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4ff71c91d3
backport std::ssize to c10 Summary: Now that we have -Werror=sign-compare enabled, we encounter a lot of friction comparing standard containers and our tensors which are signed. std::ssize will make it easier and safer to succinctly convert container sizes to a signed type. Test Plan: Added a unit test. Reviewers: ezyang Subscribers: Tasks: Tags: --- Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/pytorch/pytorch/pull/97442). * #97443 * __->__ #97442 Pull Request resolved: https://github.com/pytorch/pytorch/pull/97442 Approved by: https://github.com/ezyang
46 lines
1.3 KiB
C++
46 lines
1.3 KiB
C++
#pragma once
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#include <c10/util/Exception.h>
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#include <c10/util/TypeSafeSignMath.h>
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#include <cstddef>
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#include <type_traits>
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namespace c10 {
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// Implementations of std::ssize() from C++ 20.
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//
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// This is useful in particular for avoiding -Werror=sign-compare
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// issues.
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//
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// Use this with argument-dependent lookup, e.g.:
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// use c10::ssize;
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// auto size = ssize(container);
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//
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// As with the standard library version, containers are permitted to
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// specialize this with a free function defined in the same namespace.
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//
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// See https://en.cppreference.com/w/cpp/iterator/size for more
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// information as well as the source of our implementations.
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//
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// We augment the implementation by adding an assert() if an overflow
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// would occur.
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template <typename C>
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constexpr auto ssize(const C& c) -> std::
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common_type_t<std::ptrdiff_t, std::make_signed_t<decltype(c.size())>> {
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using R = std::
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common_type_t<std::ptrdiff_t, std::make_signed_t<decltype(c.size())>>;
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// We expect this to be exceedingly rare to fire and don't wish to
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// pay a performance hit in release mode.
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TORCH_INTERNAL_ASSERT_DEBUG_ONLY(!greater_than_max<R>(c.size()));
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return static_cast<R>(c.size());
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}
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template <typename T, std::ptrdiff_t N>
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constexpr auto ssize(const T (&array)[N]) noexcept -> std::ptrdiff_t {
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return N;
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}
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} // namespace c10
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