This is the mail archive of the libstdc++@gcc.gnu.org mailing list for the libstdc++ project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [C++ PATCH, RFC] Implement new C++ intrinsics __is_assignable and __is_constructible.


2017-05-12 12:39 GMT+02:00 Ville Voutilainen <ville.voutilainen@gmail.com>:
> I have tested this with the full suite on Linux-PPC64. It works otherwise fine,
> but there's one snag: 20_util/unique_ptr/specialized_algorithms/swap_cxx17.cc
> fails, and it looks like the trait ends up instantiating the definition
> of a destructor, which then ends up being hard-error ill-formed.

I'm pretty sure that the library-based implementation does not
instantiate the destructor definition.

Your description sounds remotely similar to me to the current problem
of __is_trivially_constructible intrinsic, which seems to instantiate
the copy constructor definition albeit it (IMO) shouldn't:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80654

Could there be a similar cause?

- Daniel

> That is, we have
>
> struct C { };
> void swap(C&, C&) = delete;
> static_assert( !std::is_swappable_v<std::unique_ptr<int, C>> );
>
> struct D { D(D&&) = delete; };
> static_assert( !std::is_swappable_v<std::unique_ptr<int, D>> );
>
> The destructor definitions of unique_ptr<int, C> and unique_ptr<int D>
> are not valid because that destructor will try to call an operator()
> on those deleters, and they don't have that operator.
>
> The existing library implementation of is_constructible doesn't
> instantiate the destructor definitions, or if it does, they don't cause
> a hard error. This intrinsic trait approach behaves differently, and I would
> welcome any help fixing that problem.
>
> 2017-05-12  Ville Voutilainen  <ville.voutilainen@gmail.com>
>
>     c-family/
>
>     Implement new C++ intrinsics __is_assignable and __is_constructible.
>     * c-common.c (__is_assignable, __is_constructible): New.
>     * c-common.h (RID_IS_ASSIGNABLE, RID_IS_CONSTRUCTIBLE): Likewise.
>
>     cp/
>
>     Implement new C++ intrinsics __is_assignable and __is_constructible.
>     * cp-tree.h (CPTK_IS_ASSIGNABLE, CPTK_IS_CONSTRUCTIBLE): New.
>     (is_xible): New.
>     * cxx-pretty-print.c (pp_cxx_trait_expression): Handle
>     CPTK_IS_ASSIGNABLE and CPTK_IS_CONSTRUCTIBLE.
>     * method.c (is_xible_helper): New.
>     (is_trivially_xible): Adjust.
>     (is_xible): New.
>     * parser.c (cp_parser_primary_expression): Handle
>     RID_IS_ASSIGNABLE and RID_IS_CONSTRUCTIBLE.
>     (cp_parser_trait_expr): Likewise.
>     * semantics.c (trait_expr_value): Handle
>     CPTK_IS_ASSIGNABLE and CPTK_IS_CONSTRUCTIBLE.
>
>     libstdc++-v3/
>
>     Implement new C++ intrinsics __is_assignable and __is_constructible.
>     * include/std/type_traits (__do_is_static_castable_impl): Remove.
>     (__is_static_castable_impl, __is_static_castable_safe): Likewise.
>     (__is_static_castable, __do_is_direct_constructible_impl): Likewise.
>     (__is_direct_constructible_impl): Likewise.
>     (__is_direct_constructible_new_safe): Likewise.
>     (__is_base_to_derived_ref, __is_lvalue_to_rvalue_ref): Likewise.
>     (__is_direct_constructible_ref_cast): Likewise.
>     (__is_direct_constructible_new, __is_direct_constructible): Likewise.
>     (__do_is_nary_constructible_impl): Likewise.
>     (__is_nary_constructible_impl, __is_nary_constructible): Likewise.
>     (__is_constructible_impl): Likewise.
>     (is_constructible): Call the intrinsic.
>     (__is_assignable_helper): Remove.
>     (is_assignable): Call the intrinsic.
>     (is_trivially_constructible): Likewise.
>     (is_trivially_assignable): Likewise.
>     (testsuite/20_util/declval/requirements/1_neg.cc): Adjust.
>     (testsuite/20_util/make_signed/requirements/typedefs_neg.cc): Likewise.
>     (testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc):
>     Likewise.



-- 

________________________________
SavedURI :Show URLShow URLSavedURI :
SavedURI :Hide URLHide URLSavedURI :
https://mail.google.com/_/scs/mail-static/_/js/k=gmail.main.de.LEt2fN4ilLE.O/m=m_i,t,it/am=OCMOBiHj9kJxhnelj6j997_NLil29vVAOBGeBBRgJwD-m_0_8B_AD-qOEw/rt=h/d=1/rs=AItRSTODy9wv1JKZMABIG3Ak8ViC4kuOWA?random=1395770800154https://mail.google.com/_/scs/mail-static/_/js/k=gmail.main.de.LEt2fN4ilLE.O/m=m_i,t,it/am=OCMOBiHj9kJxhnelj6j997_NLil29vVAOBGeBBRgJwD-m_0_8B_AD-qOEw/rt=h/d=1/rs=AItRSTODy9wv1JKZMABIG3Ak8ViC4kuOWA?random=1395770800154
________________________________


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]