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From: "danakj at orodu dot net" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/107544] New: Friended struct with concept gives different output in clang/gcc/MSVC Date: Sun, 06 Nov 2022 21:45:15 +0000 [thread overview] Message-ID: <bug-107544-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107544 Bug ID: 107544 Summary: Friended struct with concept gives different output in clang/gcc/MSVC Product: gcc Version: 12.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: danakj at orodu dot net Target Milestone: --- I don't know which compiler is right, but all three give a different output. So I will report it here, as the GCC result looks wrong and exposes private data. https://godbolt.org/z/7Pq3eWhc8 ``` #include <compare> #include <concepts> #include <iostream> template <class T> concept HasTag = requires { T::Tag; requires std::same_as<decltype(T::Tag), const bool>; }; template <class T> struct check_tag final { static constexpr bool value() requires(!HasTag<T>) { return false; } static constexpr bool value() requires(HasTag<T>) { return T::Tag; }; }; struct S { private: template <class T> friend struct check_tag; static constexpr bool Tag = true; }; int main() { std::cout << HasTag<S> << "\n"; std::cout << check_tag<S>::value() << "\n"; } ``` Clang output (the concept sees private data if used in friend): 0 1 GCC output (the concept always sees private data): 1 1 MSVC output (the concept never sees private data): 0 0
next reply other threads:[~2022-11-06 21:45 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-11-06 21:45 danakj at orodu dot net [this message] 2022-11-06 21:47 ` [Bug c++/107544] " danakj at orodu dot net 2022-11-06 21:49 ` pinskia at gcc dot gnu.org 2022-11-06 21:49 ` pinskia at gcc dot gnu.org 2022-11-06 21:55 ` danakj at orodu dot net
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