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[libc++] span: Fix incorrect return type of span::subspan 

The extent of the returned span was always std::dynamic_extent, which
is incorrect.

Thanks to Michael Schellenberger Costa for the patch.

Differential Revision: https://reviews.llvm.org/D71997
This commit is contained in:
Louis Dionne 2020-02-11 11:57:35 +01:00
parent 5ba931a84a
commit 92a1f65f17
2 changed files with 15 additions and 3 deletions
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2
libcxx/include/span
View File

@ -444,7 +444,7 @@ public:
template <size_t _Offset, size_t _Count = dynamic_extent>
_LIBCPP_INLINE_VISIBILITY
constexpr span<_Tp, dynamic_extent> subspan() const noexcept
constexpr span<element_type, _Count> subspan() const noexcept
{
_LIBCPP_ASSERT(_Offset <= size(), "Offset out of range in span::subspan()");
_LIBCPP_ASSERT(_Count == dynamic_extent || _Offset + _Count <= size(), "Count out of range in span::subspan()");

16
libcxx/test/std/containers/views/span.sub/subspan.pass.cpp
View File

@ -37,7 +37,13 @@ constexpr bool testConstexprSpan(Span sp)
using S2 = decltype(s2);
ASSERT_SAME_TYPE(typename Span::value_type, typename S1::value_type);
ASSERT_SAME_TYPE(typename Span::value_type, typename S2::value_type);
static_assert(S1::extent == (Span::extent == std::dynamic_extent ? std::dynamic_extent : Count), "");
if constexpr (Count != std::dynamic_extent) {
static_assert(S1::extent == Count);
} else if constexpr (Span::extent != std::dynamic_extent) {
static_assert(S1::extent == Span::extent - Offset);
} else {
static_assert(S1::extent == std::dynamic_extent);
}
static_assert(S2::extent == std::dynamic_extent, "");
return
s1.data() == s2.data()
@ -76,7 +82,13 @@ void testRuntimeSpan(Span sp)
using S2 = decltype(s2);
ASSERT_SAME_TYPE(typename Span::value_type, typename S1::value_type);
ASSERT_SAME_TYPE(typename Span::value_type, typename S2::value_type);
static_assert(S1::extent == (Span::extent == std::dynamic_extent ? std::dynamic_extent : Count), "");
if constexpr (Count != std::dynamic_extent) {
static_assert(S1::extent == Count);
} else if constexpr (Span::extent != std::dynamic_extent) {
static_assert(S1::extent == Span::extent - Offset);
} else {
static_assert(S1::extent == std::dynamic_extent);
}
static_assert(S2::extent == std::dynamic_extent, "");
assert(s1.data() == s2.data());
assert(s1.size() == s2.size());