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| author | Neil MacIntosh <neilmac@fb.com> | 2018-03-03 19:12:45 -0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2018-03-03 19:12:45 -0800 |
| commit | 6a33b97a84f9c0a60ede78b5db98647e9a48d6c9 (patch) | |
| tree | 843904bdf2e4a60554a30960df4557a8ef815746 /include | |
| parent | cbd64c9ff6c45cdbf0312a1829d1f76f713403dd (diff) | |
| download | platform_external_Microsoft-GSL-6a33b97a84f9c0a60ede78b5db98647e9a48d6c9.tar.gz platform_external_Microsoft-GSL-6a33b97a84f9c0a60ede78b5db98647e9a48d6c9.tar.bz2 platform_external_Microsoft-GSL-6a33b97a84f9c0a60ede78b5db98647e9a48d6c9.zip | |
Fix return type of templated span.subspan() (#625)
* Added support for returning fixed-spize spans from subspan().
* Addressed issues from code review.
* Took simpler approach to static data member.
* Subtle fix to support MSVC 15.
* Helps to not introduce extraneous >
Diffstat (limited to 'include')
| -rw-r--r-- | include/gsl/span | 28 |
1 files changed, 26 insertions, 2 deletions
diff --git a/include/gsl/span b/include/gsl/span index e8ccb35..22e8459 100644 --- a/include/gsl/span +++ b/include/gsl/span @@ -45,8 +45,17 @@ #if _MSC_VER < 1910 #pragma push_macro("constexpr") #define constexpr /*constexpr*/ +#define GSL_USE_STATIC_CONSTEXPR_WORKAROUND #endif // _MSC_VER < 1910 +#else // _MSC_VER + +// See if we have enough C++17 power to use a static constexpr data member +// without needing an out-of-line definition +#if !(defined(__cplusplus) && (__cplusplus >= 201703L)) +#define GSL_USE_STATIC_CONSTEXPR_WORKAROUND +#endif // !(defined(__cplusplus) && (__cplusplus >= 201703L)) + #endif // _MSC_VER #define GSL_NOEXCEPT noexcept @@ -302,6 +311,12 @@ namespace details private: index_type size_; }; + + template <class ElementType, std::ptrdiff_t Extent, std::ptrdiff_t Offset, std::ptrdiff_t Count> + struct calculate_subspan_type + { + using type = span<ElementType, Count != dynamic_extent ? Count : (Extent != dynamic_extent ? Extent - Offset : Extent)>; + }; } // namespace details // [span], class template span @@ -323,7 +338,11 @@ public: using size_type = index_type; - constexpr static const index_type extent = Extent; +#if defined(GSL_USE_STATIC_CONSTEXPR_WORKAROUND) + static constexpr const index_type extent { Extent }; +#else + static constexpr index_type extent { Extent }; +#endif // [span.cons], span constructors, copy, assignment, and destructor template <bool Dependent = false, @@ -412,7 +431,7 @@ public: } template <std::ptrdiff_t Offset, std::ptrdiff_t Count = dynamic_extent> - constexpr span<element_type, Count> subspan() const + constexpr auto subspan() const -> typename details::calculate_subspan_type<ElementType, Extent, Offset, Count>::type { Expects((Offset >= 0 && size() - Offset >= 0) && (Count == dynamic_extent || (Count >= 0 && Offset + Count <= size()))); @@ -525,6 +544,11 @@ private: } }; +#if defined(GSL_USE_STATIC_CONSTEXPR_WORKAROUND) +template <class ElementType, std::ptrdiff_t Extent> +constexpr const typename span<ElementType, Extent>::index_type span<ElementType, Extent>::extent; +#endif + // [span.comparison], span comparison operators template <class ElementType, std::ptrdiff_t FirstExtent, std::ptrdiff_t SecondExtent> |