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Fix uninitialized read in uninitialized_copy_n #5811

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Merged
bernhardmgruber merged 1 commit into from
Sep 9, 2025
+7 −4
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Fix uninitialized read in uninitialized_copy_n #5811

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11 changes: 7 additions & 4 deletions thrust/thrust/system/cuda/detail/uninitialized_copy.h
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Original file line number Diff line number Diff line change
Expand Up @@ -86,10 +86,13 @@ OutputIt _CCCL_HOST_DEVICE
uninitialized_copy_n(execution_policy<Derived>& policy, InputIt first, Size count, OutputIt result)
{
// if the output type is trivially constructible from the input, it has no side effect, and we can skip placement new
// and calling a constructor. So we can delegate to copy_n.
using ctor_arg_t = thrust::detail::raw_reference_t<::cuda::std::iter_reference_t<InputIt>>;
using output_t = thrust::detail::it_value_t<OutputIt>;
if constexpr (::cuda::std::is_trivially_constructible_v<output_t, ctor_arg_t>)
// and calling a constructor. Furthermore, if assigning an input to an output element is also trivial, there is no
// copy constructor which could have a side effect and we can delegate to copy_n.
using input_ref_t = thrust::detail::raw_reference_t<::cuda::std::iter_reference_t<InputIt>>;
using output_ref_t = thrust::detail::raw_reference_t<::cuda::std::iter_reference_t<OutputIt>>;
using output_t = thrust::detail::it_value_t<OutputIt>;
if constexpr (::cuda::std::is_trivially_constructible_v<output_t, input_ref_t>
&& ::cuda::std::is_trivially_assignable_v<output_ref_t, input_ref_t>)
{
cuda_cub::copy_n(policy, first, count, result);
}
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