Parsing ala boost type_index

include/boost/pfr/detail/core_name14_disabled.hpp

@@ -21,7 +21,7 @@ template <class T, std::size_t I>
 constexpr auto get_name() noexcept {
     static_assert(
         sizeof(T) && false,
-        "====================> Boost.PFR: Field's names extracting functionality requires C++20 and compiler that supports __PRETTY_FUNCTION__ or __FUNCSIG__ macro (GCC, Clang or MSVC)."
+        "====================> Boost.PFR: Field's names extracting functionality requires C++20."
     );
 
     return nullptr;
@@ -31,7 +31,7 @@ template <class T>
 constexpr auto tie_as_names_tuple() noexcept {
     static_assert(
         sizeof(T) && false,
-        "====================> Boost.PFR: Field's names extracting functionality requires C++20 and compiler that supports __PRETTY_FUNCTION__ or __FUNCSIG__ macro (GCC, Clang or MSVC)."
+        "====================> Boost.PFR: Field's names extracting functionality requires C++20."
     );
 
     return detail::sequence_tuple::make_sequence_tuple();

include/boost/pfr/detail/core_name20_static.hpp

@@ -24,30 +24,96 @@
 
 namespace boost { namespace pfr { namespace detail {
 
-consteval std::string_view name_of_field_parse(std::string_view sv,
-                                               std::size_t size_at_begin,
-                                               std::size_t size_at_end,
-                                               std::string_view until_runtime_last) noexcept {
-    sv.remove_prefix(size_at_begin);
-    sv.remove_suffix(size_at_end);
-    return sv.substr(sv.rfind(until_runtime_last) + until_runtime_last.size());
+struct core_name_skip {
+    std::size_t size_at_begin;
+    std::size_t size_at_end;
+    bool more_at_runtime;
+    std::string_view until_runtime_last;
+};
+
+consteval core_name_skip make_core_name_skip(std::size_t size_at_begin,
+                                             std::size_t size_at_end,
+                                             bool more_at_runtime,
+                                             std::string_view until_runtime_last) noexcept
+{
+    return core_name_skip{size_at_begin, size_at_end, more_at_runtime, until_runtime_last};
 }
 
-template <typename MsvcWorkaround, auto ptr>
-consteval auto name_of_field_impl() noexcept {
-#ifdef _MSC_VER
-    constexpr auto sv = __FUNCSIG__;
+consteval core_name_skip make_core_name_skip(std::size_t size_at_begin,
+                                             std::size_t size_at_end,
+                                             std::string_view until_runtime_last) noexcept
+{
+    return core_name_skip{size_at_begin, size_at_end, true, until_runtime_last};
+}
+
+consteval std::string_view apply_core_name_skip(std::string_view sv,
+                                                core_name_skip s) noexcept {
+    sv.remove_prefix((std::min)(s.size_at_begin, sv.size()));
+    sv.remove_suffix((std::min)(s.size_at_end, sv.size()));
+    return s.more_at_runtime ? sv.substr((std::min)(sv.rfind(s.until_runtime_last) + s.until_runtime_last.size(), sv.size()))
+                             : sv;
+                             ;
+}
+
+template <bool Condition>
+consteval void assert_compile_time_legths() noexcept {
+    static_assert(
+        Condition,
+        "PFRs extraction of field name is misconfigured for your compiler. "
+        "Please define BOOST_PFR_CORE_NAME_USER_DEFINED_PARSING to correct values. See section "
+        "'TODO: name of the section' of the documentation for more information."
+    );
+}
+
+template <class T>
+consteval void failed_to_get_function_name() noexcept {
+    static_assert(
+        sizeof(T) && false,
+        "PFRs extraction of field name could not detect your compiler. "
+        "Please make the BOOST_PFR_FUNCTION_SIGNATURE macro use "
+        "correct compiler macro for getting the whole function name. "
+        "Define BOOST_PFR_CORE_NAME_USER_DEFINED_PARSING to correct value after that."
+    );
+}
+
+consteval std::string_view name_of_field_parse(std::string_view sv) noexcept {
+#if defined(BOOST_PFR_CORE_NAME_USER_DEFINED_PARSING)
+    constexpr auto s = detail::make_core_name_skip BOOST_PFR_CORE_NAME_USER_DEFINED_PARSING;
+#elif defined(_MSC_VER)
     // sizeof("auto __cdecl boost::pfr::detail::name_of_field_impl<") - 1, sizeof(">(void) noexcept") - 1
-    constexpr auto fn = detail::name_of_field_parse(sv, 52, 16, "->");
-#elif __clang__
-    constexpr auto sv = __PRETTY_FUNCTION__;
+    constexpr auto s = detail::make_core_name_skip(52, 16, "->");
+#elif defined(__clang__)
     // sizeof("auto boost::pfr::detail::name_of_field_impl() [MsvcWorkaround = ") - 1, sizeof("}]") - 1
-    constexpr auto fn = detail::name_of_field_parse(sv, 64, 2, ".");
-#else // GCC
-    constexpr auto sv = __PRETTY_FUNCTION__;
+    constexpr auto s = detail::make_core_name_skip(64, 2, ".");
+#elif defined(__GNUC__)
     // sizeof("consteval auto boost::pfr::detail::name_of_field_impl() [with MsvcWorkaround = ") - 1, sizeof(")]") - 1
-    constexpr auto fn = detail::name_of_field_parse(sv, 79, 2, "::");
+    constexpr auto s = detail::make_core_name_skip(79, 2, "::");
+#else
+    // Deafult code for other platforms... Just skip nothing!
+    constexpr auto s = detail::make_core_name_skip(0, 0, "");
+#endif
+    return detail::apply_core_name_skip(sv, s);
+}
+
+template <typename MsvcWorkaround, auto ptr>
+consteval auto name_of_field_impl() noexcept {
+
+#if defined(BOOST_PFR_FUNCTION_SIGNATURE)
+    constexpr auto fn = detail::name_of_field_parse(BOOST_PFR_FUNCTION_SIGNATURE);
+    detail::assert_compile_time_legths<!fn.empty()>();
+#elif defined(__FUNCSIG__)
+    constexpr auto fn = detail::name_of_field_parse(__FUNCSIG__);
+    detail::assert_compile_time_legths<!fn.empty()>();
+#elif defined(__PRETTY_FUNCTION__) \
+                || defined(__GNUC__) \
+                || defined(__clang__)
+    constexpr auto fn = detail::name_of_field_parse(__PRETTY_FUNCTION__);
+    detail::assert_compile_time_legths<!fn.empty()>();
+#else
+    constexpr std::string_view fn = "";
+    detail::failed_to_get_function_name<MsvcWorkaround>();
 #endif
+
     auto res = std::array<char, fn.size()+1>{};
     std::ranges::copy(fn, res.begin());
     return res;

test/core_name/Jamfile.v2

@@ -60,6 +60,7 @@ test-suite pfr_tests
     [ run fields_names_constexpr.cpp : : : : ]
     [ run fields_names_nonascii.cpp : : : <toolset>msvc:<cxxflags>"/utf-8" : ]
     [ run fields_names_big.cpp : : : <toolset>msvc:<cxxflags>"/bigobj" : ]
+    [ run print_name.cpp : : : <test-info>always_show_run_output ]
   ;
 
 

test/core_name/print_name.cpp

@@ -0,0 +1,33 @@
+// 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
+//
+
+#include <iostream>
+
+// This cpp file:
+// * tests BOOST_PFR_CORE_NAME_USER_DEFINED_PARSING macro
+// * outputs full name of the function so that PFRs extraction of field name could be adjust to new compiler without requesting regression tester's help
+#define BOOST_PFR_CORE_NAME_USER_DEFINED_PARSING (0,0,false,"")
+#include <boost/pfr/core_name.hpp>
+
+namespace user_defined_namespace {
+    struct user_defined_class { int user_defined_field; };
+}
+
+int main()
+{
+    using namespace boost::pfr;
+
+    std::cout << "user_defined_namespace::user_defined_class::user_defined_field: "
+        << get_name<0, user_defined_namespace::user_defined_class>() << '\n';
+
+
+    return 0;
+}
+