Make the "Pointer types ... are not supported" message Eigen-specific, as suggested by @Lalaland. Move to new pybind11/eigen/common.h header.

CMakeLists.txt

@@ -126,6 +126,7 @@ set(PYBIND11_HEADERS
     include/pybind11/complex.h
     include/pybind11/options.h
     include/pybind11/eigen.h
+    include/pybind11/eigen/common.h
     include/pybind11/eigen/matrix.h
     include/pybind11/eigen/tensor.h
     include/pybind11/embed.h

include/pybind11/detail/common.h

@@ -1034,11 +1034,6 @@ struct format_descriptor<
     static std::string format() { return std::string(1, c); }
 };
 
-// Common message for `static_assert()`s, which are useful to easily preempt much less obvious
-// errors in code that does not support `format_descriptor<PyObject *>`.
-#define PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED                                          \
-    "Pointer types (in particular `PyObject *`) are not supported."
-
 PYBIND11_NAMESPACE_BEGIN(detail)
 // Returns the index of the given type in the type char array below, and in the list in numpy.h
 // The order here is: bool; 8 ints ((signed,unsigned)x(8,16,32,64)bits); float,double,long double;

include/pybind11/eigen/common.h

@@ -0,0 +1,9 @@
+// Copyright (c) 2023 The pybind Community.
+
+#pragma once
+
+// Common message for `static_assert()`s, which are useful to easily
+// preempt much less obvious errors.
+#define PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED                                    \
+    "Pointer types (in particular `PyObject *`) are not supported as scalar types for Eigen "     \
+    "types."

include/pybind11/eigen/matrix.h

@@ -10,6 +10,7 @@
 #pragma once
 
 #include "../numpy.h"
+#include "common.h"
 
 /* HINT: To suppress warnings originating from the Eigen headers, use -isystem.
    See also:
@@ -288,7 +289,7 @@ template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_dense_plain<Type>::value>> {
     using Scalar = typename Type::Scalar;
     static_assert(!std::is_pointer<Scalar>::value,
-                  PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using props = EigenProps<Type>;
 
     bool load(handle src, bool convert) {
@@ -408,7 +409,7 @@ private:
 template <typename MapType>
 struct eigen_map_caster {
     static_assert(!std::is_pointer<typename MapType::Scalar>::value,
-                  PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
 
 private:
     using props = EigenProps<MapType>;
@@ -463,7 +464,7 @@ private:
     using props = EigenProps<Type>;
     using Scalar = typename props::Scalar;
     static_assert(!std::is_pointer<Scalar>::value,
-                  PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using MapType = Eigen::Map<PlainObjectType, 0, StrideType>;
     using Array
         = array_t<Scalar,
@@ -612,7 +613,7 @@ private:
 template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_other<Type>::value>> {
     static_assert(!std::is_pointer<typename Type::Scalar>::value,
-                  PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
 
 protected:
     using Matrix
@@ -643,7 +644,7 @@ template <typename Type>
 struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
     using Scalar = typename Type::Scalar;
     static_assert(!std::is_pointer<Scalar>::value,
-                  PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using StorageIndex = remove_reference_t<decltype(*std::declval<Type>().outerIndexPtr())>;
     using Index = typename Type::Index;
     static constexpr bool rowMajor = Type::IsRowMajor;

include/pybind11/eigen/tensor.h

@@ -8,6 +8,7 @@
 #pragma once
 
 #include "../numpy.h"
+#include "common.h"
 
 #if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
 static_assert(__GNUC__ > 5, "Eigen Tensor support in pybind11 requires GCC > 5.0");
@@ -165,7 +166,7 @@ PYBIND11_WARNING_POP
 template <typename Type>
 struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
     static_assert(!std::is_pointer<typename Type::Scalar>::value,
-                  PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using Helper = eigen_tensor_helper<Type>;
     static constexpr auto temp_name = get_tensor_descriptor<Type, false>::value;
     PYBIND11_TYPE_CASTER(Type, temp_name);
@@ -362,7 +363,7 @@ template <typename Type, int Options>
 struct type_caster<Eigen::TensorMap<Type, Options>,
                    typename eigen_tensor_helper<remove_cv_t<Type>>::ValidType> {
     static_assert(!std::is_pointer<typename Type::Scalar>::value,
-                  PYBIND11_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
+                  PYBIND11_EIGEN_MESSAGE_POINTER_TYPES_ARE_NOT_SUPPORTED);
     using MapType = Eigen::TensorMap<Type, Options>;
     using Helper = eigen_tensor_helper<remove_cv_t<Type>>;
 

tests/extra_python_package/test_files.py

@@ -57,6 +57,7 @@ detail_headers = {
 }
 
 eigen_headers = {
+    "include/pybind11/eigen/common.h",
     "include/pybind11/eigen/matrix.h",
     "include/pybind11/eigen/tensor.h",
 }