Merge branch 'pybind:master' into master

.github/workflows/ci.yml

@@ -501,7 +501,9 @@ jobs:
           - { gcc: 7, std: 17 }
           - { gcc: 8, std: 14 }
           - { gcc: 8, std: 17 }
+          - { gcc: 9, std: 20 }
           - { gcc: 10, std: 17 }
+          - { gcc: 10, std: 20 }
           - { gcc: 11, std: 20 }
           - { gcc: 12, std: 20 }
           - { gcc: 13, std: 20 }

include/pybind11/cast.h

@@ -740,6 +740,13 @@ class type_caster<std::pair<T1, T2>> : public tuple_caster<std::pair, T1, T2> {}
 template <typename... Ts>
 class type_caster<std::tuple<Ts...>> : public tuple_caster<std::tuple, Ts...> {};
 
+template <>
+class type_caster<std::tuple<>> : public tuple_caster<std::tuple> {
+public:
+    // PEP 484 specifies this syntax for an empty tuple
+    static constexpr auto name = const_name("tuple[()]");
+};
+
 /// Helper class which abstracts away certain actions. Users can provide specializations for
 /// custom holders, but it's only necessary if the type has a non-standard interface.
 template <typename T>

include/pybind11/typing.h

@@ -14,6 +14,8 @@
 #include "cast.h"
 #include "pytypes.h"
 
+#include <algorithm>
+
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(typing)
 
@@ -98,7 +100,10 @@ class Never : public none {
     using none::none;
 };
 
-#if defined(__cpp_nontype_template_parameter_class)
+#if defined(__cpp_nontype_template_parameter_class)                                               \
+    && (/* See #5201 */ !defined(__GNUC__)                                                        \
+        || (__GNUC__ > 10 || (__GNUC__ == 10 && __GNUC_MINOR__ >= 3)))
+#    define PYBIND11_TYPING_H_HAS_STRING_LITERAL
 template <size_t N>
 struct StringLiteral {
     constexpr StringLiteral(const char (&str)[N]) { std::copy_n(str, N, name); }
@@ -222,7 +227,7 @@ struct handle_type_name<typing::Never> {
     static constexpr auto name = const_name("Never");
 };
 
-#if defined(__cpp_nontype_template_parameter_class)
+#if defined(PYBIND11_TYPING_H_HAS_STRING_LITERAL)
 template <typing::StringLiteral... Literals>
 struct handle_type_name<typing::Literal<Literals...>> {
     static constexpr auto name = const_name("Literal[")

tests/test_builtin_casters.py

@@ -368,6 +368,8 @@ def test_tuple(doc):
     """
     )
 
+    assert doc(m.empty_tuple) == """empty_tuple() -> tuple[()]"""
+
     assert m.rvalue_pair() == ("rvalue", "rvalue")
     assert m.lvalue_pair() == ("lvalue", "lvalue")
     assert m.rvalue_tuple() == ("rvalue", "rvalue", "rvalue")

tests/test_pytypes.cpp

@@ -109,7 +109,7 @@ void m_defs(py::module_ &m) {
 
 } // namespace handle_from_move_only_type_with_operator_PyObject
 
-#if defined(__cpp_nontype_template_parameter_class)
+#if defined(PYBIND11_TYPING_H_HAS_STRING_LITERAL)
 namespace literals {
 enum Color { RED = 0, BLUE = 1 };
 
@@ -905,7 +905,7 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("annotate_optional_to_object",
           [](py::typing::Optional<int> &o) -> py::object { return o; });
 
-#if defined(__cpp_nontype_template_parameter_class)
+#if defined(PYBIND11_TYPING_H_HAS_STRING_LITERAL)
     py::enum_<literals::Color>(m, "Color")
         .value("RED", literals::Color::RED)
         .value("BLUE", literals::Color::BLUE);
@@ -919,8 +919,8 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("annotate_listT_to_T",
           [](const py::typing::List<typevar::TypeVarT> &l) -> typevar::TypeVarT { return l[0]; });
     m.def("annotate_object_to_T", [](const py::object &o) -> typevar::TypeVarT { return o; });
-    m.attr("if_defined__cpp_nontype_template_parameter_class") = true;
+    m.attr("defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL") = true;
 #else
-    m.attr("if_defined__cpp_nontype_template_parameter_class") = false;
+    m.attr("defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL") = false;
 #endif
 }

tests/test_pytypes.py

@@ -1025,7 +1025,7 @@ def test_optional_object_annotations(doc):
 
 
 @pytest.mark.skipif(
-    not m.if_defined__cpp_nontype_template_parameter_class,
+    not m.defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL,
     reason="C++20 feature not available.",
 )
 def test_literal(doc):
@@ -1036,7 +1036,7 @@ def test_literal(doc):
 
 
 @pytest.mark.skipif(
-    not m.if_defined__cpp_nontype_template_parameter_class,
+    not m.defined_PYBIND11_TYPING_H_HAS_STRING_LITERAL,
     reason="C++20 feature not available.",
 )
 def test_typevar(doc):

tools/pybind11Common.cmake

@@ -335,7 +335,7 @@ function(_pybind11_generate_lto target prefer_thin_lto)
       set(PYBIND11_LTO_LINKER_FLAGS "-flto${thin}${linker_append}")
     elseif(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
       _pybind11_return_if_cxx_and_linker_flags_work(
-        HAS_FLTO_THIN "-flto${thin}${cxx_append}" "-flto=${thin}${linker_append}"
+        HAS_FLTO_THIN "-flto${thin}${cxx_append}" "-flto${thin}${linker_append}"
         PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
     endif()
     if(NOT HAS_FLTO_THIN)