Merge branch 'master' into python_multiple_inheritance_test

.pre-commit-config.yaml

@@ -31,7 +31,7 @@ repos:
     types_or: [c++, c, cuda]
 
 # Black, the code formatter, natively supports pre-commit
-- repo: https://github.com/psf/black
+- repo: https://github.com/psf/black-pre-commit-mirror
   rev: "23.7.0" # Keep in sync with blacken-docs
   hooks:
   - id: black

.readthedocs.yml

@@ -1,3 +1,20 @@
+# https://blog.readthedocs.com/migrate-configuration-v2/
+
+version: 2
+
+build:
+  os: ubuntu-22.04
+  apt_packages:
+    - librsvg2-bin
+  tools:
+    python: "3.11"
+
+sphinx:
+  configuration: docs/conf.py
+
 python:
-  version: 3
-requirements_file: docs/requirements.txt
+  install:
+  - requirements: docs/requirements.txt
+
+formats:
+  - pdf

docs/advanced/exceptions.rst

@@ -127,8 +127,7 @@ before a global translator is tried.
 Inside the translator, ``std::rethrow_exception`` should be used within
 a try block to re-throw the exception.  One or more catch clauses to catch
 the appropriate exceptions should then be used with each clause using
-``PyErr_SetString`` to set a Python exception or ``ex(string)`` to set
-the python exception to a custom exception type (see below).
+``py::set_error()`` (see below).
 
 To declare a custom Python exception type, declare a ``py::exception`` variable
 and use this in the associated exception translator (note: it is often useful
@@ -142,14 +141,17 @@ standard python RuntimeError:
 
 .. code-block:: cpp
 
-    static py::exception<MyCustomException> exc(m, "MyCustomError");
+    // This is a static object, so we must leak the Python reference:
+    // It is undefined when the destructor will run, possibly only after the
+    // Python interpreter is finalized already.
+    static py::handle exc = py::exception<MyCustomException>(m, "MyCustomError").release();
     py::register_exception_translator([](std::exception_ptr p) {
         try {
             if (p) std::rethrow_exception(p);
         } catch (const MyCustomException &e) {
-            exc(e.what());
+            py::set_error(exc, e.what());
         } catch (const OtherException &e) {
-            PyErr_SetString(PyExc_RuntimeError, e.what());
+            py::set_error(PyExc_RuntimeError, e.what());
         }
     });
 
@@ -168,8 +170,7 @@ section.
 
 .. note::
 
-    Call either ``PyErr_SetString`` or a custom exception's call
-    operator (``exc(string)``) for every exception caught in a custom exception
+    Call ``py::set_error()`` for every exception caught in a custom exception
     translator.  Failure to do so will cause Python to crash with ``SystemError:
     error return without exception set``.
 
@@ -200,7 +201,7 @@ If module1 has the following translator:
         try {
             if (p) std::rethrow_exception(p);
         } catch (const std::invalid_argument &e) {
-            PyErr_SetString("module1 handled this")
+            py::set_error(PyExc_ArgumentError, "module1 handled this");
         }
       }
 
@@ -212,7 +213,7 @@ and module2 has the following similar translator:
         try {
             if (p) std::rethrow_exception(p);
         } catch (const std::invalid_argument &e) {
-            PyErr_SetString("module2 handled this")
+            py::set_error(PyExc_ArgumentError, "module2 handled this");
         }
       }
 
@@ -312,11 +313,11 @@ error protocol, which is outlined here.
 After calling the Python C API, if Python returns an error,
 ``throw py::error_already_set();``, which allows pybind11 to deal with the
 exception and pass it back to the Python interpreter. This includes calls to
-the error setting functions such as ``PyErr_SetString``.
+the error setting functions such as ``py::set_error()``.
 
 .. code-block:: cpp
 
-    PyErr_SetString(PyExc_TypeError, "C API type error demo");
+    py::set_error(PyExc_TypeError, "C API type error demo");
     throw py::error_already_set();
 
     // But it would be easier to simply...

docs/advanced/functions.rst

@@ -16,7 +16,7 @@ lifetime of objects managed by them. This can lead to issues when creating
 bindings for functions that return a non-trivial type. Just by looking at the
 type information, it is not clear whether Python should take charge of the
 returned value and eventually free its resources, or if this is handled on the
-C++ side. For this reason, pybind11 provides a several *return value policy*
+C++ side. For this reason, pybind11 provides several *return value policy*
 annotations that can be passed to the :func:`module_::def` and
 :func:`class_::def` functions. The default policy is
 :enum:`return_value_policy::automatic`.

include/pybind11/detail/class.h

@@ -373,7 +373,7 @@ extern "C" inline PyObject *pybind11_object_new(PyTypeObject *type, PyObject *,
 extern "C" inline int pybind11_object_init(PyObject *self, PyObject *, PyObject *) {
     PyTypeObject *type = Py_TYPE(self);
     std::string msg = get_fully_qualified_tp_name(type) + ": No constructor defined!";
-    PyErr_SetString(PyExc_TypeError, msg.c_str());
+    set_error(PyExc_TypeError, msg.c_str());
     return -1;
 }
 
@@ -577,7 +577,7 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
         if (view) {
             view->obj = nullptr;
         }
-        PyErr_SetString(PyExc_BufferError, "pybind11_getbuffer(): Internal error");
+        set_error(PyExc_BufferError, "pybind11_getbuffer(): Internal error");
         return -1;
     }
     std::memset(view, 0, sizeof(Py_buffer));
@@ -585,7 +585,7 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
     if ((flags & PyBUF_WRITABLE) == PyBUF_WRITABLE && info->readonly) {
         delete info;
         // view->obj = nullptr;  // Was just memset to 0, so not necessary
-        PyErr_SetString(PyExc_BufferError, "Writable buffer requested for readonly storage");
+        set_error(PyExc_BufferError, "Writable buffer requested for readonly storage");
         return -1;
     }
     view->obj = obj;

include/pybind11/detail/common.h

@@ -399,7 +399,7 @@ PYBIND11_WARNING_POP
         return nullptr;                                                                           \
     }                                                                                             \
     catch (const std::exception &e) {                                                             \
-        PyErr_SetString(PyExc_ImportError, e.what());                                             \
+        ::pybind11::set_error(PyExc_ImportError, e.what());                                       \
         return nullptr;                                                                           \
     }
 

include/pybind11/detail/internals.h

@@ -352,7 +352,7 @@ inline bool raise_err(PyObject *exc_type, const char *msg) {
         raise_from(exc_type, msg);
         return true;
     }
-    PyErr_SetString(exc_type, msg);
+    set_error(exc_type, msg);
     return false;
 }
 

include/pybind11/detail/type_caster_base.h

@@ -821,7 +821,7 @@ public:
         std::string tname = rtti_type ? rtti_type->name() : cast_type.name();
         detail::clean_type_id(tname);
         std::string msg = "Unregistered type : " + tname;
-        PyErr_SetString(PyExc_TypeError, msg.c_str());
+        set_error(PyExc_TypeError, msg.c_str());
         return {nullptr, nullptr};
     }
 

include/pybind11/numpy.h

@@ -1008,7 +1008,7 @@ protected:
     /// Create array from any object -- always returns a new reference
     static PyObject *raw_array(PyObject *ptr, int ExtraFlags = 0) {
         if (ptr == nullptr) {
-            PyErr_SetString(PyExc_ValueError, "cannot create a pybind11::array from a nullptr");
+            set_error(PyExc_ValueError, "cannot create a pybind11::array from a nullptr");
             return nullptr;
         }
         return detail::npy_api::get().PyArray_FromAny_(
@@ -1155,7 +1155,7 @@ protected:
     /// Create array from any object -- always returns a new reference
     static PyObject *raw_array_t(PyObject *ptr) {
         if (ptr == nullptr) {
-            PyErr_SetString(PyExc_ValueError, "cannot create a pybind11::array_t from a nullptr");
+            set_error(PyExc_ValueError, "cannot create a pybind11::array_t from a nullptr");
             return nullptr;
         }
         return detail::npy_api::get().PyArray_FromAny_(ptr,

include/pybind11/pybind11.h

@@ -52,6 +52,45 @@ PYBIND11_WARNING_DISABLE_MSVC(4127)
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
+inline std::string replace_newlines_and_squash(const char *text) {
+    const char *whitespaces = " \t\n\r\f\v";
+    std::string result(text);
+    bool previous_is_whitespace = false;
+
+    // Do not modify string representations
+    char first_char = result[0];
+    char last_char = result[result.size() - 1];
+    if (first_char == last_char && first_char == '\'') {
+        return result;
+    }
+    result.clear();
+
+    // Replace characters in whitespaces array with spaces and squash consecutive spaces
+    while (*text != '\0') {
+        if (std::strchr(whitespaces, *text)) {
+            if (!previous_is_whitespace) {
+                result += ' ';
+                previous_is_whitespace = true;
+            }
+        } else {
+            result += *text;
+            previous_is_whitespace = false;
+        }
+        ++text;
+    }
+
+    // Strip leading and trailing whitespaces
+    const size_t str_begin = result.find_first_not_of(whitespaces);
+    if (str_begin == std::string::npos) {
+        return "";
+    }
+
+    const size_t str_end = result.find_last_not_of(whitespaces);
+    const size_t str_range = str_end - str_begin + 1;
+
+    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
@@ -424,7 +463,7 @@ protected:
                 // Write default value if available.
                 if (!is_starred && arg_index < rec->args.size() && rec->args[arg_index].descr) {
                     signature += " = ";
-                    signature += rec->args[arg_index].descr;
+                    signature += detail::replace_newlines_and_squash(rec->args[arg_index].descr);
                 }
                 // Separator for positional-only arguments (placed after the
                 // argument, rather than before like *
@@ -694,9 +733,8 @@ protected:
         if (overloads->is_constructor) {
             if (!parent
                 || !PyObject_TypeCheck(parent.ptr(), (PyTypeObject *) overloads->scope.ptr())) {
-                PyErr_SetString(
-                    PyExc_TypeError,
-                    "__init__(self, ...) called with invalid or missing `self` argument");
+                set_error(PyExc_TypeError,
+                          "__init__(self, ...) called with invalid or missing `self` argument");
                 return nullptr;
             }
 
@@ -1007,7 +1045,7 @@ protected:
 
                A translator may choose to do one of the following:
 
-                - catch the exception and call PyErr_SetString or PyErr_SetObject
+                - 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.
@@ -1023,8 +1061,7 @@ protected:
                 return nullptr;
             }
 
-            PyErr_SetString(PyExc_SystemError,
-                            "Exception escaped from default exception translator!");
+            set_error(PyExc_SystemError, "Exception escaped from default exception translator!");
             return nullptr;
         }
 
@@ -1125,7 +1162,7 @@ protected:
                 raise_from(PyExc_TypeError, msg.c_str());
                 return nullptr;
             }
-            PyErr_SetString(PyExc_TypeError, msg.c_str());
+            set_error(PyExc_TypeError, msg.c_str());
             return nullptr;
         }
         if (!result) {
@@ -1138,7 +1175,7 @@ protected:
                 raise_from(PyExc_TypeError, msg.c_str());
                 return nullptr;
             }
-            PyErr_SetString(PyExc_TypeError, msg.c_str());
+            set_error(PyExc_TypeError, msg.c_str());
             return nullptr;
         }
         if (overloads->is_constructor && !self_value_and_holder.holder_constructed()) {
@@ -2528,7 +2565,7 @@ inline void register_local_exception_translator(ExceptionTranslator &&translator
 /**
  * Wrapper to generate a new Python exception type.
  *
- * This should only be used with PyErr_SetString for now.
+ * This should only be used with py::set_error() for now.
  * It is not (yet) possible to use as a py::base.
  * Template type argument is reserved for future use.
  */
@@ -2549,7 +2586,9 @@ public:
     }
 
     // Sets the current python exception to this exception object with the given message
-    void operator()(const char *message) { PyErr_SetString(m_ptr, message); }
+    PYBIND11_DEPRECATED("Please use py::set_error() instead "
+                        "(https://github.com/pybind/pybind11/pull/4772)")
+    void operator()(const char *message) const { set_error(*this, message); }
 };
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -2581,7 +2620,7 @@ register_exception_impl(handle scope, const char *name, handle base, bool isLoca
         try {
             std::rethrow_exception(p);
         } catch (const CppException &e) {
-            detail::get_exception_object<CppException>()(e.what());
+            set_error(detail::get_exception_object<CppException>(), e.what());
         }
     });
     return ex;

include/pybind11/pytypes.h

@@ -334,6 +334,14 @@ public:
 #endif
 };
 
+inline void set_error(const handle &type, const char *message) {
+    PyErr_SetString(type.ptr(), message);
+}
+
+inline void set_error(const handle &type, const handle &value) {
+    PyErr_SetObject(type.ptr(), value.ptr());
+}
+
 /** \rst
     Holds a reference to a Python object (with reference counting)
 

tests/cross_module_interleaved_error_already_set.cpp

@@ -16,12 +16,12 @@ namespace {
 namespace py = pybind11;
 
 void interleaved_error_already_set() {
-    PyErr_SetString(PyExc_RuntimeError, "1st error.");
+    py::set_error(PyExc_RuntimeError, "1st error.");
     try {
         throw py::error_already_set();
     } catch (const py::error_already_set &) {
         // The 2nd error could be conditional in a real application.
-        PyErr_SetString(PyExc_RuntimeError, "2nd error.");
+        py::set_error(PyExc_RuntimeError, "2nd error.");
     } // Here the 1st error is destroyed before the 2nd error is fetched.
     // The error_already_set dtor triggers a pybind11::detail::get_internals()
     // call via pybind11::gil_scoped_acquire.

tests/pybind11_cross_module_tests.cpp

@@ -31,11 +31,11 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
     // test_exceptions.py
     py::register_local_exception<LocalSimpleException>(m, "LocalSimpleException");
     m.def("raise_runtime_error", []() {
-        PyErr_SetString(PyExc_RuntimeError, "My runtime error");
+        py::set_error(PyExc_RuntimeError, "My runtime error");
         throw py::error_already_set();
     });
     m.def("raise_value_error", []() {
-        PyErr_SetString(PyExc_ValueError, "My value error");
+        py::set_error(PyExc_ValueError, "My value error");
         throw py::error_already_set();
     });
     m.def("throw_pybind_value_error", []() { throw py::value_error("pybind11 value error"); });
@@ -49,7 +49,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
                 std::rethrow_exception(p);
             }
         } catch (const shared_exception &e) {
-            PyErr_SetString(PyExc_KeyError, e.what());
+            py::set_error(PyExc_KeyError, e.what());
         }
     });
 
@@ -60,7 +60,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) {
                 std::rethrow_exception(p);
             }
         } catch (const LocalException &e) {
-            PyErr_SetString(PyExc_KeyError, e.what());
+            py::set_error(PyExc_KeyError, e.what());
         }
     });
 

tests/test_eigen_matrix.cpp

@@ -330,6 +330,23 @@ TEST_SUBMODULE(eigen_matrix, m) {
     m.def("dense_c", [mat]() -> DenseMatrixC { return DenseMatrixC(mat); });
     m.def("dense_copy_r", [](const DenseMatrixR &m) -> DenseMatrixR { return m; });
     m.def("dense_copy_c", [](const DenseMatrixC &m) -> DenseMatrixC { return m; });
+    // test_defaults
+    bool have_numpy = true;
+    try {
+        py::module_::import("numpy");
+    } catch (const py::error_already_set &) {
+        have_numpy = false;
+    }
+    if (have_numpy) {
+        py::module_::import("numpy");
+        Eigen::Matrix<double, 3, 3> defaultMatrix = Eigen::Matrix3d::Identity();
+        m.def(
+            "defaults_mat", [](const Eigen::Matrix3d &) {}, py::arg("mat") = defaultMatrix);
+
+        Eigen::VectorXd defaultVector = Eigen::VectorXd::Ones(32);
+        m.def(
+            "defaults_vec", [](const Eigen::VectorXd &) {}, py::arg("vec") = defaultMatrix);
+    }
     // test_sparse, test_sparse_signature
     m.def("sparse_r", [mat]() -> SparseMatrixR {
         // NOLINTNEXTLINE(clang-analyzer-core.uninitialized.UndefReturn)

tests/test_eigen_matrix.py

@@ -716,6 +716,11 @@ def test_dense_signature(doc):
     )
 
 
+def test_defaults(doc):
+    assert "\n" not in str(doc(m.defaults_mat))
+    assert "\n" not in str(doc(m.defaults_vec))
+
+
 def test_named_arguments():
     a = np.array([[1.0, 2], [3, 4], [5, 6]])
     b = np.ones((2, 1))

tests/test_exceptions.cpp

@@ -25,6 +25,10 @@ private:
     std::string message = "";
 };
 
+class MyExceptionUseDeprecatedOperatorCall : public MyException {
+    using MyException::MyException;
+};
+
 // A type that should be translated to a standard Python exception
 class MyException2 : public std::exception {
 public:
@@ -109,8 +113,8 @@ TEST_SUBMODULE(exceptions, m) {
     m.def("throw_std_exception",
           []() { throw std::runtime_error("This exception was intentionally thrown."); });
 
-    // make a new custom exception and use it as a translation target
-    static py::exception<MyException> ex(m, "MyException");
+    // PLEASE KEEP IN SYNC with docs/advanced/exceptions.rst
+    static py::handle ex = py::exception<MyException>(m, "MyException").release();
     py::register_exception_translator([](std::exception_ptr p) {
         try {
             if (p) {
@@ -118,7 +122,32 @@ TEST_SUBMODULE(exceptions, m) {
             }
         } catch (const MyException &e) {
             // Set MyException as the active python error
-            ex(e.what());
+            py::set_error(ex, e.what());
+        }
+    });
+
+    // Same as above, but using the deprecated `py::exception<>::operator()`
+    // We want to be sure it still works, until it's removed.
+    static const auto *const exd = new py::exception<MyExceptionUseDeprecatedOperatorCall>(
+        m, "MyExceptionUseDeprecatedOperatorCall");
+    py::register_exception_translator([](std::exception_ptr p) {
+        try {
+            if (p) {
+                std::rethrow_exception(p);
+            }
+        } catch (const MyExceptionUseDeprecatedOperatorCall &e) {
+#if defined(__INTEL_COMPILER) || defined(__NVCOMPILER)
+            // It is not worth the trouble dealing with warning suppressions for these compilers.
+            // Falling back to the recommended approach to keep the test code simple.
+            py::set_error(*exd, e.what());
+#else
+            PYBIND11_WARNING_PUSH
+            PYBIND11_WARNING_DISABLE_CLANG("-Wdeprecated-declarations")
+            PYBIND11_WARNING_DISABLE_GCC("-Wdeprecated-declarations")
+            PYBIND11_WARNING_DISABLE_MSVC(4996)
+            (*exd)(e.what());
+            PYBIND11_WARNING_POP
+#endif
         }
     });
 
@@ -132,7 +161,7 @@ TEST_SUBMODULE(exceptions, m) {
             }
         } catch (const MyException2 &e) {
             // Translate this exception to a standard RuntimeError
-            PyErr_SetString(PyExc_RuntimeError, e.what());
+            py::set_error(PyExc_RuntimeError, e.what());
         }
     });
 
@@ -162,11 +191,16 @@ TEST_SUBMODULE(exceptions, m) {
                 std::rethrow_exception(p);
             }
         } catch (const MyException6 &e) {
-            PyErr_SetString(PyExc_RuntimeError, e.what());
+            py::set_error(PyExc_RuntimeError, e.what());
         }
     });
 
-    m.def("throws1", []() { throw MyException("this error should go to a custom type"); });
+    m.def("throws1",
+          []() { throw MyException("this error should go to py::exception<MyException>"); });
+    m.def("throws1d", []() {
+        throw MyExceptionUseDeprecatedOperatorCall(
+            "this error should go to py::exception<MyExceptionUseDeprecatedOperatorCall>");
+    });
     m.def("throws2",
           []() { throw MyException2("this error should go to a standard Python exception"); });
     m.def("throws3", []() { throw MyException3("this error cannot be translated"); });
@@ -222,7 +256,7 @@ TEST_SUBMODULE(exceptions, m) {
 
     m.def("throw_already_set", [](bool err) {
         if (err) {
-            PyErr_SetString(PyExc_ValueError, "foo");
+            py::set_error(PyExc_ValueError, "foo");
         }
         try {
             throw py::error_already_set();
@@ -238,7 +272,7 @@ TEST_SUBMODULE(exceptions, m) {
         }
         PyErr_Clear();
         if (err) {
-            PyErr_SetString(PyExc_ValueError, "foo");
+            py::set_error(PyExc_ValueError, "foo");
         }
         throw py::error_already_set();
     });
@@ -247,7 +281,7 @@ TEST_SUBMODULE(exceptions, m) {
         bool retval = false;
         try {
             PythonCallInDestructor set_dict_in_destructor(d);
-            PyErr_SetString(PyExc_ValueError, "foo");
+            py::set_error(PyExc_ValueError, "foo");
             throw py::error_already_set();
         } catch (const py::error_already_set &) {
             retval = true;
@@ -282,14 +316,14 @@ TEST_SUBMODULE(exceptions, m) {
     m.def("throw_should_be_translated_to_key_error", []() { throw shared_exception(); });
 
     m.def("raise_from", []() {
-        PyErr_SetString(PyExc_ValueError, "inner");
+        py::set_error(PyExc_ValueError, "inner");
         py::raise_from(PyExc_ValueError, "outer");
         throw py::error_already_set();
     });
 
     m.def("raise_from_already_set", []() {
         try {
-            PyErr_SetString(PyExc_ValueError, "inner");
+            py::set_error(PyExc_ValueError, "inner");
             throw py::error_already_set();
         } catch (py::error_already_set &e) {
             py::raise_from(e, PyExc_ValueError, "outer");
@@ -306,7 +340,7 @@ TEST_SUBMODULE(exceptions, m) {
     });
 
     m.def("error_already_set_what", [](const py::object &exc_type, const py::object &exc_value) {
-        PyErr_SetObject(exc_type.ptr(), exc_value.ptr());
+        py::set_error(exc_type, exc_value);
         std::string what = py::error_already_set().what();
         bool py_err_set_after_what = (PyErr_Occurred() != nullptr);
         PyErr_Clear();
@@ -321,7 +355,7 @@ TEST_SUBMODULE(exceptions, m) {
     });
 
     m.def("test_error_already_set_double_restore", [](bool dry_run) {
-        PyErr_SetString(PyExc_ValueError, "Random error.");
+        py::set_error(PyExc_ValueError, "Random error.");
         py::error_already_set e;
         e.restore();
         PyErr_Clear();

tests/test_exceptions.h

@@ -9,5 +9,5 @@ class PYBIND11_EXPORT_EXCEPTION shared_exception : public pybind11::builtin_exce
 public:
     using builtin_exception::builtin_exception;
     explicit shared_exception() : shared_exception("") {}
-    void set_error() const override { PyErr_SetString(PyExc_RuntimeError, what()); }
+    void set_error() const override { py::set_error(PyExc_RuntimeError, what()); }
 };

tests/test_exceptions.py

@@ -139,7 +139,15 @@ def test_custom(msg):
     # Can we catch a MyException?
     with pytest.raises(m.MyException) as excinfo:
         m.throws1()
-    assert msg(excinfo.value) == "this error should go to a custom type"
+    assert msg(excinfo.value) == "this error should go to py::exception<MyException>"
+
+    # Can we catch a MyExceptionUseDeprecatedOperatorCall?
+    with pytest.raises(m.MyExceptionUseDeprecatedOperatorCall) as excinfo:
+        m.throws1d()
+    assert (
+        msg(excinfo.value)
+        == "this error should go to py::exception<MyExceptionUseDeprecatedOperatorCall>"
+    )
 
     # Can we translate to standard Python exceptions?
     with pytest.raises(RuntimeError) as excinfo:

tests/test_kwargs_and_defaults.cpp

@@ -42,6 +42,50 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     m.def("kw_func_udl", kw_func, "x"_a, "y"_a = 300);
     m.def("kw_func_udl_z", kw_func, "x"_a, "y"_a = 0);
 
+    // test line breaks in default argument representation
+    struct CustomRepr {
+        std::string repr_string;
+
+        explicit CustomRepr(const std::string &repr) : repr_string(repr) {}
+
+        std::string __repr__() const { return repr_string; }
+    };
+
+    py::class_<CustomRepr>(m, "CustomRepr")
+        .def(py::init<const std::string &>())
+        .def("__repr__", &CustomRepr::__repr__);
+
+    m.def(
+        "kw_lb_func0",
+        [](const CustomRepr &) {},
+        py::arg("custom") = CustomRepr("  array([[A, B], [C, D]])  "));
+    m.def(
+        "kw_lb_func1",
+        [](const CustomRepr &) {},
+        py::arg("custom") = CustomRepr("  array([[A, B],\n[C, D]])  "));
+    m.def(
+        "kw_lb_func2",
+        [](const CustomRepr &) {},
+        py::arg("custom") = CustomRepr("\v\n   array([[A, B], [C, D]])"));
+    m.def(
+        "kw_lb_func3",
+        [](const CustomRepr &) {},
+        py::arg("custom") = CustomRepr("array([[A, B], [C, D]])   \f\n"));
+    m.def(
+        "kw_lb_func4",
+        [](const CustomRepr &) {},
+        py::arg("custom") = CustomRepr("array([[A, B],\n\f\n[C, D]])"));
+    m.def(
+        "kw_lb_func5",
+        [](const CustomRepr &) {},
+        py::arg("custom") = CustomRepr("array([[A, B],\r  [C, D]])"));
+    m.def(
+        "kw_lb_func6", [](const CustomRepr &) {}, py::arg("custom") = CustomRepr(" \v\t "));
+    m.def(
+        "kw_lb_func7",
+        [](const std::string &) {},
+        py::arg("str_arg") = "First line.\n  Second line.");
+
     // test_args_and_kwargs
     m.def("args_function", [](py::args args) -> py::tuple {
         PYBIND11_WARNING_PUSH

tests/test_kwargs_and_defaults.py

@@ -23,6 +23,38 @@ def test_function_signatures(doc):
         doc(m.KWClass.foo1)
         == "foo1(self: m.kwargs_and_defaults.KWClass, x: int, y: float) -> None"
     )
+    assert (
+        doc(m.kw_lb_func0)
+        == "kw_lb_func0(custom: m.kwargs_and_defaults.CustomRepr = array([[A, B], [C, D]])) -> None"
+    )
+    assert (
+        doc(m.kw_lb_func1)
+        == "kw_lb_func1(custom: m.kwargs_and_defaults.CustomRepr = array([[A, B], [C, D]])) -> None"
+    )
+    assert (
+        doc(m.kw_lb_func2)
+        == "kw_lb_func2(custom: m.kwargs_and_defaults.CustomRepr = array([[A, B], [C, D]])) -> None"
+    )
+    assert (
+        doc(m.kw_lb_func3)
+        == "kw_lb_func3(custom: m.kwargs_and_defaults.CustomRepr = array([[A, B], [C, D]])) -> None"
+    )
+    assert (
+        doc(m.kw_lb_func4)
+        == "kw_lb_func4(custom: m.kwargs_and_defaults.CustomRepr = array([[A, B], [C, D]])) -> None"
+    )
+    assert (
+        doc(m.kw_lb_func5)
+        == "kw_lb_func5(custom: m.kwargs_and_defaults.CustomRepr = array([[A, B], [C, D]])) -> None"
+    )
+    assert (
+        doc(m.kw_lb_func6)
+        == "kw_lb_func6(custom: m.kwargs_and_defaults.CustomRepr = ) -> None"
+    )
+    assert (
+        doc(m.kw_lb_func7)
+        == "kw_lb_func7(str_arg: str = 'First line.\\n  Second line.') -> None"
+    )
 
 
 def test_named_arguments():

tests/test_pytypes.cpp

@@ -25,7 +25,7 @@ PyObject *conv(PyObject *o) {
             ret = PyFloat_FromDouble(v);
         }
     } else {
-        PyErr_SetString(PyExc_TypeError, "Unexpected type");
+        py::set_error(PyExc_TypeError, "Unexpected type");
     }
     return ret;
 }

tests/test_type_caster_pyobject_ptr.cpp

@@ -78,14 +78,14 @@ TEST_SUBMODULE(type_caster_pyobject_ptr, m) {
 
     m.def("cast_to_pyobject_ptr_nullptr", [](bool set_error) {
         if (set_error) {
-            PyErr_SetString(PyExc_RuntimeError, "Reflective of healthy error handling.");
+            py::set_error(PyExc_RuntimeError, "Reflective of healthy error handling.");
         }
         PyObject *ptr = nullptr;
         py::cast(ptr);
     });
 
     m.def("cast_to_pyobject_ptr_non_nullptr_with_error_set", []() {
-        PyErr_SetString(PyExc_RuntimeError, "Reflective of unhealthy error handling.");
+        py::set_error(PyExc_RuntimeError, "Reflective of unhealthy error handling.");
         py::cast(Py_None);
     });
 

tools/pybind11NewTools.cmake

@@ -233,11 +233,13 @@ function(pybind11_add_module target_name)
     endif()
   endif()
 
-  # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
-  string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
-  if(NOT MSVC AND NOT "${uppercase_CMAKE_BUILD_TYPE}" MATCHES DEBUG|RELWITHDEBINFO)
-    # Strip unnecessary sections of the binary on Linux/macOS
-    pybind11_strip(${target_name})
+  if(DEFINED CMAKE_BUILD_TYPE) # see https://github.com/pybind/pybind11/issues/4454
+    # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
+    string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+    if(NOT MSVC AND NOT "${uppercase_CMAKE_BUILD_TYPE}" MATCHES DEBUG|RELWITHDEBINFO)
+      # Strip unnecessary sections of the binary on Linux/macOS
+      pybind11_strip(${target_name})
+    endif()
   endif()
 
   if(MSVC)

tools/pybind11Tools.cmake

@@ -212,10 +212,12 @@ function(pybind11_add_module target_name)
     endif()
   endif()
 
-  # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
-  string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
-  if(NOT MSVC AND NOT "${uppercase_CMAKE_BUILD_TYPE}" MATCHES DEBUG|RELWITHDEBINFO)
-    pybind11_strip(${target_name})
+  if(DEFINED CMAKE_BUILD_TYPE) # see https://github.com/pybind/pybind11/issues/4454
+    # Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
+    string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
+    if(NOT MSVC AND NOT "${uppercase_CMAKE_BUILD_TYPE}" MATCHES DEBUG|RELWITHDEBINFO)
+      pybind11_strip(${target_name})
+    endif()
   endif()
 
   if(MSVC)