Add Clang support

doc/pfr.qbk

@@ -478,7 +478,7 @@ struct aggregate : empty { // not a SimpleAggregate
 The library may work with aggregates that don't satisfy the requirements of `SimpleAggregate`, but the behavior tends to be non-portable.
 
 Boost.PFR's extraction of field name works with a `SimpleAggregate` which variables are able to be declared in any other translation unit.
-It's better not to use this feature with anonymous or local structure.
+It's better not to use this feature with anonymous structure, local structure or a structure defined inside anonymous namespace.
 
 ```
 struct external_simple_aggregate {

include/boost/pfr/config.hpp

@@ -107,8 +107,12 @@
 #endif
 
 #ifndef BOOST_PFR_ENABLE_GETTING_NAMES
-#   if defined(__cpp_nontype_template_args) && __cpp_nontype_template_args >= 201911 && BOOST_PFR_FUNCTION_MACRO_SUPPORTED
-#       define BOOST_PFR_ENABLE_GETTING_NAMES 1
+#   if (defined(__cpp_nontype_template_args) && __cpp_nontype_template_args >= 201911) || (__cplusplus >= 202002L && defined(__clang_major__) && __clang_major__ >= 12)
+#       if BOOST_PFR_FUNCTION_MACRO_SUPPORTED
+#          define BOOST_PFR_ENABLE_GETTING_NAMES 1
+#       else
+#          define BOOST_PFR_ENABLE_GETTING_NAMES 0
+#       endif
 #   else
 #       define BOOST_PFR_ENABLE_GETTING_NAMES 0
 #   endif

include/boost/pfr/detail/core_name20_static.hpp

@@ -30,15 +30,15 @@ constexpr auto make_sequence_tuple(Args... args) noexcept {
     return sequence_tuple::tuple<Args...>{ args... };
 }
 
-template <typename MsvcWorkaround, auto* ptr> 
+template <typename MsvcWorkaround, auto ptr> 
 consteval auto name_of_field_impl() noexcept {
 #ifdef _MSC_VER
     constexpr std::string_view sv = __FUNCSIG__;
     // - strlen("(void)") - strlen(" noexcept")
-    constexpr auto last = sv.find_last_not_of(" >(", sv.size() - 6 - 9);
+    constexpr auto last = sv.find_last_not_of(" >(}", sv.size() - 6 - 9);
 #else
     constexpr std::string_view sv = __PRETTY_FUNCTION__;
-    constexpr auto last = sv.find_last_not_of(" ])");
+    constexpr auto last = sv.find_last_not_of(" ])}");
 #endif
     constexpr auto first = sv.find_last_not_of("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_0123456789", last);
     auto res = std::array<char, last - first + 2>{};
@@ -51,11 +51,40 @@ consteval auto name_of_field_impl() noexcept {
 template <typename T>
 extern const T fake_object;
 
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wundefined-var-template"
+
+template<class T>
+struct clang_workaround_t {
+    T v;
+};
+template<class T>
+clang_workaround_t(T) -> clang_workaround_t<T>;
+
+template<typename T>
+constexpr auto clang_workaround(const T& arg) noexcept {
+    return clang_workaround_t{arg};
+}
+
+#else
+
+template<typename T>
+constexpr const T& clang_workaround(const T& arg) noexcept {
+    return arg;
+}
+
+#endif
+
 // Without passing 'T' into 'name_of_field_impl' different fields from different structures might have the same name!
 template <class T, std::size_t I>
-constexpr auto stored_name_of_field = name_of_field_impl<T, &detail::sequence_tuple::get<I>(
+constexpr auto stored_name_of_field = name_of_field_impl<T, clang_workaround(&detail::sequence_tuple::get<I>(
     detail::tie_as_tuple(fake_object<T>) 
-)>();
+))>();
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
 
 template <class T, std::size_t... I>
 constexpr auto tie_as_names_tuple_impl(std::index_sequence<I...>) noexcept {

test/core_name/Jamfile.v2

@@ -12,7 +12,7 @@ import python ;
 import testing ;
 import ../../config/checks/config : requires ;
 
-########## BEGIN of helpers to detect C++20 non-type template args support
+########## BEGIN of helpers to detect C++20 features support
 
 actions mp_simple_run_action
 {
@@ -31,17 +31,16 @@ rule mp-run-simple ( sources + : args * : input-files * : requirements * : targe
 mp-run-simple cxx20_nontype_template_args_detection.cpp : : : : compiler_supports_cxx20_nontype_template_args ;
 explicit compiler_supports_cxx20_nontype_template_args ;
 
-########## END of helpers to detect C++20 non-type template args support
+mp-run-simple cxx20_clang_workaround_detection.cpp : : : : compiler_supports_cxx20_clang_workaround ;
+explicit compiler_supports_cxx20_clang_workaround ;
 
-local REQUIRE_CXX20_NONTYPE_TEMPLATE_ARGS =
-    [ check-target-builds ../core_name//compiler_supports_cxx20_nontype_template_args : : <build>no ]
-  ;
+########## END of helpers to detect C++20 features support
 
 project
     : source-location .
     : requirements
         <define>BOOST_PFR_DETAIL_STRICT_RVALUE_TESTING=1
-        [ check-target-builds ../core_name//compiler_supports_cxx20_nontype_template_args : : <build>no ]
+        [ check-target-builds ../core_name//compiler_supports_cxx20_nontype_template_args : : [ check-target-builds ../core_name//compiler_supports_cxx20_clang_workaround : : <build>no ] ]
     ;
 
 

test/core_name/cxx20_clang_workaround_detection.cpp

@@ -0,0 +1,32 @@
+// Copyright (c) 2023 Bela Schaum, X-Ryl669, Denis Mikhailov.
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+
+// Initial implementation by Bela Schaum, https://github.com/schaumb
+// The way to make it union and UB free by X-Ryl669, https://github.com/X-Ryl669
+//
+
+template <auto p>
+class X {};
+
+template <class T>
+struct Store
+{
+    T v;
+};
+
+template <class T>
+Store(T) -> Store<T>;
+
+struct S
+{
+    int m;
+} s;
+
+X<Store{&s.m}> x4;
+
+int main() {}
+
+

test/core_name/fields_names.cpp

@@ -16,8 +16,6 @@
 
 namespace testing {
 
-namespace {
-
 struct nonconstexpr {
     nonconstexpr() {};
 };
@@ -67,9 +65,6 @@ void test_names_as_array() {
 }
 
 
-} // anonymous namespace
-
-
 } // namespace testing
 
 int main() {

test/core_name/fields_names_nonascii.cpp.tpl

@@ -14,8 +14,6 @@
 
 namespace testing {
 
-namespace {
-
 struct Aggregate {
     int _%ARG%;
 };
@@ -35,8 +33,6 @@ void test_names_as_array() {
     }
 }
 
-} // anonymous namespace
-
 
 } // namespace testing