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do not store values with EBO since it can lead to name lookup ambiguity #1954

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Merged
ericniebler merged 1 commit into from
Mar 23, 2026
+11 −25
Merged

do not store values with EBO since it can lead to name lookup ambiguity #1954

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36 changes: 11 additions & 25 deletions include/stdexec/__detail/__any.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -455,31 +455,10 @@ namespace STDEXEC::__any
}

private:
STDEXEC_ATTRIBUTE(no_unique_address)
_Value __val_;
};

// A specialization of __box to take advantage of EBO (empty base optimization):
template <class _Value>
requires std::is_empty_v<_Value> && (!std::is_final_v<_Value>)
struct STDEXEC_ATTRIBUTE(empty_bases) __box<_Value> : private _Value
{
constexpr explicit __box(_Value __value) noexcept
: _Value(std::move(__value))
{}

template <class... _Args>
constexpr explicit __box(_Args &&...__args) noexcept
: _Value(static_cast<_Args &&>(__args)...)
{}

template <class _Self>
[[nodiscard]]
static constexpr auto __value_(_Self &&__self) noexcept -> auto &&
{
return std::forward<__copy_cvref_t<_Self, _Value>>(__self);
}
};

template <class _Interface, __box_kind _BoxKind>
concept __has_box_kind = std::remove_reference_t<_Interface>::__box_kind == _BoxKind;

Expand Down Expand Up @@ -1790,6 +1769,7 @@ namespace STDEXEC::__any
}

private:
using __model_type = __reference_proxy_model<_Interface>;
static_assert(sizeof(__iabstract<_Interface>) == sizeof(void *)); // sanity check

template <template <class> class>
Expand Down Expand Up @@ -1822,7 +1802,6 @@ namespace STDEXEC::__any
constexpr void __proxy_assign(_CvReferenceProxy *__proxy_ptr) noexcept
{
static_assert(_CvReferenceProxy::__box_kind == __box_kind::__proxy);
using __model_type = __reference_proxy_model<_Interface>;
constexpr bool __is_const_ = std::is_const_v<_CvReferenceProxy>;

if (__proxy_ptr == nullptr || __empty(*__proxy_ptr))
Expand All @@ -1849,14 +1828,17 @@ namespace STDEXEC::__any

// the proxy model is mutable so that a const __any_ptr can return non-const
// references from operator-> and operator*.
mutable __reference_proxy_model<_Interface> __reference_;
mutable __model_type __reference_;
};

//////////////////////////////////////////////////////////////////////////////////////////
// __any_ptr
template <template <class> class _Interface>
struct __any_ptr : __any_ptr_base<_Interface>
{
using __reference = __any_ptr_base<_Interface>::__model_type;
using __pointer = __reference *;

using __any_ptr_base<_Interface>::__any_ptr_base;
using __any_ptr_base<_Interface>::operator=;

Expand Down Expand Up @@ -1916,13 +1898,16 @@ namespace STDEXEC::__any
};

template <template <class> class _Interface, class _Base>
__any_ptr(_Interface<_Base> *) -> __any_ptr<_Interface>;
STDEXEC_HOST_DEVICE_DEDUCTION_GUIDE __any_ptr(_Interface<_Base> *) -> __any_ptr<_Interface>;

//////////////////////////////////////////////////////////////////////////////////////////
// __any_const_ptr
template <template <class> class _Interface>
struct __any_const_ptr : __any_ptr_base<_Interface>
{
using __reference = __any_ptr_base<_Interface>::__model_type const;
using __pointer = __reference *;

using __any_ptr_base<_Interface>::__any_ptr_base;
using __any_ptr_base<_Interface>::operator=;

Expand Down Expand Up @@ -1975,6 +1960,7 @@ namespace STDEXEC::__any
};

template <template <class> class _Interface, class _Base>
STDEXEC_HOST_DEVICE_DEDUCTION_GUIDE
__any_const_ptr(_Interface<_Base> const *) -> __any_const_ptr<_Interface>;

//////////////////////////////////////////////////////////////////////////////////////////
Expand Down
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