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Make pointer-based Span construction safer

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This prevents constructing a Span<A> given two pointers into an array
of B (where B is a subclass of A), at least without explicit cast to
pointers to A.
This commit is contained in:
Pieter Wuille 2020-03-29 16:58:04 -07:00
parent 1f790a1147
commit bb3d38fc06
1 changed files with 15 additions and 2 deletions
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17
src/span.h
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@ -22,9 +22,22 @@ class Span
public:
constexpr Span() noexcept : m_data(nullptr), m_size(0) {}
constexpr Span(C* data, std::size_t size) noexcept : m_data(data), m_size(size) {}
constexpr Span(C* data, C* end) noexcept : m_data(data), m_size(end - data) {}
/** Construct a span from a begin pointer and a size.
*
* This implements a subset of the iterator-based std::span constructor in C++20,
* which is hard to implement without std::address_of.
*/
template <typename T, typename std::enable_if<std::is_convertible<T (*)[], C (*)[]>::value, int>::type = 0>
constexpr Span(T* begin, std::size_t size) noexcept : m_data(begin), m_size(size) {}
/** Construct a span from a begin and end pointer.
*
* This implements a subset of the iterator-based std::span constructor in C++20,
* which is hard to implement without std::address_of.
*/
template <typename T, typename std::enable_if<std::is_convertible<T (*)[], C (*)[]>::value, int>::type = 0>
constexpr Span(T* begin, T* end) noexcept : m_data(begin), m_size(end - begin) {}
/** Implicit conversion of spans between compatible types.
*