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[rocThrust] Add fallback to std::decay_t when building against old libstdc++ #200

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Merged
umfranzw merged 1 commit into from
Jun 12, 2025
Merged

[rocThrust] Add fallback to std::decay_t when building against old libstdc++ #200

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12 changes: 11 additions & 1 deletion projects/rocthrust/thrust/detail/functional/actor.h
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
/*
* Copyright 2024 NVIDIA Corporation
* Modifications Copyright© 2025 Advanced Micro Devices, Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
Expand Down Expand Up @@ -40,6 +41,15 @@ namespace detail
namespace functional
{

// If we have libstdc++ >= 10, we can use the __decay_t
// builtin to reduce compilation time.
template<typename T>
#if defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE < 10
using decay_t = std::decay_t<T>;
#else
using decay_t = std::__decay_t<T>;
#endif
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@marbre marbre Jun 20, 2025

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As mentioned on PR #224, this change breaks compiling rocThrust on Windows with MSVC:

[rocThrust] C:/home/runner/_work/TheRock/TheRock/math-libs/rocThrust/thrust/..\thrust/detail/functional/actor.h:50:22: error: no template named '__decay_t' in namespace 'std'; did you mean 'decay_t'?
[rocThrust]    50 | using decay_t = std::__decay_t<T>;
[rocThrust]       |                 ~~~~~^~~~~~~~~
[rocThrust]       |                      decay_t
[rocThrust] C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.44.35207\include\type_traits:1267:1: note: 'decay_t' declared here

[rocThrust]  1267 | using decay_t = typename decay<_Ty>::type;

[rocThrust]       | ^

[rocThrust] 1 error generated when compiling for gfx1100.

(from https://github.com/ROCm/TheRock/actions/runs/15784597552/job/44498186375?pr=882#step:12:725)


// An actor is a node in an expression template
template <typename Eval>
struct actor : Eval
Expand Down Expand Up @@ -197,7 +207,7 @@ struct value
};

template <typename T>
THRUST_HOST_DEVICE auto make_actor(T&& x) -> actor<value<std::__decay_t<T>>>
THRUST_HOST_DEVICE auto make_actor(T&& x) -> actor<value<thrust::detail::functional::decay_t<T>>>
{
return {{THRUST_FWD(x)}};
}
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