On Thu, 24 Jun 2021 at 22:11, Tim Song wrote: > > That example violates http://eel.is/c++draft/unique.ptr.runtime.general#3
Even though it's undefined I committed a workaround to allow it, because it breaks LLVM: https://gcc.gnu.org/pipermail/libstdc++/2021-June/052851.html (I forgot to send that mail as a reply to this thread, sorry). > On Thu, Jun 24, 2021 at 1:55 PM Patrick Palka via Gcc-patches > <gcc-patches@gcc.gnu.org> wrote: > > > > On Thu, 24 Jun 2021, Jonathan Wakely via Libstdc++ wrote: > > > > > The LWG issue proposes to add a conditional noexcept-specifier to > > > std::unique_ptr's dereference operator. The issue is currently in > > > Tentatively Ready status, but even if it isn't voted into the draft, we > > > can do it as a conforming extensions. This commit also adds a similar > > > noexcept-specifier to operator[] for the unique_ptr<T[], D> partial > > > specialization. > > > > The conditional noexcept added to unique_ptr<T[]>::operator[] seems to break > > the case where T is complete only after the fact: > > > > struct T; > > extern std::unique_ptr<T[]> p; > > auto& t = p[1]; > > struct T { }; > > > > /include/c++/12.0.0/bits/unique_ptr.h: In instantiation of ‘typename > > std::add_lvalue_reference<_Tp>::type std::unique_ptr<_Tp [], > > _Dp>::operator[](std::size_t) co > > nst [with _Tp = A; _Dp = std::default_delete<A []>; typename > > std::add_lvalue_reference<_Tp>::type = A&; std::size_t = long unsigned > > int]’: > > testcase.cc:5:14: required from here > > /include/c++/12.0.0/bits/unique_ptr.h:658:48: error: invalid use of > > incomplete type ‘struct A’ > > 658 | > > noexcept(noexcept(std::declval<pointer>()[std::declval<size_t&>()])) > > | ~~~~~~~~~~~~~~~~~~~~~~~^ > > testcase.cc:3:8: note: forward declaration of ‘struct A’ > > 3 | struct A; > > | ^ > > > > > > > > Also ensure that all dereference operators for shared_ptr are noexcept, > > > and adds tests for the std::optional accessors modified by the issue, > > > which were already noexcept in our implementation. > > > > > > Signed-off-by: Jonathan Wakely <jwak...@redhat.com> > > > > > > libstdc++-v3/ChangeLog: > > > > > > * include/bits/shared_ptr_base.h (__shared_ptr_access::operator[]): > > > Add noexcept. > > > * include/bits/unique_ptr.h (unique_ptr::operator*): Add > > > conditional noexcept as per LWG 2762. > > > * testsuite/20_util/shared_ptr/observers/array.cc: Check that > > > dereferencing cannot throw. > > > * testsuite/20_util/shared_ptr/observers/get.cc: Likewise. > > > * testsuite/20_util/optional/observers/lwg2762.cc: New test. > > > * testsuite/20_util/unique_ptr/lwg2762.cc: New test. > > > > > > Tested powerpc64le-linux. Committed to trunk. > > > > > > >
