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* [Bug c++/107544] New: Friended struct with concept gives different output in clang/gcc/MSVC @ 2022-11-06 21:45 danakj at orodu dot net 2022-11-06 21:47 ` [Bug c++/107544] " danakj at orodu dot net ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: danakj at orodu dot net @ 2022-11-06 21:45 UTC (permalink / raw) To: gcc-bugs 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107544] Friended struct with concept gives different output in clang/gcc/MSVC 2022-11-06 21:45 [Bug c++/107544] New: Friended struct with concept gives different output in clang/gcc/MSVC danakj at orodu dot net @ 2022-11-06 21:47 ` danakj at orodu dot net 2022-11-06 21:49 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: danakj at orodu dot net @ 2022-11-06 21:47 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107544 --- Comment #1 from danakj at orodu dot net --- Clang report: https://github.com/llvm/llvm-project/issues/58833 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107544] Friended struct with concept gives different output in clang/gcc/MSVC 2022-11-06 21:45 [Bug c++/107544] New: Friended struct with concept gives different output in clang/gcc/MSVC danakj at orodu dot net 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 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2022-11-06 21:49 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107544 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=104111 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- I think this is a dup of bug 104111. Specifically there is an issue reported against the C++ standard too: https://cplusplus.github.io/CWG/issues/2589.html --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- I think this is a dup of bug 104111. Specifically there is an issue reported against the C++ standard too: https://cplusplus.github.io/CWG/issues/2589.html ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107544] Friended struct with concept gives different output in clang/gcc/MSVC 2022-11-06 21:45 [Bug c++/107544] New: Friended struct with concept gives different output in clang/gcc/MSVC danakj at orodu dot net 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 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2022-11-06 21:49 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107544 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=104111 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- I think this is a dup of bug 104111. Specifically there is an issue reported against the C++ standard too: https://cplusplus.github.io/CWG/issues/2589.html --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- I think this is a dup of bug 104111. Specifically there is an issue reported against the C++ standard too: https://cplusplus.github.io/CWG/issues/2589.html ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107544] Friended struct with concept gives different output in clang/gcc/MSVC 2022-11-06 21:45 [Bug c++/107544] New: Friended struct with concept gives different output in clang/gcc/MSVC danakj at orodu dot net ` (2 preceding siblings ...) 2022-11-06 21:49 ` pinskia at gcc dot gnu.org @ 2022-11-06 21:55 ` danakj at orodu dot net 3 siblings, 0 replies; 5+ messages in thread From: danakj at orodu dot net @ 2022-11-06 21:55 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107544 --- Comment #4 from danakj at orodu dot net --- It looks related but I am not sure it is a duplicate. In this case, the concept is being used from a non-friend context first and still accessing the private data. In that bug, they demonstrate clang having the same output, but here clang and GCC differ as well. ``` std::cout << HasTag<S> << "\n"; std::cout << check_tag<S>::value() << "\n"; ``` Reordering these statements does not change the output. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-11-06 21:55 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-11-06 21:45 [Bug c++/107544] New: Friended struct with concept gives different output in clang/gcc/MSVC danakj at orodu dot net 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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