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From: "Darrell.Wright at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/97134] New: partial specialization not more specialized when using CNTTP Date: Mon, 21 Sep 2020 05:52:40 +0000 [thread overview] Message-ID: <bug-97134-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97134 Bug ID: 97134 Summary: partial specialization not more specialized when using CNTTP Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: Darrell.Wright at gmail dot com Target Milestone: --- g++, tried trunk on CE along with 10.2 and 10.1 will say the following code is not more specialized when JSONNAMETYPE is a CNTTP(json_name). When it's a NTTP(char const *) it is ok with it. The code works in MSVC's C++20 mode. https://godbolt.org/z/7v4nx5 #include <cstddef> #include <iostream> #include <string_view> #include <utility> template <std::size_t N> struct json_name { static_assert(N > 0); char const m_data[N]{}; private: template <std::size_t... Is> constexpr json_name(char const (&ptr)[N], std::index_sequence<Is...>) : m_data{ptr[Is]...} {} public: constexpr json_name(char const (&ptr)[N]) : json_name(ptr, std::make_index_sequence<N>{}) {} // Needed for copy_to_iterator [[nodiscard]] constexpr char const *begin() const { return m_data; } // Needed for copy_to_iterator [[nodiscard]] constexpr char const *end() const { return m_data + static_cast<ptrdiff_t>(size()); } [[nodiscard]] static constexpr std::size_t size() noexcept { return N - 1; } template <std::size_t M> constexpr bool operator==(json_name<M> const &rhs) const { if (N != M) { return false; } for (std::size_t n = 0; n < N; ++n) { if (m_data[n] != rhs.m_data[n]) { return false; } } return true; } constexpr operator std::string_view() const { return std::string_view(m_data, size()); } }; template <typename... Chars> json_name(Chars...) -> json_name<sizeof...(Chars)>; template <std::size_t N> json_name(char const (&)[N]) -> json_name<N>; #ifdef USE_CNTTP #define JSONNAMETYPE json_name #else #define JSONNAMETYPE char const * #endif template <JSONNAMETYPE Name, typename U> struct X : std::false_type { static constexpr std::string_view name = Name; }; template <JSONNAMETYPE Name> struct X<Name, bool> : std::true_type { static constexpr std::string_view name = Name; }; int main() { static constexpr char const A[] = "A"; static constexpr char const B[] = "B"; auto a = X<A, int>::name; auto b = X<B, bool>::name; std::cout << a << b << '\n'; }
next reply other threads:[~2020-09-21 5:52 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-09-21 5:52 Darrell.Wright at gmail dot com [this message] 2020-09-23 13:01 ` [Bug c++/97134] " ppalka at gcc dot gnu.org 2021-03-20 14:57 ` omer.rosler at gmail dot com 2021-04-09 21:20 ` ppalka at gcc dot gnu.org 2021-04-13 3:23 ` cvs-commit at gcc dot gnu.org 2021-04-13 3:23 ` ppalka at gcc dot gnu.org
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