mirror of git://gcc.gnu.org/git/gcc.git
956a62aaa2
This change simplifies visitation for variants, by using INVOKE<R> for the visit<R> form, and explicitly specifying the tag types for raw visitation, instead of inferring them from the return types of the lambda functions used as visitors. * include/std/variant (__visit_with_index): Remove typedef. (__deduce_visit_result): New tag type. (__raw_visit, __raw_idx_visit): New helper functions for "raw" visitation of possibly-valueless variants, forwarding to __do_visit with the relevant tag type. (_Variant_storage<false, _Types...>::_M_reset_impl): Use __raw_visit and make lambda return void. (__variant_construct): Likewise. (_Copy_assign_base::operator=, _Move_assign_base::operator=): Use __raw_idx_visit and make lambda return void. (_Multi_array::__untag_result): Add metafunction to check the function pointer type for a tag type that dictates the kind of visitation. (_Multi_array<_Ret(*)(_Visitor, _Variants...), __first, __rest...>): Use decltype(auto) instead of tagged function pointer type. (__gen_vtable_impl): Remove bool non-type parameter and unused _Variant_tuple parameter. (__gen_vtable_impl::__visit_invoke_impl): Remove. (__gen_vtable_impl::__do_visit_invoke): Remove. (__gen_vtable_impl::__do_visit_invoke_r): Remove. (__gen_vtable_impl::__visit_invoke): Use if-constexpr and __invoke_r for the visit<R> case, rather than dispatching to separate functions. (_VARIANT_RELATION_FUNCTION_TEMPLATE): Use __raw_idx_visit and make lambda return void. (variant::swap): Likewise. (__do_visit): Replace two non-type template parameters with a single type parameter, so that the caller must specify the visitor's return type (or one of the tag types). (visit): Deduce a return type from the visitor and use the __deduce_visit_result tag to enforce that all overloads return the same type. (visit<R>): Call __do_visit<R> with explicit result type. (__variant_hash_call_base_impl::operator()): Use __raw_visit and make lambda return void. From-SVN: r271182 |
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README
file: libstdc++-v3/README New users may wish to point their web browsers to the file index.html in the 'doc/html' subdirectory. It contains brief building instructions and notes on how to configure the library in interesting ways.