Parser might be explicitly tagged as backward

include/boost/pfr/config.hpp

@@ -122,13 +122,13 @@
 #ifndef BOOST_PFR_CORE_NAME_PARSING
 #   if defined(_MSC_VER)
 // sizeof("auto __cdecl boost::pfr::detail::name_of_field_impl<") - 1, sizeof(">(void) noexcept") - 1
-#       define BOOST_PFR_CORE_NAME_PARSING (52, 16, "->")
+#       define BOOST_PFR_CORE_NAME_PARSING (52, 16, backward("->"))
 #   elif defined(__clang__)
 // sizeof("auto boost::pfr::detail::name_of_field_impl() [MsvcWorkaround = ") - 1, sizeof("}]") - 1
-#       define BOOST_PFR_CORE_NAME_PARSING (64, 2, ".")
+#       define BOOST_PFR_CORE_NAME_PARSING (64, 2, backward("."))
 #   elif defined(__GNUC__)
 // sizeof("consteval auto boost::pfr::detail::name_of_field_impl() [with MsvcWorkaround = ") - 1, sizeof(")]") - 1
-#       define BOOST_PFR_CORE_NAME_PARSING (79, 2, "::")
+#       define BOOST_PFR_CORE_NAME_PARSING (79, 2, backward("::"))
 #   else
 // Deafult parser for other platforms... Just skip nothing!
 #       define BOOST_PFR_CORE_NAME_PARSING (0, 0, "")

include/boost/pfr/detail/core_name20_static.hpp

@@ -29,31 +29,64 @@ 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;
+    bool is_backward;
+    std::string_view until_runtime;
+
+    consteval std::string_view fail() const noexcept {
+        return "";
+    }
+
+    consteval std::string_view apply(std::string_view sv) const noexcept {
+        sv.remove_prefix((std::min)(size_at_begin, sv.size()));
+        sv.remove_suffix((std::min)(size_at_end, sv.size()));
+        if (!more_at_runtime) {
+            if (!until_runtime.empty())
+                return fail(); ///< useless skip condition
+            return sv;
+        }
+        else {
+            // so, we're asked to skip more
+            if (until_runtime.empty())
+                return fail(); ///< condition to skip more wasn't specified
+            const auto found = is_backward ? sv.rfind(until_runtime)
+                                             : sv.find(until_runtime);
+                                             ;
+            const auto cut_until = found + until_runtime.size();
+            const auto safe_cut_until = (std::min)(cut_until, sv.size());
+            return sv.substr(safe_cut_until);
+        }
+    }
+};
+
+struct backward {
+    explicit consteval backward(std::string_view value) noexcept
+        : value(value)
+    {}
+    
+    std::string_view value;
 };
 
 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
+                                             std::string_view until_runtime) noexcept
 {
-    return core_name_skip{size_at_begin, size_at_end, more_at_runtime, until_runtime_last};
+    return core_name_skip{size_at_begin, size_at_end, more_at_runtime, false, until_runtime};
 }
 
 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
+                                             bool more_at_runtime,
+                                             backward until_runtime) noexcept
 {
-    return core_name_skip{size_at_begin, size_at_end, true, until_runtime_last};
+    return core_name_skip{size_at_begin, size_at_end, more_at_runtime, true, until_runtime.value};
 }
 
-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;
-                             ;
+consteval core_name_skip make_core_name_skip(std::size_t size_at_begin,
+                                             std::size_t size_at_end,
+                                             auto until_runtime) noexcept
+{
+    return detail::make_core_name_skip(size_at_begin, size_at_end, true, until_runtime);
 }
 
 template <bool Condition>
@@ -85,7 +118,14 @@ consteval auto name_of_field_impl() noexcept {
         return detail::make_stdarray<char>(0);
     } else {
         constexpr auto skip = detail::make_core_name_skip BOOST_PFR_CORE_NAME_PARSING;
-        constexpr auto fn = detail::apply_core_name_skip(sv, skip);
+        static_assert(
+            skip.more_at_runtime || skip.until_runtime.empty(),
+            "====================> Boost.PFR: Parser configured in a wrong way. "
+            "It wasn't requested to skip more, but such skip condition was specified in vain. "
+            "Please read your definition of BOOST_PFR_CORE_NAME_PARSING macro patiently "
+            "and fix it."
+        );
+        constexpr auto fn = skip.apply(sv);
         auto res = std::array<char, fn.size()+1>{};
         detail::assert_compile_time_legths<!fn.empty()>();
         std::ranges::copy(fn, res.begin());

test/core_name/Jamfile.v2

@@ -62,6 +62,8 @@ test-suite pfr_name_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 fields_names_correctly_configured_compiler.cpp : : : : ]
+    [ run fields_names_internal_parser.cpp : : : : ]
     [ run print_name.cpp : : : <test-info>always_show_run_output ]
   ;
 

test/core_name/compile-fail/fields_names_wrongly_configured_compiler.cpp

@@ -0,0 +1,21 @@
+// 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
+//
+
+#define BOOST_PFR_FUNCTION_SIGNATURE "dummy"
+#define BOOST_PFR_CORE_NAME_PARSING (3,2,false,"")
+#include <boost/pfr/core_name.hpp>
+
+struct A { int field; };
+
+int main() {
+    (void)boost::pfr::get_name<0, A>(); // Must be a compile time error
+}
+
+

test/core_name/fields_names_correctly_configured_compiler.cpp

@@ -0,0 +1,25 @@
+// 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
+//
+
+#define BOOST_PFR_FUNCTION_SIGNATURE " *[field] "
+#define BOOST_PFR_CORE_NAME_PARSING (3,2,false,"")
+#include <boost/pfr/core_name.hpp>
+
+#include <boost/core/lightweight_test.hpp>
+
+struct A { int field; };
+
+int main() {
+    BOOST_TEST_EQ( ((boost::pfr::get_name<0,A>())), "field");
+
+    return boost::report_errors();
+}
+
+

test/core_name/fields_names_internal_parser.cpp

@@ -0,0 +1,58 @@
+// 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 <boost/pfr/core_name.hpp>
+#include <string_view>
+
+#include <boost/core/lightweight_test.hpp>
+
+namespace testing
+{
+
+constexpr std::string_view fake_func_name = " ******************** [fake_text1->fake_text2->fake_text3] **********";    
+
+void test_general()
+{
+    namespace detail = boost::pfr::detail;
+    using detail::backward;
+    BOOST_TEST_EQ(detail::make_core_name_skip(23, 12, false, "").apply(fake_func_name), "fake_text1->fake_text2->fake_text3");
+    BOOST_TEST_EQ(detail::make_core_name_skip(23, 12, backward("->")).apply(fake_func_name), "fake_text3");
+    BOOST_TEST_EQ(detail::make_core_name_skip(23, 12, "->").apply(fake_func_name), "fake_text2->fake_text3");
+    BOOST_TEST_EQ(detail::make_core_name_skip(23, 12, true, backward("->")).apply(fake_func_name), "fake_text3");
+    BOOST_TEST_EQ(detail::make_core_name_skip(23, 12, true, "->").apply(fake_func_name), "fake_text2->fake_text3");
+}
+
+void test_undefided_parser()
+{
+    namespace detail = boost::pfr::detail;
+    using detail::backward;
+    BOOST_TEST_EQ(detail::make_core_name_skip(0, 0, backward("")).apply(fake_func_name), "");
+    BOOST_TEST_EQ(detail::make_core_name_skip(0, 0, "").apply(fake_func_name), "");
+    BOOST_TEST_EQ(detail::make_core_name_skip(0, 0, true, backward("")).apply(fake_func_name), "");
+    BOOST_TEST_EQ(detail::make_core_name_skip(0, 0, true, "").apply(fake_func_name), "");
+}
+
+void test_identity_parser()
+{
+    namespace detail = boost::pfr::detail;
+    using detail::backward;
+    BOOST_TEST_EQ(detail::make_core_name_skip(0, 0, false, backward("")).apply(fake_func_name), fake_func_name);
+    BOOST_TEST_EQ(detail::make_core_name_skip(0, 0, false, "").apply(fake_func_name), fake_func_name);
+}
+}
+
+int main() {
+    testing::test_general();
+    testing::test_undefided_parser();
+    testing::test_identity_parser();
+
+    return boost::report_errors();
+}
+