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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/99957] New: Ill-formed std::pair construction supported Date: Wed, 07 Apr 2021 12:44:52 +0000 [thread overview] Message-ID: <bug-99957-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99957 Bug ID: 99957 Summary: Ill-formed std::pair construction supported Product: gcc Version: 11.0 Status: UNCONFIRMED Keywords: accepts-invalid Severity: minor Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: redi at gcc dot gnu.org Target Milestone: --- This shouldn't compile: #include <utility> struct move_only { move_only() = default; move_only(move_only&&) = default; }; move_only mo() { return {}; } std::pair<void*, move_only> p0(0, mo()); std::pair<void*, move_only> p1({}, mo()); According to the standard, these constructors are considered: pair(const first_type&, const second_type&); template<class U1, class U2> pair(U1&&, U2&&); For both p0 and p1, the first does not participate in overload resolution because second_type is not copy constructible. For p0, the second constructor does not participate because U1 is deduced as int, and a pointer cannot be constructed from int. For p1, U1 cannot be deduced from {}. The code compiles with libstdc++ because we have additional non-standard constructors, added by PR 40925 and described in https://gcc.gnu.org/pipermail/libstdc++/2021-April/052299.html (where I proposed to deprecate these non-standard constructors, and eventually remove them).
next reply other threads:[~2021-04-07 12:44 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-07 12:44 redi at gcc dot gnu.org [this message] 2021-04-07 12:56 ` [Bug libstdc++/99957] " redi at gcc dot gnu.org 2021-04-28 16:57 ` cvs-commit at gcc dot gnu.org 2021-04-28 16:57 ` cvs-commit at gcc dot gnu.org 2021-04-28 17:01 ` redi at gcc dot gnu.org
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