diff options
Diffstat (limited to 'src/span.h')
| -rw-r--r-- | src/span.h | 37 |
1 files changed, 33 insertions, 4 deletions
diff --git a/src/span.h b/src/span.h index 4afb383a59..830164514b 100644 --- a/src/span.h +++ b/src/span.h @@ -18,6 +18,16 @@ #define ASSERT_IF_DEBUG(x) #endif +#if defined(__clang__) +#if __has_attribute(lifetimebound) +#define SPAN_ATTR_LIFETIMEBOUND [[clang::lifetimebound]] +#else +#define SPAN_ATTR_LIFETIMEBOUND +#endif +#else +#define SPAN_ATTR_LIFETIMEBOUND +#endif + /** A Span is an object that can refer to a contiguous sequence of objects. * * It implements a subset of C++20's std::span. @@ -84,6 +94,14 @@ class Span C* m_data; std::size_t m_size; + template <class T> + struct is_Span_int : public std::false_type {}; + template <class T> + struct is_Span_int<Span<T>> : public std::true_type {}; + template <class T> + struct is_Span : public is_Span_int<typename std::remove_cv<T>::type>{}; + + public: constexpr Span() noexcept : m_data(nullptr), m_size(0) {} @@ -134,8 +152,19 @@ public: * To prevent surprises, only Spans for constant value types are supported when passing in temporaries. * Note that this restriction does not exist when converting arrays or other Spans (see above). */ - template <typename V, typename std::enable_if<(std::is_const<C>::value || std::is_lvalue_reference<V>::value) && std::is_convertible<typename std::remove_pointer<decltype(std::declval<V&>().data())>::type (*)[], C (*)[]>::value && std::is_convertible<decltype(std::declval<V&>().size()), std::size_t>::value, int>::type = 0> - constexpr Span(V&& v) noexcept : m_data(v.data()), m_size(v.size()) {} + template <typename V> + constexpr Span(V& other SPAN_ATTR_LIFETIMEBOUND, + typename std::enable_if<!is_Span<V>::value && + std::is_convertible<typename std::remove_pointer<decltype(std::declval<V&>().data())>::type (*)[], C (*)[]>::value && + std::is_convertible<decltype(std::declval<V&>().size()), std::size_t>::value, std::nullptr_t>::type = nullptr) + : m_data(other.data()), m_size(other.size()){} + + template <typename V> + constexpr Span(const V& other SPAN_ATTR_LIFETIMEBOUND, + typename std::enable_if<!is_Span<V>::value && + std::is_convertible<typename std::remove_pointer<decltype(std::declval<const V&>().data())>::type (*)[], C (*)[]>::value && + std::is_convertible<decltype(std::declval<const V&>().size()), std::size_t>::value, std::nullptr_t>::type = nullptr) + : m_data(other.data()), m_size(other.size()){} constexpr C* data() const noexcept { return m_data; } constexpr C* begin() const noexcept { return m_data; } @@ -192,9 +221,9 @@ public: /** MakeSpan for arrays: */ template <typename A, int N> Span<A> constexpr MakeSpan(A (&a)[N]) { return Span<A>(a, N); } /** MakeSpan for temporaries / rvalue references, only supporting const output. */ -template <typename V> constexpr auto MakeSpan(V&& v) -> typename std::enable_if<!std::is_lvalue_reference<V>::value, Span<const typename std::remove_pointer<decltype(v.data())>::type>>::type { return std::forward<V>(v); } +template <typename V> constexpr auto MakeSpan(V&& v SPAN_ATTR_LIFETIMEBOUND) -> typename std::enable_if<!std::is_lvalue_reference<V>::value, Span<const typename std::remove_pointer<decltype(v.data())>::type>>::type { return std::forward<V>(v); } /** MakeSpan for (lvalue) references, supporting mutable output. */ -template <typename V> constexpr auto MakeSpan(V& v) -> Span<typename std::remove_pointer<decltype(v.data())>::type> { return v; } +template <typename V> constexpr auto MakeSpan(V& v SPAN_ATTR_LIFETIMEBOUND) -> Span<typename std::remove_pointer<decltype(v.data())>::type> { return v; } /** Pop the last element off a span, and return a reference to that element. */ template <typename T> |