[PATCH] libstdc++: Optimize functor storage for transform views iterators.
Hewill Kang
hewillk@gmail.com
Fri Nov 14 13:17:44 GMT 2025
I can't help but wonder, if this patch can't optimize for lambdas (users
generally don't explicitly spell `static`), then I don't see much point in
this optimization.
I think the case of `Obfuscate` is unlikely to occur. The view class will
move the original object to the `movable_box` via `std::move(fun)`, so
`this` pointer has already changed.
If we could actually create such a pretentious functor with a disgusting
operator(), I think the standard has every reason not to care about it.
Therefore, after thinking about it, I think we should perhaps follow
p3117r1 and use `is_empty_v<F> && is_trivially_default_constructible_v<F> &&
is_trivially_destructible_v<F>` to optimize lambda. Because that is
undoubtedly the most common use case (and the most worthy of
optimization). This is something this patch should be interested in.
Tomasz Kaminski <tkaminsk@redhat.com> 於 2025年11月14日 週五 下午5:36寫道：
>
>
> On Fri, Nov 14, 2025 at 10:24 AM Hewill Kang <hewillk@gmail.com> wrote:
>
>> Yes, I do not think anything in standard clearly states the that
>>> following is
>>> allowed to fail:
>>> struct Obfuscate
>>> {
>>> int operator()(int x) const
>>> { return x + static_assert<unintptr_t>(this); }
>>> };
>>
>>
>>> std::vector<int> v{1, 2, 3, 4, 5};
>>> auto tv = v | std::transform(Obfuscate{});
>>> VERIFY( ranges::equal(tv, tv) );
>>> But storing an empty object in an iterator will break.
>>
>>
>> This is a very good observation, so recreating empty objects is still
>> problematic.
>> It also seems to suggest that
>> https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p3117r1.html (most
>> likely a follow-up to this patch) and
>> https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p3705r1.html
>> might have issues with this.
>> For example, `operator()` uses `this` or `operator==` uses `this`.
>>
> Yes, static operator() is bulletproof way of ensuring that it does not
> depend on object identity,
> even if the object itself is not empty. We do not need to use
> heuristics based on size anymore.
>
>>
>> Tomasz Kaminski <tkaminsk@redhat.com> 於 2025年11月14日 週五 下午2:36寫道：
>>
>>>
>>>
>>> On Fri, Nov 14, 2025 at 4:16 AM Patrick Palka <ppalka@redhat.com> wrote:
>>>
>>>> On Thu, 13 Nov 2025, Tomasz Kamiński wrote:
>>>>
>>>> > The iterators for transform views (views::transform,
>>>> views::zip_transform,
>>>> > and views::adjacent_transform) now store a __detail::__func_handle
>>>> instead
>>>> > of a pointer to the view object (_M_parent).
>>>> >
>>>> > The behavior of the __func_handle specialization depends on the
>>>> _FunctorType
>>>> > template parameter:
>>>> > * _FunctionPtr: Used if the functor is a function pointer. The
>>>> pointer is
>>>> > stored directly in __func_handle and the iterator, avoiding double
>>>> > indirection through a pointer to the function pointer.
>>>> > * _MemberPointer: Used for data or function member pointers. This
>>>> behaves
>>>> > similarly to _FunctionPtr, but uses __invoke for invocations.
>>>> > * _StaticOperator: Used if the operator() selected by overload
>>>> resolution
>>>> > for the iterator reference is static. In this case, __func_handle
>>>> is empty,
>>>> > reducing the iterator size.
>>>> > * _Statefull: Used for all remaining cases. __func_handle stores a
>>>> pointer
>>>> > to the functor object stored within the view. Only for this
>>>> specialization is
>>>> > the cv-qualification of the functor template parameter (_Fn)
>>>> relevant, and
>>>> > both const and mutable specializations are generated.
>>>>
>>>> FWIW it's spelled 'stateful' with just one l.
>>>>
>>>> I guess you concluded that this optimization is unsafe for empty objects
>>>> with non-static operator()?
>>>>
>>> Yes, I do not think anything in standard clearly states the that
>>> following is
>>> allowed to fail:
>>> struct Obfuscate
>>> {
>>> int operator()(int x) const
>>> { return x + static_assert<unintptr_t>(this); }
>>> };
>>>
>>> std::vector<int> v{1, 2, 3, 4, 5};
>>> auto tv = v | std::transform(Obfuscate{});
>>> VERIFY( ranges::equal(tv, tv) );
>>>
>>> But storing an empty object in an iterator will break.
>>>
>>>
>>>> >
>>>> > As a consequence of these changes, the iterators of transform views
>>>> no longer
>>>> > depend on the view object when __func_handle is specialized for
>>>> values other
>>>> > than _Statefull. The corresponding views are not marked as
>>>> borrowed_range,
>>>> > as they are not marked as such in the standard.
>>>> >
>>>> > Storing function member pointers directly increases the iterator size
>>>> in that
>>>> > specific case, but this is deemed beneficial for consistent treatment
>>>> of
>>>> > function and data member pointers.
>>>> >
>>>> > To avoid materializing temporaries when the underlying iterator(s)
>>>> return a
>>>> > prvalue, the _M_call_deref and _M_call_subscript methods of
>>>> __func_handle are
>>>> > defined to accept the iterator(s), which are then dereferenced as
>>>> arguments
>>>> > of the functor.
>>>> >
>>>> > Using _Fd::operator()(*__iters...) inside requires expression is only
>>>> > supported since clang-20, however at the point of GCC-16 release,
>>>> clang-22
>>>> > should be already available.
>>>> >
>>>> > libstdc++-v3/ChangeLog:
>>>> >
>>>> > * include/std/ranges (__detail::__func_handle)
>>>> > (__detail::func_handle_t): Define.
>>>> > (transform_view::_Iterator, zip_transform_view::_Iterator)
>>>> > (adjacent_tranform_view::_Iterator): Replace pointer to view
>>>> > (_M_parent) with pointer to functor (_M_fun). Update
>>>> constructors
>>>> > to cosntruct _M_fun from *__parent->_M_fun. Define operator* and
>>>> > operator[] in terms of _M_call_deref and _M_call_subscript.
>>>> > * testsuite/std/ranges/adaptors/adjacent_transform/1.cc: New
>>>> tests.
>>>> > * testsuite/std/ranges/adaptors/transform.cc: New tests.
>>>> > * testsuite/std/ranges/zip_transform/1.cc: New tests.
>>>> > ---
>>>> > Tested transform view files locally. More testing in progress.
>>>> >
>>>> > libstdc++-v3/include/std/ranges | 214
>>>> +++++++++++++++---
>>>> > .../ranges/adaptors/adjacent_transform/1.cc | 97 ++++++++
>>>> > .../std/ranges/adaptors/transform.cc | 118 +++++++++-
>>>> > .../testsuite/std/ranges/zip_transform/1.cc | 101 +++++++++
>>>> > 4 files changed, 493 insertions(+), 37 deletions(-)
>>>> >
>>>> > diff --git a/libstdc++-v3/include/std/ranges
>>>> b/libstdc++-v3/include/std/ranges
>>>> > index ae57b9a0809..28b4f1d2b90 100644
>>>> > --- a/libstdc++-v3/include/std/ranges
>>>> > +++ b/libstdc++-v3/include/std/ranges
>>>> > @@ -286,6 +286,138 @@ namespace ranges
>>>> > operator->() const noexcept
>>>> > { return std::__addressof(_M_value); }
>>>> > };
>>>> > +
>>>> > + enum class _FunctorType
>>>> > + {
>>>> > + _FunctionPtr,
>>>> > + _MemberPtr,
>>>> > + _StaticOperator,
>>>> > + _Statefull,
>>>> > + };
>>>> > +
>>>> > + template<typename _Fn, _FunctorType __ft>
>>>> > + struct __func_handle
>>>> > + {
>>>> > + __func_handle() = default;
>>>> > +
>>>> > + constexpr explicit
>>>> > + __func_handle(_Fn& __func) noexcept
>>>> > + : _M_ptr(std::addressof(__func))
>>>> > + { }
>>>> > +
>>>> > + template<typename _Un>
>>>> > + requires (!is_const_v<_Un>) && is_same_v<const _Un, _Fn>
>>>> > + constexpr explicit
>>>> > + __func_handle(__func_handle<_Un, __ft> __other) noexcept
>>>> > + : _M_ptr(__other._M_ptr)
>>>> > + { }
>>>> > +
>>>> > + template<typename... _Iters>
>>>> > + constexpr decltype(auto)
>>>> > + _M_call_deref(const _Iters&... __iters) const
>>>> > + noexcept(noexcept((*_M_ptr)(*__iters...)))
>>>> > + { return (*_M_ptr)(*__iters...); }
>>>> > +
>>>> > + template<typename _DistType, typename... _Iters>
>>>> > + constexpr decltype(auto)
>>>> > + _M_call_subscript(const _DistType __n, const _Iters&...
>>>> __iters) const
>>>> > +
>>>> noexcept(noexcept((*_M_ptr)(__iters[iter_difference_t<_Iters>(__n)]...)))
>>>> > + { return
>>>> (*_M_ptr)(__iters[iter_difference_t<_Iters>(__n)]...); }
>>>> > +
>>>> > + private:
>>>> > + _Fn* _M_ptr = nullptr;
>>>> > +
>>>> > + template<typename, _FunctorType>
>>>> > + friend struct __func_handle;
>>>> > + };
>>>> > +
>>>> > + template<typename _Fn>
>>>> > + struct __func_handle<_Fn, _FunctorType::_FunctionPtr>
>>>> > + {
>>>> > + __func_handle() = default;
>>>> > +
>>>> > + constexpr explicit
>>>> > + __func_handle(_Fn __func) noexcept
>>>> > + : _M_ptr(__func)
>>>> > + { }
>>>> > +
>>>> > + template<typename... _Iters>
>>>> > + constexpr decltype(auto)
>>>> > + _M_call_deref(const _Iters&... __iters) const
>>>> > + noexcept(noexcept(_M_ptr(*__iters...)))
>>>> > + { return _M_ptr(*__iters...); }
>>>> > +
>>>> > + template<typename _DistType, typename... _Iters>
>>>> > + constexpr decltype(auto)
>>>> > + _M_call_subscript(const _DistType __n, const _Iters&...
>>>> __iters) const
>>>> > +
>>>> noexcept(noexcept(_M_ptr(__iters[iter_difference_t<_Iters>(__n)]...)))
>>>> > + { return _M_ptr(__iters[iter_difference_t<_Iters>(__n)]...); }
>>>> > +
>>>> > + private:
>>>> > + _Fn _M_ptr = nullptr;
>>>> > + };
>>>> > +
>>>> > + template<typename _Fn>
>>>> > + struct __func_handle<_Fn, _FunctorType::_MemberPtr>
>>>> > + {
>>>> > + __func_handle() = default;
>>>> > +
>>>> > + constexpr explicit
>>>> > + __func_handle(_Fn __func) noexcept
>>>> > + : _M_ptr(__func)
>>>> > + {}
>>>> > +
>>>> > + template<typename... _Iters>
>>>> > + constexpr decltype(auto)
>>>> > + _M_call_deref(const _Iters&... __iters) const
>>>> > + noexcept(noexcept(std::__invoke(_M_ptr, *__iters...)))
>>>> > + { return std::__invoke(_M_ptr, *__iters...); }
>>>> > +
>>>> > + template<typename _DistType, typename... _Iters>
>>>> > + constexpr decltype(auto)
>>>> > + _M_call_subscript(const _DistType __n, const _Iters&...
>>>> __iters) const
>>>> > + noexcept(noexcept(std::__invoke(_M_ptr,
>>>> __iters[iter_difference_t<_Iters>(__n)]...)))
>>>> > + { return std::__invoke(_M_ptr,
>>>> __iters[iter_difference_t<_Iters>(__n)]...); }
>>>> > +
>>>> > + private:
>>>> > + _Fn _M_ptr = nullptr;
>>>> > + };
>>>> > +
>>>> > + template<typename _Fn>
>>>> > + struct __func_handle<_Fn, _FunctorType::_StaticOperator>
>>>> > + {
>>>> > + __func_handle() = default;
>>>> > +
>>>> > + constexpr explicit
>>>> > + __func_handle(const _Fn&) noexcept
>>>> > + {}
>>>> > +
>>>> > + template<typename... _Iters>
>>>> > + static constexpr decltype(auto)
>>>> > + _M_call_deref(const _Iters&... __iters)
>>>> > + noexcept(noexcept(_Fn::operator()(*__iters...)))
>>>> > + { return _Fn::operator()(*__iters...); }
>>>> > +
>>>> > + template<typename _DistType, typename... _Iters>
>>>> > + static constexpr decltype(auto)
>>>> > + _M_call_subscript(_DistType __n, const _Iters&... __iters)
>>>> > +
>>>> noexcept(noexcept(_Fn::operator()(__iters[iter_difference_t<_Iters>(__n)]...)))
>>>> > + { return
>>>> _Fn::operator()(__iters[iter_difference_t<_Iters>(__n)]...); }
>>>> > + };
>>>> > +
>>>> > + template<typename _Fn, typename... _Iters>
>>>> > + using __func_handle_t = decltype([] {
>>>> > + using _Fd = remove_cv_t<_Fn>;
>>>> > + if constexpr (is_member_pointer_v<_Fd>)
>>>> > + return __func_handle<_Fd, _FunctorType::_MemberPtr>();
>>>> > + else if constexpr (std::is_function_v<remove_pointer_t<_Fd>>)
>>>> > + return __func_handle<_Fd, _FunctorType::_FunctionPtr>();
>>>> > + else if constexpr (requires (const _Iters&... __iters)
>>>> > + { _Fd::operator()(*__iters...); })
>>>> > + return __func_handle<_Fd, _FunctorType::_StaticOperator>();
>>>> > + else
>>>> > + return __func_handle<_Fn, _FunctorType::_Statefull>();
>>>> > + }());
>>>> > } // namespace __detail
>>>> >
>>>> > /// A view that contains exactly one element.
>>>> > @@ -1874,6 +2006,10 @@ namespace views::__adaptor
>>>> > private:
>>>> > using _Parent = __detail::__maybe_const_t<_Const,
>>>> transform_view>;
>>>> > using _Base = transform_view::_Base<_Const>;
>>>> > + using _Base_iter = iterator_t<_Base>;
>>>> > + using _Func_handle = __detail::__func_handle_t<
>>>> > + __detail::__maybe_const_t<_Const, _Fp>,
>>>> > + _Base_iter>;
>>>> >
>>>> > static auto
>>>> > _S_iter_concept()
>>>> > @@ -1888,10 +2024,8 @@ namespace views::__adaptor
>>>> > return input_iterator_tag{};
>>>> > }
>>>> >
>>>> > - using _Base_iter = iterator_t<_Base>;
>>>> > -
>>>> > _Base_iter _M_current = _Base_iter();
>>>> > - _Parent* _M_parent = nullptr;
>>>> > + [[no_unique_address]] _Func_handle _M_fun;
>>>> >
>>>> > public:
>>>> > using iterator_concept = decltype(_S_iter_concept());
>>>> > @@ -1904,16 +2038,20 @@ namespace views::__adaptor
>>>> > _Iterator() requires default_initializable<_Base_iter> =
>>>> default;
>>>> >
>>>> > constexpr
>>>> > - _Iterator(_Parent* __parent, _Base_iter __current)
>>>> > - : _M_current(std::move(__current)),
>>>> > - _M_parent(__parent)
>>>> > + _Iterator(_Func_handle __fun, _Base_iter __current)
>>>> > + : _M_current(std::move(__current)), _M_fun(__fun)
>>>> > { }
>>>> >
>>>> > + constexpr
>>>> > + _Iterator(_Parent* __parent, _Base_iter __current)
>>>> > + : _M_current(std::move(__current)),
>>>> _M_fun(*__parent->_M_fun)
>>>> > + {}
>>>> > +
>>>> > constexpr
>>>> > _Iterator(_Iterator<!_Const> __i)
>>>> > requires _Const
>>>> > && convertible_to<iterator_t<_Vp>, _Base_iter>
>>>> > - : _M_current(std::move(__i._M_current)),
>>>> _M_parent(__i._M_parent)
>>>> > + : _M_current(std::move(__i._M_current)), _M_fun(__i._M_fun)
>>>> > { }
>>>> >
>>>> > constexpr const _Base_iter&
>>>> > @@ -1926,8 +2064,8 @@ namespace views::__adaptor
>>>> >
>>>> > constexpr decltype(auto)
>>>> > operator*() const
>>>> > - noexcept(noexcept(std::__invoke(*_M_parent->_M_fun,
>>>> *_M_current)))
>>>> > - { return std::__invoke(*_M_parent->_M_fun, *_M_current); }
>>>> > + noexcept(noexcept(_M_fun._M_call_deref(_M_current)))
>>>> > + { return _M_fun._M_call_deref(_M_current); }
>>>> >
>>>> > constexpr _Iterator&
>>>> > operator++()
>>>> > @@ -1980,7 +2118,7 @@ namespace views::__adaptor
>>>> > constexpr decltype(auto)
>>>> > operator[](difference_type __n) const
>>>> > requires random_access_range<_Base>
>>>> > - { return std::__invoke(*_M_parent->_M_fun, _M_current[__n]); }
>>>> > + { return _M_fun._M_call_subscript(__n, _M_current); }
>>>> >
>>>> > friend constexpr bool
>>>> > operator==(const _Iterator& __x, const _Iterator& __y)
>>>> > @@ -2018,17 +2156,17 @@ namespace views::__adaptor
>>>> > friend constexpr _Iterator
>>>> > operator+(_Iterator __i, difference_type __n)
>>>> > requires random_access_range<_Base>
>>>> > - { return {__i._M_parent, __i._M_current + __n}; }
>>>> > + { return {__i._M_fun, __i._M_current + __n}; }
>>>> >
>>>> > friend constexpr _Iterator
>>>> > operator+(difference_type __n, _Iterator __i)
>>>> > requires random_access_range<_Base>
>>>> > - { return {__i._M_parent, __i._M_current + __n}; }
>>>> > + { return {__i._M_fun, __i._M_current + __n}; }
>>>> >
>>>> > friend constexpr _Iterator
>>>> > operator-(_Iterator __i, difference_type __n)
>>>> > requires random_access_range<_Base>
>>>> > - { return {__i._M_parent, __i._M_current - __n}; }
>>>> > + { return {__i._M_fun, __i._M_current - __n}; }
>>>> >
>>>> > // _GLIBCXX_RESOLVE_LIB_DEFECTS
>>>> > // 3483. transform_view::iterator's difference is
>>>> overconstrained
>>>> > @@ -5126,13 +5264,21 @@ namespace views::__adaptor
>>>> > class zip_transform_view<_Fp, _Vs...>::_Iterator : public
>>>> __iter_cat<_Const>
>>>> > {
>>>> > using _Parent = __detail::__maybe_const_t<_Const,
>>>> zip_transform_view>;
>>>> > + using _Fun_handle = __detail::__func_handle_t<
>>>> > + __detail::__maybe_const_t<_Const, _Fp>,
>>>> > + iterator_t<__detail::__maybe_const_t<_Const,
>>>> _Vs>>...>;
>>>> >
>>>> > - _Parent* _M_parent = nullptr;
>>>> > + [[no_unique_address]] _Fun_handle _M_fun;
>>>> > __ziperator<_Const> _M_inner;
>>>> >
>>>> > + constexpr
>>>> > + _Iterator(_Fun_handle __fun, __ziperator<_Const> __inner)
>>>> > + : _M_fun(__fun), _M_inner(std::move(__inner))
>>>> > + { }
>>>> > +
>>>> > constexpr
>>>> > _Iterator(_Parent& __parent, __ziperator<_Const> __inner)
>>>> > - : _M_parent(std::__addressof(__parent)),
>>>> _M_inner(std::move(__inner))
>>>> > + : _M_fun(*__parent._M_fun), _M_inner(std::move(__inner))
>>>> > { }
>>>> >
>>>> > friend class zip_transform_view;
>>>> > @@ -5150,14 +5296,14 @@ namespace views::__adaptor
>>>> > constexpr
>>>> > _Iterator(_Iterator<!_Const> __i)
>>>> > requires _Const && convertible_to<__ziperator<false>,
>>>> __ziperator<_Const>>
>>>> > - : _M_parent(__i._M_parent), _M_inner(std::move(__i._M_inner))
>>>> > + : _M_fun(__i._M_fun), _M_inner(std::move(__i._M_inner))
>>>> > { }
>>>> >
>>>> > constexpr decltype(auto)
>>>> > operator*() const
>>>> > {
>>>> > return std::apply([&](const auto&... __iters) ->
>>>> decltype(auto) {
>>>> > - return std::__invoke(*_M_parent->_M_fun, *__iters...);
>>>> > + return _M_fun._M_call_deref(__iters...);
>>>> > }, _M_inner._M_current);
>>>> > }
>>>> >
>>>> > @@ -5213,7 +5359,7 @@ namespace views::__adaptor
>>>> > operator[](difference_type __n) const requires
>>>> random_access_range<_Base<_Const>>
>>>> > {
>>>> > return std::apply([&]<typename... _Is>(const _Is&... __iters)
>>>> -> decltype(auto) {
>>>> > - return std::__invoke(*_M_parent->_M_fun,
>>>> __iters[iter_difference_t<_Is>(__n)]...);
>>>> > + return _M_fun._M_call_subscript(__n, __iters...);
>>>> > }, _M_inner._M_current);
>>>> > }
>>>> >
>>>> > @@ -5230,17 +5376,17 @@ namespace views::__adaptor
>>>> > friend constexpr _Iterator
>>>> > operator+(const _Iterator& __i, difference_type __n)
>>>> > requires random_access_range<_Base<_Const>>
>>>> > - { return _Iterator(*__i._M_parent, __i._M_inner + __n); }
>>>> > + { return _Iterator(__i._M_fun, __i._M_inner + __n); }
>>>> >
>>>> > friend constexpr _Iterator
>>>> > operator+(difference_type __n, const _Iterator& __i)
>>>> > requires random_access_range<_Base<_Const>>
>>>> > - { return _Iterator(*__i._M_parent, __i._M_inner + __n); }
>>>> > + { return _Iterator(__i._M_fun, __i._M_inner + __n); }
>>>> >
>>>> > friend constexpr _Iterator
>>>> > operator-(const _Iterator& __i, difference_type __n)
>>>> > requires random_access_range<_Base<_Const>>
>>>> > - { return _Iterator(*__i._M_parent, __i._M_inner - __n); }
>>>> > + { return _Iterator(__i._M_fun, __i._M_inner - __n); }
>>>> >
>>>> > friend constexpr difference_type
>>>> > operator-(const _Iterator& __x, const _Iterator& __y)
>>>> > @@ -5807,13 +5953,23 @@ namespace views::__adaptor
>>>> > {
>>>> > using _Parent = __detail::__maybe_const_t<_Const,
>>>> adjacent_transform_view>;
>>>> > using _Base = __detail::__maybe_const_t<_Const, _Vp>;
>>>> > + using _Fun_handle = decltype([]<size_t...
>>>> _Ids>(std::index_sequence<_Ids...>) {
>>>> > + return __detail::__func_handle_t<
>>>> > + __detail::__maybe_const_t<_Const,
>>>> _Fp>,
>>>> > +
>>>> iterator_t<__detail::__maybe_const_t<_Const || (_Ids < 0u), _Vp>>...>();
>>>>
>>>> Maybe '(_Ids, _Const)' would be a little less cryptic than
>>>> '_Const || (_Ids < 0u)'?
>>>>
>>> Yes, that is major improvement.
>>>
>>>> Besides that looks good!
>>>>
>>>> > + }(make_index_sequence<_Nm>()));
>>>> >
>>>> > - _Parent* _M_parent = nullptr;
>>>> > + [[no_unique_address]] _Fun_handle _M_fun;
>>>> > _InnerIter<_Const> _M_inner;
>>>> >
>>>> > + constexpr
>>>> > + _Iterator(_Fun_handle __fun, _InnerIter<_Const> __inner)
>>>> > + : _M_fun(__fun), _M_inner(std::move(__inner))
>>>> > + { }
>>>> > +
>>>> > constexpr
>>>> > _Iterator(_Parent& __parent, _InnerIter<_Const> __inner)
>>>> > - : _M_parent(std::__addressof(__parent)),
>>>> _M_inner(std::move(__inner))
>>>> > + : _M_fun(*__parent._M_fun), _M_inner(std::move(__inner))
>>>> > { }
>>>> >
>>>> > static auto
>>>> > @@ -5854,14 +6010,14 @@ namespace views::__adaptor
>>>> > constexpr
>>>> > _Iterator(_Iterator<!_Const> __i)
>>>> > requires _Const && convertible_to<_InnerIter<false>,
>>>> _InnerIter<_Const>>
>>>> > - : _M_parent(__i._M_parent), _M_inner(std::move(__i._M_inner))
>>>> > + : _M_fun(__i._M_fun), _M_inner(std::move(__i._M_inner))
>>>> > { }
>>>> >
>>>> > constexpr decltype(auto)
>>>> > operator*() const
>>>> > {
>>>> > return std::apply([&](const auto&... __iters) ->
>>>> decltype(auto) {
>>>> > - return std::__invoke(*_M_parent->_M_fun, *__iters...);
>>>> > + return _M_fun._M_call_deref(__iters...);
>>>> > }, _M_inner._M_current);
>>>> > }
>>>> >
>>>> > @@ -5913,7 +6069,7 @@ namespace views::__adaptor
>>>> > operator[](difference_type __n) const requires
>>>> random_access_range<_Base>
>>>> > {
>>>> > return std::apply([&](const auto&... __iters) ->
>>>> decltype(auto) {
>>>> > - return std::__invoke(*_M_parent->_M_fun, __iters[__n]...);
>>>> > + return _M_fun._M_call_subscript(__n, __iters...);
>>>> > }, _M_inner._M_current);
>>>> > }
>>>> >
>>>> > @@ -5950,17 +6106,17 @@ namespace views::__adaptor
>>>> > friend constexpr _Iterator
>>>> > operator+(const _Iterator& __i, difference_type __n)
>>>> > requires random_access_range<_Base>
>>>> > - { return _Iterator(*__i._M_parent, __i._M_inner + __n); }
>>>> > + { return _Iterator(__i._M_fun, __i._M_inner + __n); }
>>>> >
>>>> > friend constexpr _Iterator
>>>> > operator+(difference_type __n, const _Iterator& __i)
>>>> > requires random_access_range<_Base>
>>>> > - { return _Iterator(*__i._M_parent, __i._M_inner + __n); }
>>>> > + { return _Iterator(__i._M_fun, __i._M_inner + __n); }
>>>> >
>>>> > friend constexpr _Iterator
>>>> > operator-(const _Iterator& __i, difference_type __n)
>>>> > requires random_access_range<_Base>
>>>> > - { return _Iterator(*__i._M_parent, __i._M_inner - __n); }
>>>> > + { return _Iterator(__i._M_fun, __i._M_inner - __n); }
>>>> >
>>>> > friend constexpr difference_type
>>>> > operator-(const _Iterator& __x, const _Iterator& __y)
>>>> > diff --git
>>>> a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc
>>>> b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc
>>>> > index 772e4b3b6a0..1667c6250c5 100644
>>>> > ---
>>>> a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc
>>>> > +++
>>>> b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc
>>>> > @@ -113,6 +113,97 @@ test04()
>>>> > static_assert( requires { x |
>>>> views::pairwise_transform(move_only{}); } );
>>>> > }
>>>> >
>>>> > +struct X
>>>> > +{
>>>> > + int i,j;
>>>> > + constexpr int combine(X o) const
>>>> > + { return i + o.j; }
>>>> > +};
>>>> > +
>>>> > +template<size_t FuncSize, typename Fn>
>>>> > +constexpr bool
>>>> > +test05(Fn f)
>>>> > +{
>>>> > + using namespace __gnu_test;
>>>> > + X x[] = {{1,500},{2,400},{3,300},{4,200},{5,100}};
>>>> > + test_range<X, random_access_iterator_wrapper> rx(x);
>>>> > +
>>>> > + auto v = rx | views::pairwise_transform(f);
>>>> > + VERIFY( ranges::size(v) == 4 );
>>>> > + VERIFY( ranges::distance(v.begin(), v.end()) == 4 );
>>>> > + VERIFY( ranges::equal(v, (int[]){401,302,203,104}) );
>>>> > + VERIFY( ranges::equal(v | views::reverse,
>>>> (int[]){104,203,302,401}) );
>>>> > + using R = decltype(v);
>>>> > + using It = ranges::iterator_t<R>;
>>>> > + static_assert(std::same_as<int, decltype(*ranges::begin(v))>);
>>>> > + static_assert(std::same_as<int, std::iter_value_t<It>>);
>>>> > + static_assert(sizeof(It) == 2*sizeof(rx.begin()) + FuncSize);
>>>> > + static_assert(ranges::view<R>);
>>>> > + static_assert(ranges::sized_range<R>);
>>>> > + static_assert(!ranges::common_range<R>);
>>>> > + static_assert(ranges::random_access_range<R>);
>>>> > + return true;
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05a()
>>>> > +{
>>>> > + auto comb = [](const X& x1, const X& x2) { return x1.i + x2.j; };
>>>> > + return test05<sizeof(void*)>(comb);
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05b()
>>>> > +{
>>>> > + auto comb = [](const X& x1, const X& x2) static { return x1.i +
>>>> x2.j; };
>>>> > + return test05<0>(comb);
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05c()
>>>> > +{
>>>> > + int(*comb)(const X&, const X&) = [](const X& x1, const X& x2) {
>>>> return x1.i + x2.j; };
>>>> > + return test05<sizeof(void(*)())>(comb);
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05d()
>>>> > +{
>>>> > + return test05<sizeof(int(X::*)())>(&X::combine);
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05e()
>>>> > +{
>>>> > + struct PickStatic
>>>> > + {
>>>> > + static constexpr int
>>>> > + operator()(const X& x1, const X& x2)
>>>> > + { return x1.i + x2.j; }
>>>> > +
>>>> > + constexpr int
>>>> > + operator()(int x, int y) const
>>>> > + { return x + y; };
>>>> > + };
>>>> > + return test05<0>(PickStatic{});
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05f()
>>>> > +{
>>>> > + struct PickObject
>>>> > + {
>>>> > + constexpr int
>>>> > + operator()(const X& x1, const X& x2) const
>>>> > + { return x1.i + x2.j; }
>>>> > +
>>>> > + static constexpr int
>>>> > + operator()(int x, int y)
>>>> > + { return x + y; };
>>>> > + };
>>>> > + return test05<sizeof(void*)>(PickObject{});
>>>> > +}
>>>> > +
>>>> > int
>>>> > main()
>>>> > {
>>>> > @@ -120,4 +211,10 @@ main()
>>>> > static_assert(test02());
>>>> > static_assert(test03());
>>>> > test04();
>>>> > + static_assert(test05a());
>>>> > + static_assert(test05b());
>>>> > + static_assert(test05c());
>>>> > + static_assert(test05d());
>>>> > + static_assert(test05e());
>>>> > + static_assert(test05f());
>>>> > }
>>>> > diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
>>>> b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
>>>> > index 1788db1ce8d..c6d6b916730 100644
>>>> > --- a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
>>>> > +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
>>>> > @@ -28,12 +28,12 @@ using __gnu_test::random_access_iterator_wrapper;
>>>> > namespace ranges = std::ranges;
>>>> > namespace views = std::ranges::views;
>>>> >
>>>> > +template<typename Fn>
>>>> > void
>>>> > -test01()
>>>> > +test01(Fn f)
>>>> > {
>>>> > int x[] = {1,2,3,4,5};
>>>> > - auto is_odd = [] (int i) { return i%2==1; };
>>>> > - auto v = x | views::transform(is_odd);
>>>> > + auto v = x | views::transform(f);
>>>> > VERIFY( ranges::equal(v, (int[]){1,0,1,0,1}) );
>>>> > using R = decltype(v);
>>>> > static_assert(std::same_as<bool, decltype(*ranges::begin(v))>);
>>>> > @@ -42,30 +42,124 @@ test01()
>>>> > static_assert(ranges::random_access_range<R>);
>>>> > }
>>>> >
>>>> > +void
>>>> > +test01a()
>>>> > +{
>>>> > + auto is_odd = [] (int i) { return i%2==1; };
>>>> > + test01(is_odd);
>>>> > +}
>>>> > +
>>>> > +void
>>>> > +test01b()
>>>> > +{
>>>> > +#if __cpp_static_call_operator >= 202207L
>>>> > + auto is_odd = [] (int i) static { return i%2==1; };
>>>> > + test01(is_odd);
>>>> > +#endif
>>>> > +}
>>>> > +
>>>> > +void
>>>> > +test01c()
>>>> > +{
>>>> > + bool(*is_odd)(int) = [] (int i) { return i%2==1; };
>>>> > + test01(is_odd);
>>>> > +}
>>>> > +
>>>> > struct X
>>>> > {
>>>> > int i,j;
>>>> > + int& first() { return i; }
>>>> > };
>>>> >
>>>> > +template<size_t FuncSize, typename Fn>
>>>> > void
>>>> > -test02()
>>>> > +test02(Fn f)
>>>> > {
>>>> > X x[] = {{1,2},{3,4},{5,6},{7,8},{9,10}};
>>>> > test_range<X, random_access_iterator_wrapper> rx(x);
>>>> > - auto v = rx | views::transform(&X::i);
>>>> > + auto v = rx | views::transform(f);
>>>> > VERIFY( ranges::size(v) == 5 );
>>>> > VERIFY( ranges::distance(v.begin(), v.end()) == 5 );
>>>> > VERIFY( ranges::equal(v, (int[]){1,3,5,7,9}) );
>>>> > VERIFY( ranges::equal(v | views::reverse, (int[]){9,7,5,3,1}) );
>>>> > using R = decltype(v);
>>>> > + using It = ranges::iterator_t<R>;
>>>> > static_assert(std::same_as<int&, decltype(*ranges::begin(v))>);
>>>> > - static_assert(std::same_as<int,
>>>> std::iter_value_t<ranges::iterator_t<R>>>);
>>>> > + static_assert(std::same_as<int, std::iter_value_t<It>>);
>>>> > + static_assert(sizeof(It) == sizeof(rx.begin()) + FuncSize);
>>>> > static_assert(ranges::view<R>);
>>>> > static_assert(ranges::sized_range<R>);
>>>> > static_assert(!ranges::common_range<R>);
>>>> > static_assert(ranges::random_access_range<R>);
>>>> > }
>>>> >
>>>> > +void
>>>> > +test02a()
>>>> > +{ test02<sizeof(int X::*)>(&X::i); }
>>>> > +
>>>> > +void
>>>> > +test02b()
>>>> > +{ test02<sizeof(int(X::*)())>(&X::first); }
>>>> > +
>>>> > +void
>>>> > +test02c()
>>>> > +{
>>>> > + auto first = [](X& x) -> int& { return x.i; };
>>>> > + test02<sizeof(void*)>(first);
>>>> > +}
>>>> > +
>>>> > +void
>>>> > +test02d()
>>>> > +{
>>>> > +#if __cpp_static_call_operator >= 202207L
>>>> > + auto first = [](X& x) static -> int& { return x.i; };
>>>> > + test02<0>(first);
>>>> > +#endif
>>>> > +}
>>>> > +
>>>> > +void
>>>> > +test02e()
>>>> > +{
>>>> > + int&(*fptr)(X&) = [](X& x) -> int& { return x.i; };
>>>> > + test02<sizeof(void(*)())>(fptr);
>>>> > +}
>>>> > +
>>>> > +void
>>>> > +test02f()
>>>> > +{
>>>> > +#if __cpp_static_call_operator >= 202207L
>>>> > + struct PickStatic
>>>> > + {
>>>> > + static constexpr int&
>>>> > + operator()(X& x)
>>>> > + { return x.i; }
>>>> > +
>>>> > + constexpr int
>>>> > + operator()(char*) const
>>>> > + { return 0; };
>>>> > + };
>>>> > + test02<0>(PickStatic{});
>>>> > +#endif
>>>> > +}
>>>> > +
>>>> > +void
>>>> > +test02g()
>>>> > +{
>>>> > +#if __cpp_static_call_operator >= 202207L
>>>> > + struct PickObject
>>>> > + {
>>>> > + constexpr int&
>>>> > + operator()(X& x) const
>>>> > + { return x.i; }
>>>> > +
>>>> > + static constexpr int
>>>> > + operator()(char*)
>>>> > + { return 0; };
>>>> > + };
>>>> > + test02<sizeof(void*)>(PickObject{});
>>>> > +#endif
>>>> > +}
>>>> > +
>>>> > void
>>>> > test03()
>>>> > {
>>>> > @@ -230,8 +324,16 @@ test11()
>>>> > int
>>>> > main()
>>>> > {
>>>> > - test01();
>>>> > - test02();
>>>> > + test01a();
>>>> > + test01b();
>>>> > + test01c();
>>>> > + test02a();
>>>> > + test02b();
>>>> > + test02c();
>>>> > + test02d();
>>>> > + test02e();
>>>> > + test02f();
>>>> > + test02g();
>>>> > test03();
>>>> > test04();
>>>> > test05();
>>>> > diff --git a/libstdc++-v3/testsuite/std/ranges/zip_transform/1.cc
>>>> b/libstdc++-v3/testsuite/std/ranges/zip_transform/1.cc
>>>> > index 9a0ad3814e6..d4bd7db26cb 100644
>>>> > --- a/libstdc++-v3/testsuite/std/ranges/zip_transform/1.cc
>>>> > +++ b/libstdc++-v3/testsuite/std/ranges/zip_transform/1.cc
>>>> > @@ -132,6 +132,97 @@ test04()
>>>> > static_assert( requires { views::zip_transform(move_only{}, x, x);
>>>> } );
>>>> > }
>>>> >
>>>> > +struct X
>>>> > +{
>>>> > + int i;
>>>> > + constexpr int add(int b) const
>>>> > + { return i+b; }
>>>> > +};
>>>> > +
>>>> > +template<size_t ExtraSize, typename Fn>
>>>> > +constexpr bool
>>>> > +test05(Fn f)
>>>> > +{
>>>> > + using namespace __gnu_test;
>>>> > + X x[] = {{1},{2},{3},{4},{5}};
>>>> > + int y[] = {500,400,300,200,100};
>>>> > + test_range<X, random_access_iterator_wrapper> rx(x);
>>>> > + test_range<int, random_access_iterator_wrapper> ry(y);
>>>> > +
>>>> > + auto v = views::zip_transform(f, rx, ry);
>>>> > + VERIFY( ranges::size(v) == 5 );
>>>> > + VERIFY( ranges::distance(v.begin(), v.end()) == 5 );
>>>> > + VERIFY( ranges::equal(v, (int[]){501,402,303,204,105}) );
>>>> > + VERIFY( ranges::equal(v | views::reverse,
>>>> (int[]){105,204,303,402,501}) );
>>>> > + using R = decltype(v);
>>>> > + using It = ranges::iterator_t<R>;
>>>> > + static_assert(std::same_as<int, decltype(*ranges::begin(v))>);
>>>> > + static_assert(std::same_as<int, std::iter_value_t<It>>);
>>>> > + static_assert(sizeof(It) == sizeof(rx.begin()) +
>>>> sizeof(ry.begin()) + ExtraSize);
>>>> > + static_assert(ranges::view<R>);
>>>> > + static_assert(ranges::sized_range<R>);
>>>> > + static_assert(ranges::common_range<R>);
>>>> > + static_assert(ranges::random_access_range<R>);
>>>> > + return true;
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05a()
>>>> > +{
>>>> > + auto add = [](const X& x, int v) { return x.i + v; };
>>>> > + return test05<sizeof(void*)>(add);
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05b()
>>>> > +{
>>>> > + auto add = [](const X& x, int v) static { return x.i + v; };
>>>> > + return test05<0>(add);
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05c()
>>>> > +{
>>>> > + int(*ptr)(const X&, int) = [](const X& x, int v) { return x.i + v;
>>>> };
>>>> > + return test05<sizeof(void(*)())>(ptr);
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05d()
>>>> > +{ return test05<sizeof(int(X::*)())>(&X::add); }
>>>> > +
>>>> > +constexpr bool
>>>> > +test05e()
>>>> > +{
>>>> > + struct PickStatic
>>>> > + {
>>>> > + static constexpr int
>>>> > + operator()(const X& x1, int v)
>>>> > + { return x1.i + v; }
>>>> > +
>>>> > + constexpr int
>>>> > + operator()(int x, int y) const
>>>> > + { return x + y; };
>>>> > + };
>>>> > + return test05<0>(PickStatic{});
>>>> > +}
>>>> > +
>>>> > +constexpr bool
>>>> > +test05f()
>>>> > +{
>>>> > + struct PickObject
>>>> > + {
>>>> > + constexpr int
>>>> > + operator()(const X& x1, int v) const
>>>> > + { return x1.i + v; }
>>>> > +
>>>> > + static constexpr int
>>>> > + operator()(int x, int y)
>>>> > + { return x + y; };
>>>> > + };
>>>> > + return test05<sizeof(void*)>(PickObject{});
>>>> > +}
>>>> > +
>>>> > int
>>>> > main()
>>>> > {
>>>> > @@ -139,4 +230,14 @@ main()
>>>> > static_assert(test02());
>>>> > static_assert(test03());
>>>> > test04();
>>>> > + static_assert(test01());
>>>> > + static_assert(test02());
>>>> > + static_assert(test03());
>>>> > + test04();
>>>> > + static_assert(test05a());
>>>> > + static_assert(test05b());
>>>> > + static_assert(test05c());
>>>> > + static_assert(test05d());
>>>> > + static_assert(test05e());
>>>> > + static_assert(test05f());
>>>> > }
>>>> > --
>>>> > 2.51.0
>>>> >
>>>> >
>>>
>>>
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