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| author | Patrick Palka <ppalka@redhat.com> | 2021-06-17 09:46:07 -0400 |
|---|---|---|
| committer | Patrick Palka <ppalka@redhat.com> | 2021-06-17 09:46:07 -0400 |
| commit | 2b87f3318cf6334a3a42dcf27f2fdec0fce04665 (patch) | |
| tree | 78afc686951f29d137c7725b3d71d345885645b6 | |
| parent | 0f4a2fb44dad6c9c140226fc19ed16109b85e6f4 (diff) | |
| download | gcc-2b87f3318cf6334a3a42dcf27f2fdec0fce04665.zip gcc-2b87f3318cf6334a3a42dcf27f2fdec0fce04665.tar.gz gcc-2b87f3318cf6334a3a42dcf27f2fdec0fce04665.tar.bz2 | |
libstdc++: Non-triv-copyable extra args aren't simple [PR100940]
This force-enables perfect forwarding call wrapper semantics whenever
the extra arguments of a partially applied range adaptor aren't all
trivially copyable, so as to avoid incurring unnecessary copies of
potentially expensive-to-copy objects (such as std::function objects)
when invoking the adaptor.
PR libstdc++/100940
libstdc++-v3/ChangeLog:
* include/std/ranges (__adaptor::_Partial): For the "simple"
forwarding partial specializations, also require that
the extra arguments are trivially copyable.
* testsuite/std/ranges/adaptors/100577.cc (test04): New test.
| -rw-r--r-- | libstdc++-v3/include/std/ranges | 8 | ||||
| -rw-r--r-- | libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc | 14 |
2 files changed, 19 insertions, 3 deletions
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index a428900..73c35da 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -896,11 +896,12 @@ namespace views::__adaptor }; // Partial specialization of the primary template for the case where the extra - // arguments of the adaptor can always be safely forwarded by const reference. - // This lets us get away with a single operator() overload, which makes - // overload resolution failure diagnostics more concise. + // arguments of the adaptor can always be safely and efficiently forwarded by + // const reference. This lets us get away with a single operator() overload, + // which makes overload resolution failure diagnostics more concise. template<typename _Adaptor, typename... _Args> requires __adaptor_has_simple_extra_args<_Adaptor, _Args...> + && (is_trivially_copyable_v<_Args> && ...) struct _Partial<_Adaptor, _Args...> : _RangeAdaptorClosure { tuple<_Args...> _M_args; @@ -930,6 +931,7 @@ namespace views::__adaptor // where _Adaptor accepts a single extra argument. template<typename _Adaptor, typename _Arg> requires __adaptor_has_simple_extra_args<_Adaptor, _Arg> + && is_trivially_copyable_v<_Arg> struct _Partial<_Adaptor, _Arg> : _RangeAdaptorClosure { _Arg _M_arg; diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc index 8ef0846..06be498 100644 --- a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc @@ -21,6 +21,7 @@ // PR libstdc++/100577 #include <ranges> +#include <functional> namespace ranges = std::ranges; namespace views = std::ranges::views; @@ -113,4 +114,17 @@ test03() x | std::views::drop(S{}); } +void +test04() +{ + // Non-trivially-copyable extra arguments make a closure not simple. + using F = std::function<bool(bool)>; + static_assert(!std::is_trivially_copyable_v<F>); + using views::__adaptor::__closure_has_simple_call_op; + static_assert(!__closure_has_simple_call_op<decltype(views::take_while(std::declval<F>()))>); + static_assert(!__closure_has_simple_call_op<decltype(views::drop_while(std::declval<F>()))>); + static_assert(!__closure_has_simple_call_op<decltype(views::filter(std::declval<F>()))>); + static_assert(!__closure_has_simple_call_op<decltype(views::transform(std::declval<F>()))>); +} + // { dg-prune-output "in requirements" } |