Calling std::get will check some static assertions and also do a runtime
check for a valid index before calling __detail::__variant::__get. The
std::visit function already handles the case where any variant has an
invalid index, so __get can be used directly in __visit_invoke.
* include/std/variant (__gen_vtable_impl::__visit_invoke): Call __get
directly instead of get, as caller ensures correct index is used.
(holds_alternative, get, get_if): Remove redundant inline specifiers.
(_VARIANT_RELATION_FUNCTION_TEMPLATE): Likewise.
Tested x86_64-linux, committed to trunk.
commit 79a88f5377344677fae1a21028293e8943eea209
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Tue Oct 2 14:12:20 2018 +0100
Avoid redundant runtime checks in std::visit
Calling std::get will check some static assertions and also do a runtime
check for a valid index before calling __detail::__variant::__get. The
std::visit function already handles the case where any variant has an
invalid index, so __get can be used directly in __visit_invoke.
* include/std/variant (__gen_vtable_impl::__visit_invoke): Call
__get
directly instead of get, as caller ensures correct index is used.
(holds_alternative, get, get_if): Remove redundant inline
specifiers.
(_VARIANT_RELATION_FUNCTION_TEMPLATE): Likewise.
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 9289eef28cf..ff340cfc897 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -811,9 +811,8 @@ namespace __variant
{
using _Alternative = variant_alternative_t<__index, _Next>;
__element = __gen_vtable_impl<
- remove_reference_t<
- decltype(__element)>, tuple<_Variants...>,
- std::index_sequence<__indices..., __index>>::_S_apply();
+ remove_reference_t<decltype(__element)>, tuple<_Variants...>,
+ std::index_sequence<__indices..., __index>>::_S_apply();
}
};
@@ -826,11 +825,11 @@ namespace __variant
using _Array_type =
_Multi_array<_Result_type (*)(_Visitor&&, _Variants...)>;
- decltype(auto)
- static constexpr __visit_invoke(_Visitor&& __visitor, _Variants...
__vars)
+ static constexpr decltype(auto)
+ __visit_invoke(_Visitor&& __visitor, _Variants... __vars)
{
return std::__invoke(std::forward<_Visitor>(__visitor),
- std::get<__indices>(std::forward<_Variants>(__vars))...);
+ __variant::__get<__indices>(std::forward<_Variants>(__vars))...);
}
static constexpr auto
@@ -871,8 +870,8 @@ namespace __variant
} // namespace __detail
template<typename _Tp, typename... _Types>
- inline constexpr bool holds_alternative(const variant<_Types...>& __v)
- noexcept
+ constexpr bool
+ holds_alternative(const variant<_Types...>& __v) noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
@@ -880,7 +879,7 @@ namespace __variant
}
template<typename _Tp, typename... _Types>
- constexpr inline _Tp& get(variant<_Types...>& __v)
+ constexpr _Tp& get(variant<_Types...>& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
@@ -889,7 +888,7 @@ namespace __variant
}
template<typename _Tp, typename... _Types>
- constexpr inline _Tp&& get(variant<_Types...>&& __v)
+ constexpr _Tp&& get(variant<_Types...>&& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
@@ -899,7 +898,7 @@ namespace __variant
}
template<typename _Tp, typename... _Types>
- constexpr inline const _Tp& get(const variant<_Types...>& __v)
+ constexpr const _Tp& get(const variant<_Types...>& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
@@ -908,7 +907,7 @@ namespace __variant
}
template<typename _Tp, typename... _Types>
- constexpr inline const _Tp&& get(const variant<_Types...>&& __v)
+ constexpr const _Tp&& get(const variant<_Types...>&& __v)
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
"T should occur for exactly once in alternatives");
@@ -918,8 +917,7 @@ namespace __variant
}
template<size_t _Np, typename... _Types>
- constexpr inline
- add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
+ constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
get_if(variant<_Types...>* __ptr) noexcept
{
using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
@@ -932,7 +930,7 @@ namespace __variant
}
template<size_t _Np, typename... _Types>
- constexpr inline
+ constexpr
add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
get_if(const variant<_Types...>* __ptr) noexcept
{
@@ -946,7 +944,7 @@ namespace __variant
}
template<typename _Tp, typename... _Types>
- constexpr inline add_pointer_t<_Tp>
+ constexpr add_pointer_t<_Tp>
get_if(variant<_Types...>* __ptr) noexcept
{
static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
@@ -957,7 +955,7 @@ namespace __variant
}
template<typename _Tp, typename... _Types>
- constexpr inline add_pointer_t<const _Tp>
+ constexpr add_pointer_t<const _Tp>
get_if(const variant<_Types...>* __ptr)
noexcept
{
@@ -1277,7 +1275,7 @@ namespace __variant
{ &__detail::__variant::__erased_##__NAME< \
const variant&, __indices>... }; \
template<size_t... __indices> \
- constexpr inline bool \
+ constexpr bool \
_M_##__NAME(const variant& __rhs, \
std::index_sequence<__indices...>) const \
{ \
