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From: "richard-gccbugzilla at metafoo dot co.uk" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/60497] New: unique_ptr<T> tries to complete its type T even though it's not required to be a complete type Date: Tue, 11 Mar 2014 03:46:00 -0000 [thread overview] Message-ID: <bug-60497-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60497 Bug ID: 60497 Summary: unique_ptr<T> tries to complete its type T even though it's not required to be a complete type Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: richard-gccbugzilla at metafoo dot co.uk Consider: struct A; template<typename T> struct B { T t; }; struct Deleter { void operator()(B<A>*) const; }; std::unique_ptr<B<A>, Deleter> u; It's not *entirely* clear to me that this is valid, but I think it is intended to be. unique_ptr is required to support incomplete types like B<A>, but it's not obvious that it can't *try* to complete the type. (If it does, this won't compile, because B<A> has a field of incomplete type 'A'.) g++ 4.8 rejects this: <stdin>: In instantiation of 'struct B<A>': tuple:758:35: required from 'constexpr typename std::__add_ref<typename std::tuple_element<__i, std::tuple<_Elements ...> >::type>::type std::get(std::tuple<_Elements ...>&) [with long unsigned int __i = 0ul; _Elements = {B<A>*, Deleter}; typename std::__add_ref<typename std::tuple_element<__i, std::tuple<_Elements ...> >::type>::type = B<A>*&]' bits/unique_ptr.h:182:32: required from 'std::unique_ptr<_Tp, _Dp>::~unique_ptr() [with _Tp = B<A>; _Dp = Deleter]' <stdin>:5:34: required from here <stdin>:3:37: error: 'B<T>::t' has incomplete type <stdin>:2:10: error: forward declaration of 'struct A' This is ultimately a bug in std::tuple::get: template<std::size_t __i, typename... _Elements> constexpr typename __add_ref< typename tuple_element<__i, tuple<_Elements...>>::type >::type get(tuple<_Elements...>& __t) noexcept { return __get_helper<__i>(__t); } Note that this performs ADL to find __get_helper, which requires the associated classes of __t to be complete, and those include B<A>. So this reduces to: struct A; template<typename T> struct B { T t; }; std::tuple<B<A>*> t(nullptr); auto *p = std::get<0>(t); ... which is rejected in the same way.
next reply other threads:[~2014-03-11 3:46 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-03-11 3:46 richard-gccbugzilla at metafoo dot co.uk [this message] 2014-04-14 15:33 ` [Bug libstdc++/60497] " redi at gcc dot gnu.org 2014-04-15 19:16 ` redi at gcc dot gnu.org 2014-04-27 16:37 ` redi at gcc dot gnu.org 2014-04-27 16:38 ` redi at gcc dot gnu.org 2014-05-13 11:18 ` redi at gcc dot gnu.org 2014-05-13 14:30 ` redi at gcc dot gnu.org 2014-05-13 16:50 ` redi at gcc dot gnu.org 2014-05-13 17:22 ` redi at gcc dot gnu.org 2015-06-22 14:26 ` rguenth at gcc dot gnu.org 2021-04-30 13:55 ` redi at gcc dot gnu.org 2021-04-30 14:48 ` cvs-commit at gcc dot gnu.org
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