_type_name + "]").c_str(),
-            pybind11::module_local(local));
         items_view.def("__len__", &ItemsView::len);
         items_view.def("__iter__",
                        &ItemsView::iter,
@@ -788,25 +765,19 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
 
     cl.def(
         "keys",
-        [](Map &m) {
+        [](Map &m) { return std::unique_ptr<KeysView>(new detail::KeysViewImpl<Map>(m)); },
-            return std::unique_ptr<KeysView>(new detail::KeysViewImpl<Map, KeysView>(m));
-        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def(
         "values",
-        [](Map &m) {
+        [](Map &m) { return std::unique_ptr<ValuesView>(new detail::ValuesViewImpl<Map>(m)); },
-            return std::unique_ptr<ValuesView>(new detail::ValuesViewImpl<Map, ValuesView>(m));
-        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def(
         "items",
-        [](Map &m) {
+        [](Map &m) { return std::unique_ptr<ItemsView>(new detail::ItemsViewImpl<Map>(m)); },
-            return std::unique_ptr<ItemsView>(new detail::ItemsViewImpl<Map, ItemsView>(m));
-        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 

include/pybind11/typing.h

@@ -79,6 +79,13 @@ struct handle_type_name<typing::Tuple<>> {
     static constexpr auto name = const_name("tuple[()]");
 };
 
+template <typename T>
+struct handle_type_name<typing::Tuple<T, ellipsis>> {
+    // PEP 484 specifies this syntax for a variable-length tuple
+    static constexpr auto name
+        = const_name("tuple[") + make_caster<T>::name + const_name(", ...]");
+};
+
 template <typename K, typename V>
 struct handle_type_name<typing::Dict<K, V>> {
     static constexpr auto name = const_name("dict[") + make_caster<K>::name + const_name(", ")

tests/CMakeLists.txt

@@ -521,11 +521,15 @@ set(PYBIND11_TEST_PREFIX_COMMAND
     ""
     CACHE STRING "Put this before pytest, use for checkers and such")
 
+set(PYBIND11_PYTEST_ARGS
+    ""
+    CACHE STRING "Extra arguments for pytest")
+
 # A single command to compile and run the tests
 add_custom_target(
   pytest
   COMMAND ${PYBIND11_TEST_PREFIX_COMMAND} ${PYTHON_EXECUTABLE} -m pytest
-          ${PYBIND11_ABS_PYTEST_FILES}
+          ${PYBIND11_ABS_PYTEST_FILES} ${PYBIND11_PYTEST_ARGS}
   DEPENDS ${test_targets}
   WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
   USES_TERMINAL)

tests/conftest.py

@@ -218,4 +218,5 @@ def pytest_report_header(config):
         f" {pybind11_tests.cpp_std}"
         f" {pybind11_tests.PYBIND11_INTERNALS_ID}"
         f" PYBIND11_SIMPLE_GIL_MANAGEMENT={pybind11_tests.PYBIND11_SIMPLE_GIL_MANAGEMENT}"
+        f" PYBIND11_NUMPY_1_ONLY={pybind11_tests.PYBIND11_NUMPY_1_ONLY}"
     )

tests/pybind11_tests.cpp

@@ -80,10 +80,10 @@ PYBIND11_MODULE(pybind11_tests, m) {
 
     // Intentionally kept minimal to not create a maintenance chore
     // ("just enough" to be conclusive).
-#if defined(_MSC_FULL_VER)
+#if defined(__VERSION__)
-    m.attr("compiler_info") = "MSVC " PYBIND11_TOSTRING(_MSC_FULL_VER);
-#elif defined(__VERSION__)
     m.attr("compiler_info") = __VERSION__;
+#elif defined(_MSC_FULL_VER)
+    m.attr("compiler_info") = "MSVC " PYBIND11_TOSTRING(_MSC_FULL_VER);
 #else
     m.attr("compiler_info") = py::none();
 #endif
@@ -95,6 +95,12 @@ PYBIND11_MODULE(pybind11_tests, m) {
 #else
         false;
 #endif
+    m.attr("PYBIND11_NUMPY_1_ONLY") =
+#if defined(PYBIND11_NUMPY_1_ONLY)
+        true;
+#else
+        false;
+#endif
 
     bind_ConstructorStats(m);
 

tests/test_constants_and_functions.cpp

@@ -54,7 +54,11 @@ int f2(int x) noexcept(true) { return x + 2; }
 int f3(int x) noexcept(false) { return x + 3; }
 PYBIND11_WARNING_PUSH
 PYBIND11_WARNING_DISABLE_GCC("-Wdeprecated")
+#if defined(__clang_major__) && __clang_major__ >= 5
+PYBIND11_WARNING_DISABLE_CLANG("-Wdeprecated-dynamic-exception-spec")
+#else
 PYBIND11_WARNING_DISABLE_CLANG("-Wdeprecated")
+#endif
 // NOLINTNEXTLINE(modernize-use-noexcept)
 int f4(int x) throw() { return x + 4; } // Deprecated equivalent to noexcept(true)
 PYBIND11_WARNING_POP

tests/test_eigen_matrix.py

@@ -608,7 +608,9 @@ def test_both_ref_mutators():
 def test_nocopy_wrapper():
     # get_elem requires a column-contiguous matrix reference, but should be
     # callable with other types of matrix (via copying):
-    int_matrix_colmajor = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]], order="F")
+    int_matrix_colmajor = np.array(
+        [[1, 2, 3], [4, 5, 6], [7, 8, 9]], dtype="l", order="F"
+    )
     dbl_matrix_colmajor = np.array(
         int_matrix_colmajor, dtype="double", order="F", copy=True
     )

tests/test_exceptions.py

@@ -4,7 +4,7 @@ import pytest
 
 import env
 import pybind11_cross_module_tests as cm
-import pybind11_tests  # noqa: F401
+import pybind11_tests
 from pybind11_tests import exceptions as m
 
 
@@ -248,6 +248,11 @@ def test_nested_throws(capture):
     assert str(excinfo.value) == "this is a helper-defined translated exception"
 
 
+# TODO: Investigate this crash, see pybind/pybind11#5062 for background
+@pytest.mark.skipif(
+    sys.platform.startswith("win32") and "Clang" in pybind11_tests.compiler_info,
+    reason="Started segfaulting February 2024",
+)
 def test_throw_nested_exception():
     with pytest.raises(RuntimeError) as excinfo:
         m.throw_nested_exception()

tests/test_numpy_array.py

@@ -536,7 +536,12 @@ def test_format_descriptors_for_floating_point_types(test_func):
 @pytest.mark.parametrize("contiguity", [None, "C", "F"])
 @pytest.mark.parametrize("noconvert", [False, True])
 @pytest.mark.filterwarnings(
-    "ignore:Casting complex values to real discards the imaginary part:numpy.ComplexWarning"
+    "ignore:Casting complex values to real discards the imaginary part:"
+    + (
+        "numpy.exceptions.ComplexWarning"
+        if hasattr(np, "exceptions")
+        else "numpy.ComplexWarning"
+    )
 )
 def test_argument_conversions(forcecast, contiguity, noconvert):
     function_name = "accept_double"
@@ -583,7 +588,8 @@ def test_argument_conversions(forcecast, contiguity, noconvert):
 def test_dtype_refcount_leak():
     from sys import getrefcount
 
-    dtype = np.dtype(np.float_)
+    # Was np.float_ but that alias for float64 was removed in NumPy 2.
+    dtype = np.dtype(np.float64)
     a = np.array([1], dtype=dtype)
     before = getrefcount(dtype)
     m.ndim(a)

tests/test_numpy_dtypes.cpp

@@ -405,10 +405,35 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     });
 
     // test_dtype
+    // Below we use `L` for unsigned long as unfortunately the only name that
+    // works reliably on Both NumPy 2.x and old NumPy 1.x.
     std::vector<const char *> dtype_names{
-        "byte",    "short",   "intc",        "int_",  "longlong",   "ubyte",       "ushort",
+        "byte",
-        "uintc",   "uint",    "ulonglong",   "half",  "single",     "double",      "longdouble",
+        "short",
-        "csingle", "cdouble", "clongdouble", "bool_", "datetime64", "timedelta64", "object_"};
+        "intc",
+        "long",
+        "longlong",
+        "ubyte",
+        "ushort",
+        "uintc",
+        "L",
+        "ulonglong",
+        "half",
+        "single",
+        "double",
+        "longdouble",
+        "csingle",
+        "cdouble",
+        "clongdouble",
+        "bool_",
+        "datetime64",
+        "timedelta64",
+        "object_",
+        // platform dependent aliases (int_ and uint are also NumPy version dependent on windows)
+        "int_",
+        "uint",
+        "intp",
+        "uintp"};
 
     m.def("print_dtypes", []() {
         py::list l;

tests/test_numpy_dtypes.py

@@ -3,6 +3,7 @@ import re
 import pytest
 
 import env  # noqa: F401
+from pybind11_tests import PYBIND11_NUMPY_1_ONLY
 from pybind11_tests import numpy_dtypes as m
 
 np = pytest.importorskip("numpy")
@@ -172,13 +173,20 @@ def test_dtype(simple_dtype):
         np.zeros(1, m.trailing_padding_dtype())
     )
 
-    expected_chars = "bhilqBHILQefdgFDG?MmO"
+    expected_chars = list("bhilqBHILQefdgFDG?MmO")
-    assert m.test_dtype_kind() == list("iiiiiuuuuuffffcccbMmO")
+    # Note that int_ and uint size and mapping is NumPy version dependent:
+    expected_chars += [np.dtype(_).char for _ in ("int_", "uint", "intp", "uintp")]
+    assert m.test_dtype_kind() == list("iiiiiuuuuuffffcccbMmOiuiu")
     assert m.test_dtype_char_() == list(expected_chars)
     assert m.test_dtype_num() == [np.dtype(ch).num for ch in expected_chars]
     assert m.test_dtype_byteorder() == [np.dtype(ch).byteorder for ch in expected_chars]
     assert m.test_dtype_alignment() == [np.dtype(ch).alignment for ch in expected_chars]
-    assert m.test_dtype_flags() == [chr(np.dtype(ch).flags) for ch in expected_chars]
+    if not PYBIND11_NUMPY_1_ONLY:
+        assert m.test_dtype_flags() == [np.dtype(ch).flags for ch in expected_chars]
+    else:
+        assert m.test_dtype_flags() == [
+            chr(np.dtype(ch).flags) for ch in expected_chars
+        ]
 
 
 def test_recarray(simple_dtype, packed_dtype):

tests/test_pytypes.cpp

@@ -834,6 +834,8 @@ TEST_SUBMODULE(pytypes, m) {
 
     m.def("annotate_tuple_float_str", [](const py::typing::Tuple<py::float_, py::str> &) {});
     m.def("annotate_tuple_empty", [](const py::typing::Tuple<> &) {});
+    m.def("annotate_tuple_variable_length",
+          [](const py::typing::Tuple<py::float_, py::ellipsis> &) {});
     m.def("annotate_dict_str_int", [](const py::typing::Dict<py::str, int> &) {});
     m.def("annotate_list_int", [](const py::typing::List<int> &) {});
     m.def("annotate_set_str", [](const py::typing::Set<std::string> &) {});

tests/test_pytypes.py

@@ -911,6 +911,13 @@ def test_tuple_empty_annotations(doc):
     )
 
 
+def test_tuple_variable_length_annotations(doc):
+    assert (
+        doc(m.annotate_tuple_variable_length)
+        == "annotate_tuple_variable_length(arg0: tuple[float, ...]) -> None"
+    )
+
+
 def test_dict_annotations(doc):
     assert (
         doc(m.annotate_dict_str_int)

tests/test_smart_ptr.cpp

@@ -103,21 +103,26 @@ private:
     int value;
 };
 
+template <typename T>
+std::unordered_set<T *> &pointer_set() {
+    // https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables
+    static auto singleton = new std::unordered_set<T *>();
+    return *singleton;
+}
+
 // test_unique_nodelete
 // Object with a private destructor
-class MyObject4;
-std::unordered_set<MyObject4 *> myobject4_instances;
 class MyObject4 {
 public:
     explicit MyObject4(int value) : value{value} {
         print_created(this);
-        myobject4_instances.insert(this);
+        pointer_set<MyObject4>().insert(this);
     }
     int value;
 
     static void cleanupAllInstances() {
-        auto tmp = std::move(myobject4_instances);
+        auto tmp = std::move(pointer_set<MyObject4>());
-        myobject4_instances.clear();
+        pointer_set<MyObject4>().clear();
         for (auto *o : tmp) {
             delete o;
         }
@@ -125,7 +130,7 @@ public:
 
 private:
     ~MyObject4() {
-        myobject4_instances.erase(this);
+        pointer_set<MyObject4>().erase(this);
         print_destroyed(this);
     }
 };
@@ -133,19 +138,17 @@ private:
 // test_unique_deleter
 // Object with std::unique_ptr<T, D> where D is not matching the base class
 // Object with a protected destructor
-class MyObject4a;
-std::unordered_set<MyObject4a *> myobject4a_instances;
 class MyObject4a {
 public:
     explicit MyObject4a(int i) : value{i} {
         print_created(this);
-        myobject4a_instances.insert(this);
+        pointer_set<MyObject4a>().insert(this);
     };
     int value;
 
     static void cleanupAllInstances() {
-        auto tmp = std::move(myobject4a_instances);
+        auto tmp = std::move(pointer_set<MyObject4a>());
-        myobject4a_instances.clear();
+        pointer_set<MyObject4a>().clear();
         for (auto *o : tmp) {
             delete o;
         }
@@ -153,7 +156,7 @@ public:
 
 protected:
     virtual ~MyObject4a() {
-        myobject4a_instances.erase(this);
+        pointer_set<MyObject4a>().erase(this);
         print_destroyed(this);
     }
 };

tests/test_stl_binders.cpp

@@ -192,6 +192,16 @@ TEST_SUBMODULE(stl_binders, m) {
     py::bind_map<std::unordered_map<std::string, double const>>(m,
                                                                 "UnorderedMapStringDoubleConst");
 
+    // test_map_view_types
+    py::bind_map<std::map<std::string, float>>(m, "MapStringFloat");
+    py::bind_map<std::unordered_map<std::string, float>>(m, "UnorderedMapStringFloat");
+
+    py::bind_map<std::map<std::pair<double, int>, int32_t>>(m, "MapPairDoubleIntInt32");
+    py::bind_map<std::map<std::pair<double, int>, int64_t>>(m, "MapPairDoubleIntInt64");
+
+    py::bind_map<std::map<int, py::object>>(m, "MapIntObject");
+    py::bind_map<std::map<std::string, py::object>>(m, "MapStringObject");
+
     py::class_<E_nc>(m, "ENC").def(py::init<int>()).def_readwrite("value", &E_nc::value);
 
     // test_noncopyable_containers

tests/test_stl_binders.py

@@ -317,9 +317,9 @@ def test_map_view_types():
     map_string_double_const = m.MapStringDoubleConst()
     unordered_map_string_double_const = m.UnorderedMapStringDoubleConst()
 
-    assert map_string_double.keys().__class__.__name__ == "KeysView[str]"
+    assert map_string_double.keys().__class__.__name__ == "KeysView"
-    assert map_string_double.values().__class__.__name__ == "ValuesView[float]"
+    assert map_string_double.values().__class__.__name__ == "ValuesView"
-    assert map_string_double.items().__class__.__name__ == "ItemsView[str, float]"
+    assert map_string_double.items().__class__.__name__ == "ItemsView"
 
     keys_type = type(map_string_double.keys())
     assert type(unordered_map_string_double.keys()) is keys_type
@@ -336,6 +336,30 @@ def test_map_view_types():
     assert type(map_string_double_const.items()) is items_type
     assert type(unordered_map_string_double_const.items()) is items_type
 
+    map_string_float = m.MapStringFloat()
+    unordered_map_string_float = m.UnorderedMapStringFloat()
+
+    assert type(map_string_float.keys()) is keys_type
+    assert type(unordered_map_string_float.keys()) is keys_type
+    assert type(map_string_float.values()) is values_type
+    assert type(unordered_map_string_float.values()) is values_type
+    assert type(map_string_float.items()) is items_type
+    assert type(unordered_map_string_float.items()) is items_type
+
+    map_pair_double_int_int32 = m.MapPairDoubleIntInt32()
+    map_pair_double_int_int64 = m.MapPairDoubleIntInt64()
+
+    assert type(map_pair_double_int_int32.values()) is values_type
+    assert type(map_pair_double_int_int64.values()) is values_type
+
+    map_int_object = m.MapIntObject()
+    map_string_object = m.MapStringObject()
+
+    assert type(map_int_object.keys()) is keys_type
+    assert type(map_string_object.keys()) is keys_type
+    assert type(map_int_object.items()) is items_type
+    assert type(map_string_object.items()) is items_type
+
 
 def test_recursive_vector():
     recursive_vector = m.RecursiveVector()

tools/pybind11Common.cmake

@@ -173,12 +173,16 @@ endif()
 # Check to see which Python mode we are in, new, old, or no python
 if(PYBIND11_NOPYTHON)
   set(_pybind11_nopython ON)
+  # We won't use new FindPython if PYBIND11_FINDPYTHON is defined and falselike
+  # Otherwise, we use if FindPythonLibs is missing or if FindPython was already used
 elseif(
-  _pybind11_missing_old_python STREQUAL "NEW"
+  (NOT DEFINED PYBIND11_FINDPYTHON OR PYBIND11_FINDPYTHON)
+  AND (_pybind11_missing_old_python STREQUAL "NEW"
        OR PYBIND11_FINDPYTHON
        OR Python_FOUND
-  OR Python2_FOUND
+       OR Python3_FOUND
-  OR Python3_FOUND)
+      ))
+
   # New mode
   include("${CMAKE_CURRENT_LIST_DIR}/pybind11NewTools.cmake")
 

tools/pybind11NewTools.cmake

@@ -110,14 +110,16 @@ if(NOT DEFINED ${_Python}_EXECUTABLE)
 
 endif()
 
-if(NOT ${_Python}_EXECUTABLE STREQUAL PYBIND11_PYTHON_EXECUTABLE_LAST)
+if(DEFINED PYBIND11_PYTHON_EXECUTABLE_LAST AND NOT ${_Python}_EXECUTABLE STREQUAL
+                                               PYBIND11_PYTHON_EXECUTABLE_LAST)
   # Detect changes to the Python version/binary in subsequent CMake runs, and refresh config if needed
   unset(PYTHON_IS_DEBUG CACHE)
   unset(PYTHON_MODULE_EXTENSION CACHE)
-  set(PYBIND11_PYTHON_EXECUTABLE_LAST
+endif()
+
+set(PYBIND11_PYTHON_EXECUTABLE_LAST
     "${${_Python}_EXECUTABLE}"
     CACHE INTERNAL "Python executable during the last CMake run")
-endif()
 
 if(NOT DEFINED PYTHON_IS_DEBUG)
   # Debug check - see https://stackoverflow.com/questions/646518/python-how-to-detect-debug-Interpreter