* [PATCH] libstdc++: extraneous begin in cartesian_product_view::end [PR107572] @ 2023-03-07 20:13 Patrick Palka 2023-03-07 20:49 ` Patrick Palka 0 siblings, 1 reply; 3+ messages in thread From: Patrick Palka @ 2023-03-07 20:13 UTC (permalink / raw) To: gcc-patches; +Cc: libstdc++, Patrick Palka ranges::begin() isn't guaranteed to be equality-preserving for non-forward ranges, so in cartesian_product_view::end we need to be careful about calling begin() on the first range (which could be non-forward) in the (non-degenerate) case where __empty_tail is false. Since we're already using a variadic lambda to compute __empty_tail, we might as well use that same lambda to build up the tuple of iterators instead of doing it via __tuple_transform. Tested on x86_64-pc-linux-gnu, does this look OK for trunk? PR libstdc++/107572 libstdc++-v3/ChangeLog: * include/std/ranges (cartesian_product_view::end): When building the tuple of iterators, avoid calling ranges::begin on the first range if __empty_tail is false. * testsuite/std/ranges/cartesian_product/1.cc (test07): New test. --- libstdc++-v3/include/std/ranges | 36 +++++++++++++------ .../std/ranges/cartesian_product/1.cc | 22 ++++++++++++ 2 files changed, 48 insertions(+), 10 deletions(-) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index e0cac15a64f..0de7bdef504 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -8078,26 +8078,42 @@ namespace views::__adaptor end() requires ((!__detail::__simple_view<_First> || ... || !__detail::__simple_view<_Vs>) && __detail::__cartesian_product_is_common<_First, _Vs...>) { - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto& __first = std::get<0>(_M_bases); + auto __first_it = __empty_tail + ? ranges::begin(__first) + : __detail::__cartesian_common_arg_end(__first); + // N.B. When implementing P2165R4 this should be changed to always return tuple. + if constexpr (sizeof...(_Is) == 1) + return std::make_pair(std::move(__first_it), + ranges::begin(std::get<1 + _Is>(_M_bases))...); + else + return std::make_tuple(std::move(__first_it), + ranges::begin(std::get<1 + _Is>(_M_bases))...); }(make_index_sequence<sizeof...(_Vs)>{}); - auto __it = __detail::__tuple_transform(ranges::begin, _M_bases); - if (!__empty_tail) - std::get<0>(__it) = __detail::__cartesian_common_arg_end(std::get<0>(_M_bases)); return _Iterator<false>{*this, std::move(__it)}; } constexpr _Iterator<true> end() const requires __detail::__cartesian_product_is_common<const _First, const _Vs...> { - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto& __first = std::get<0>(_M_bases); + auto __first_it = __empty_tail + ? ranges::begin(__first) + : __detail::__cartesian_common_arg_end(__first); + // N.B. When implementing P2165R4 this should be changed to always return tuple. + if constexpr (sizeof...(_Is) == 1) + return std::make_pair(std::move(__first_it), + ranges::begin(std::get<1 + _Is>(_M_bases))...); + else + return std::make_tuple(std::move(__first_it), + ranges::begin(std::get<1 + _Is>(_M_bases))...); }(make_index_sequence<sizeof...(_Vs)>{}); - auto __it = __detail::__tuple_transform(ranges::begin, _M_bases); - if (!__empty_tail) - std::get<0>(__it) = __detail::__cartesian_common_arg_end(std::get<0>(_M_bases)); return _Iterator<true>{*this, std::move(__it)}; } diff --git a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc index 1ec4422e6f3..34639f514aa 100644 --- a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc +++ b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc @@ -3,6 +3,7 @@ #include <ranges> #include <algorithm> +#include <sstream> #include <testsuite_hooks.h> #include <testsuite_iterators.h> @@ -178,6 +179,26 @@ test06() return true; } +void +test07() +{ + // PR libstdc++/107572 + static std::istringstream ints("0 1 2 3 4"); + struct istream_range + { + auto begin() { return std::istream_iterator<int>{ints}; } + auto end() { return std::istream_iterator<int>{}; } + }; + istream_range r; + int i = 0; + for (auto [v] : views::cartesian_product(r)) + { + VERIFY( v == i ); + ++i; + }; + VERIFY( i == 5 ); +} + int main() { @@ -187,4 +208,5 @@ main() test04(); test05(); static_assert(test06()); + test07(); } -- 2.40.0.rc0.57.g454dfcbddf ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] libstdc++: extraneous begin in cartesian_product_view::end [PR107572] 2023-03-07 20:13 [PATCH] libstdc++: extraneous begin in cartesian_product_view::end [PR107572] Patrick Palka @ 2023-03-07 20:49 ` Patrick Palka 2023-03-09 17:59 ` Jonathan Wakely 0 siblings, 1 reply; 3+ messages in thread From: Patrick Palka @ 2023-03-07 20:49 UTC (permalink / raw) To: Patrick Palka; +Cc: gcc-patches, libstdc++ On Tue, 7 Mar 2023, Patrick Palka wrote: > ranges::begin() isn't guaranteed to be equality-preserving for > non-forward ranges, so in cartesian_product_view::end we need to be > careful about calling begin() on the first range (which could be > non-forward) in the (non-degenerate) case where __empty_tail is false. > > Since we're already using a variadic lambda to compute __empty_tail, we > might as well use that same lambda to build up the tuple of iterators > instead of doing it via __tuple_transform. > > Tested on x86_64-pc-linux-gnu, does this look OK for trunk? > > PR libstdc++/107572 > > libstdc++-v3/ChangeLog: > > * include/std/ranges (cartesian_product_view::end): When > building the tuple of iterators, avoid calling ranges::begin on > the first range if __empty_tail is false. > * testsuite/std/ranges/cartesian_product/1.cc (test07): New test. > --- > libstdc++-v3/include/std/ranges | 36 +++++++++++++------ > .../std/ranges/cartesian_product/1.cc | 22 ++++++++++++ > 2 files changed, 48 insertions(+), 10 deletions(-) > > diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges > index e0cac15a64f..0de7bdef504 100644 > --- a/libstdc++-v3/include/std/ranges > +++ b/libstdc++-v3/include/std/ranges > @@ -8078,26 +8078,42 @@ namespace views::__adaptor > end() requires ((!__detail::__simple_view<_First> || ... || !__detail::__simple_view<_Vs>) > && __detail::__cartesian_product_is_common<_First, _Vs...>) > { > - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { > - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { > + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > + auto& __first = std::get<0>(_M_bases); > + auto __first_it = __empty_tail > + ? ranges::begin(__first) > + : __detail::__cartesian_common_arg_end(__first); > + // N.B. When implementing P2165R4 this should be changed to always return tuple. > + if constexpr (sizeof...(_Is) == 1) > + return std::make_pair(std::move(__first_it), > + ranges::begin(std::get<1 + _Is>(_M_bases))...); > + else > + return std::make_tuple(std::move(__first_it), > + ranges::begin(std::get<1 + _Is>(_M_bases))...); On second thought, it might be better to use __tuple_or_pair_t here instead of manually determining whether to use a pair or tuple, so that we don't forget to adjust this site when implementing P2165R4 (which removes __tuple_or_pair_t): -- >8 -- Subject: [PATCH] libstdc++: extraneous begin in cartesian_product_view::end [PR107572] ranges::begin() isn't guaranteed to be equality-preserving for non-forward ranges, so in cartesian_product_view::end we need to avoid calling begin() on the first range (which could be non-forward) in the (non-degenerate) case where __empty_tail is false. Since we're already using a variadic lambda to compute __empty_tail, we might as well use that same lambda to build up the tuple of iterators instead of doing it separately via __tuple_transform. Tested on x86_64-pc-linux-gnu, does this look OK for trunk? PR libstdc++/107572 libstdc++-v3/ChangeLog: * include/std/ranges (cartesian_product_view::end): When building the tuple of iterators, avoid calling ranges::begin on the first range if __empty_tail is false. * testsuite/std/ranges/cartesian_product/1.cc (test07): New test. --- libstdc++-v3/include/std/ranges | 28 ++++++++++++------- .../std/ranges/cartesian_product/1.cc | 25 +++++++++++++++++ 2 files changed, 43 insertions(+), 10 deletions(-) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index e0cac15a64f..d2ab79179ca 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -8078,26 +8078,34 @@ namespace views::__adaptor end() requires ((!__detail::__simple_view<_First> || ... || !__detail::__simple_view<_Vs>) && __detail::__cartesian_product_is_common<_First, _Vs...>) { - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { + using _Ret = __detail::__tuple_or_pair_t<iterator_t<_First>, + iterator_t<_Vs>...>; + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto& __first = std::get<0>(_M_bases); + return _Ret{(__empty_tail + ? ranges::begin(__first) + : __detail::__cartesian_common_arg_end(__first)), + ranges::begin(std::get<1 + _Is>(_M_bases))...}; }(make_index_sequence<sizeof...(_Vs)>{}); - auto __it = __detail::__tuple_transform(ranges::begin, _M_bases); - if (!__empty_tail) - std::get<0>(__it) = __detail::__cartesian_common_arg_end(std::get<0>(_M_bases)); return _Iterator<false>{*this, std::move(__it)}; } constexpr _Iterator<true> end() const requires __detail::__cartesian_product_is_common<const _First, const _Vs...> { - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { + using _Ret = __detail::__tuple_or_pair_t<iterator_t<const _First>, + iterator_t<const _Vs>...>; + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); + auto& __first = std::get<0>(_M_bases); + return _Ret{(__empty_tail + ? ranges::begin(__first) + : __detail::__cartesian_common_arg_end(__first)), + ranges::begin(std::get<1 + _Is>(_M_bases))...}; }(make_index_sequence<sizeof...(_Vs)>{}); - auto __it = __detail::__tuple_transform(ranges::begin, _M_bases); - if (!__empty_tail) - std::get<0>(__it) = __detail::__cartesian_common_arg_end(std::get<0>(_M_bases)); return _Iterator<true>{*this, std::move(__it)}; } diff --git a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc index 1ec4422e6f3..8069eb0ab3c 100644 --- a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc +++ b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc @@ -3,6 +3,7 @@ #include <ranges> #include <algorithm> +#include <sstream> #include <testsuite_hooks.h> #include <testsuite_iterators.h> @@ -178,6 +179,29 @@ test06() return true; } +void +test07() +{ + // PR libstdc++/107572 + static std::istringstream ints("0 1 2 3 4"); + struct istream_range + { + auto begin() { return std::istream_iterator<int>{ints}; } + auto end() { return std::istream_iterator<int>{}; } + using iterator_concept = std::input_iterator_tag; + }; + static_assert(!ranges::forward_range<istream_range> + && ranges::common_range<istream_range>); + istream_range r; + int i = 0; + for (auto [v] : views::cartesian_product(r)) + { + VERIFY( v == i ); + ++i; + }; + VERIFY( i == 5 ); +} + int main() { @@ -187,4 +211,5 @@ main() test04(); test05(); static_assert(test06()); + test07(); } -- 2.40.0.rc0.57.g454dfcbddf ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] libstdc++: extraneous begin in cartesian_product_view::end [PR107572] 2023-03-07 20:49 ` Patrick Palka @ 2023-03-09 17:59 ` Jonathan Wakely 0 siblings, 0 replies; 3+ messages in thread From: Jonathan Wakely @ 2023-03-09 17:59 UTC (permalink / raw) To: Patrick Palka; +Cc: gcc-patches, libstdc++ On Tue, 7 Mar 2023 at 20:49, Patrick Palka via Libstdc++ <libstdc++@gcc.gnu.org> wrote: > > On Tue, 7 Mar 2023, Patrick Palka wrote: > > > ranges::begin() isn't guaranteed to be equality-preserving for > > non-forward ranges, so in cartesian_product_view::end we need to be > > careful about calling begin() on the first range (which could be > > non-forward) in the (non-degenerate) case where __empty_tail is false. > > > > Since we're already using a variadic lambda to compute __empty_tail, we > > might as well use that same lambda to build up the tuple of iterators > > instead of doing it via __tuple_transform. > > > > Tested on x86_64-pc-linux-gnu, does this look OK for trunk? > > > > PR libstdc++/107572 > > > > libstdc++-v3/ChangeLog: > > > > * include/std/ranges (cartesian_product_view::end): When > > building the tuple of iterators, avoid calling ranges::begin on > > the first range if __empty_tail is false. > > * testsuite/std/ranges/cartesian_product/1.cc (test07): New test. > > --- > > libstdc++-v3/include/std/ranges | 36 +++++++++++++------ > > .../std/ranges/cartesian_product/1.cc | 22 ++++++++++++ > > 2 files changed, 48 insertions(+), 10 deletions(-) > > > > diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges > > index e0cac15a64f..0de7bdef504 100644 > > --- a/libstdc++-v3/include/std/ranges > > +++ b/libstdc++-v3/include/std/ranges > > @@ -8078,26 +8078,42 @@ namespace views::__adaptor > > end() requires ((!__detail::__simple_view<_First> || ... || !__detail::__simple_view<_Vs>) > > && __detail::__cartesian_product_is_common<_First, _Vs...>) > > { > > - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { > > - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > > + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { > > + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > > + auto& __first = std::get<0>(_M_bases); > > + auto __first_it = __empty_tail > > + ? ranges::begin(__first) > > + : __detail::__cartesian_common_arg_end(__first); > > + // N.B. When implementing P2165R4 this should be changed to always return tuple. > > + if constexpr (sizeof...(_Is) == 1) > > + return std::make_pair(std::move(__first_it), > > + ranges::begin(std::get<1 + _Is>(_M_bases))...); > > + else > > + return std::make_tuple(std::move(__first_it), > > + ranges::begin(std::get<1 + _Is>(_M_bases))...); > > On second thought, it might be better to use __tuple_or_pair_t here > instead of manually determining whether to use a pair or tuple, so that > we don't forget to adjust this site when implementing P2165R4 (which > removes __tuple_or_pair_t): Good idea. OK for trunk. > > -- >8 -- > > Subject: [PATCH] libstdc++: extraneous begin in cartesian_product_view::end > [PR107572] > > ranges::begin() isn't guaranteed to be equality-preserving for > non-forward ranges, so in cartesian_product_view::end we need to avoid > calling begin() on the first range (which could be non-forward) in the > (non-degenerate) case where __empty_tail is false. > > Since we're already using a variadic lambda to compute __empty_tail, we > might as well use that same lambda to build up the tuple of iterators > instead of doing it separately via __tuple_transform. > > Tested on x86_64-pc-linux-gnu, does this look OK for trunk? > > PR libstdc++/107572 > > libstdc++-v3/ChangeLog: > > * include/std/ranges (cartesian_product_view::end): When > building the tuple of iterators, avoid calling ranges::begin on > the first range if __empty_tail is false. > * testsuite/std/ranges/cartesian_product/1.cc (test07): New test. > --- > libstdc++-v3/include/std/ranges | 28 ++++++++++++------- > .../std/ranges/cartesian_product/1.cc | 25 +++++++++++++++++ > 2 files changed, 43 insertions(+), 10 deletions(-) > > diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges > index e0cac15a64f..d2ab79179ca 100644 > --- a/libstdc++-v3/include/std/ranges > +++ b/libstdc++-v3/include/std/ranges > @@ -8078,26 +8078,34 @@ namespace views::__adaptor > end() requires ((!__detail::__simple_view<_First> || ... || !__detail::__simple_view<_Vs>) > && __detail::__cartesian_product_is_common<_First, _Vs...>) > { > - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { > - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { > + using _Ret = __detail::__tuple_or_pair_t<iterator_t<_First>, > + iterator_t<_Vs>...>; > + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > + auto& __first = std::get<0>(_M_bases); > + return _Ret{(__empty_tail > + ? ranges::begin(__first) > + : __detail::__cartesian_common_arg_end(__first)), > + ranges::begin(std::get<1 + _Is>(_M_bases))...}; > }(make_index_sequence<sizeof...(_Vs)>{}); > > - auto __it = __detail::__tuple_transform(ranges::begin, _M_bases); > - if (!__empty_tail) > - std::get<0>(__it) = __detail::__cartesian_common_arg_end(std::get<0>(_M_bases)); > return _Iterator<false>{*this, std::move(__it)}; > } > > constexpr _Iterator<true> > end() const requires __detail::__cartesian_product_is_common<const _First, const _Vs...> > { > - bool __empty_tail = [this]<size_t... _Is>(index_sequence<_Is...>) { > - return (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > + auto __it = [this]<size_t... _Is>(index_sequence<_Is...>) { > + using _Ret = __detail::__tuple_or_pair_t<iterator_t<const _First>, > + iterator_t<const _Vs>...>; > + bool __empty_tail = (ranges::empty(std::get<1 + _Is>(_M_bases)) || ...); > + auto& __first = std::get<0>(_M_bases); > + return _Ret{(__empty_tail > + ? ranges::begin(__first) > + : __detail::__cartesian_common_arg_end(__first)), > + ranges::begin(std::get<1 + _Is>(_M_bases))...}; > }(make_index_sequence<sizeof...(_Vs)>{}); > > - auto __it = __detail::__tuple_transform(ranges::begin, _M_bases); > - if (!__empty_tail) > - std::get<0>(__it) = __detail::__cartesian_common_arg_end(std::get<0>(_M_bases)); > return _Iterator<true>{*this, std::move(__it)}; > } > > diff --git a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc > index 1ec4422e6f3..8069eb0ab3c 100644 > --- a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc > +++ b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc > @@ -3,6 +3,7 @@ > > #include <ranges> > #include <algorithm> > +#include <sstream> > #include <testsuite_hooks.h> > #include <testsuite_iterators.h> > > @@ -178,6 +179,29 @@ test06() > return true; > } > > +void > +test07() > +{ > + // PR libstdc++/107572 > + static std::istringstream ints("0 1 2 3 4"); > + struct istream_range > + { > + auto begin() { return std::istream_iterator<int>{ints}; } > + auto end() { return std::istream_iterator<int>{}; } > + using iterator_concept = std::input_iterator_tag; > + }; > + static_assert(!ranges::forward_range<istream_range> > + && ranges::common_range<istream_range>); > + istream_range r; > + int i = 0; > + for (auto [v] : views::cartesian_product(r)) > + { > + VERIFY( v == i ); > + ++i; > + }; > + VERIFY( i == 5 ); > +} > + > int > main() > { > @@ -187,4 +211,5 @@ main() > test04(); > test05(); > static_assert(test06()); > + test07(); > } > -- > 2.40.0.rc0.57.g454dfcbddf > ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-03-09 17:59 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-03-07 20:13 [PATCH] libstdc++: extraneous begin in cartesian_product_view::end [PR107572] Patrick Palka 2023-03-07 20:49 ` Patrick Palka 2023-03-09 17:59 ` Jonathan Wakely
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