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From: "webrown.cpp at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/100687] New: [modules, concepts] imported concept gives different result Date: Wed, 19 May 2021 22:56:45 +0000 [thread overview] Message-ID: <bug-100687-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100687 Bug ID: 100687 Summary: [modules, concepts] imported concept gives different result Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: webrown.cpp at gmail dot com Target Milestone: --- Using recent trunk [g++-HEAD (Homebrew GCC HEAD-5380e3c) 12.0.0 20210513], compiling with significant flags -std=c++23 -fmodules-ts -c. I have two source files, as follows: ////////////////////// export module bug_a; template< class T > inline constexpr bool probe = false; // template< class R, class C > inline constexpr bool probe<R C::* > = true; export template< class T > concept mbr_ptr = probe<T>; struct S { int f( ); }; using mf_t = decltype( &S::f ); static_assert( mbr_ptr< mf_t > ); ////////////////////// This bug_a module compiles successfully. In particular, the static_assert passes. ////////////////////// export module bug_b; import bug_a; struct S { int f( ); }; using mf_t = decltype( &S::f ); static_assert( mbr_ptr< mf_t > ); ////////////////////// This bug_b module does not compile. The diagnostics are reproduced below, including the somewhat mysterious lone apostrophe: bug_b.cc:8:16: error: static assertion failed 8 | static_assert( mbr_ptr< mf_t > ); | ^~~~~~~~~~~~~~~ bug_b.cc:8:16: note: constraints not satisfied ' bug_a.cc:12: confused by earlier errors, bailing out Please note that the static_assert and supporting declarations in module bug_a are identical to those in module bug_a, yet one compiles while the other does not. Thus we seem to have two problems: (1) the lone apostrophe amongst the diagnostics, and (2) the inconsistent evaluation of identical expressions. Finally, please note that if I use a class template (instead of the variable template) in module bug_a, both modules' static_asserts now compile without complaint: ////////////////////// template< class T > struct probe { static constexpr bool value = false; }; // template< class R, class C > struct probe<R C::*> { static constexpr bool value = true; }; export template< class T > concept mbr_ptr = probe<T>::value; //////////////////////
next reply other threads:[~2021-05-19 22:56 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-19 22:56 webrown.cpp at gmail dot com [this message] 2021-11-25 0:37 ` [Bug c++/100687] " johelegp at gmail dot com 2022-03-23 22:23 ` johelegp at gmail dot com 2022-09-22 12:57 ` ppalka at gcc dot gnu.org
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