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[libc++] Add missing assertion in std::span constructor #118396

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Merged
merged 3 commits into from
Dec 9, 2024
Merged

[libc++] Add missing assertion in std::span constructor #118396

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2f686b7
[libc++] Add missing assertion in std::span constructor
ldionne Dec 2, 2024
8416929
Fix assertion condition per review comment
ldionne Dec 6, 2024
5b32654
Reword comments in test file
ldionne Dec 6, 2024
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7 changes: 6 additions & 1 deletion libcxx/include/span
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Original file line number Diff line number Diff line change
Expand Up @@ -267,6 +267,8 @@ public:
_LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} {
(void)__count;
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)");
_LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr,
"passed nullptr with non-zero length in span's constructor (iterator, len)");
}

template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
Expand Down Expand Up @@ -441,7 +443,10 @@ public:

template <__span_compatible_iterator<element_type> _It>
_LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count)
: __data_{std::to_address(__first)}, __size_{__count} {}
: __data_{std::to_address(__first)}, __size_{__count} {
_LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr,
"passed nullptr with non-zero length in span's constructor (iterator, len)");
}

template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
_LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last)
Expand Down
47 changes: 41 additions & 6 deletions libcxx/test/libcxx/containers/views/views.span/span.cons/assert.iter_size.pass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,13 +25,48 @@
#include "check_assertion.h"

int main(int, char**) {
std::array<int, 3> array{0, 1, 2};
std::array<int, 3> array{0, 1, 2};

auto too_large = [&] { std::span<int, 3> const s(array.data(), 4); (void)s; };
TEST_LIBCPP_ASSERT_FAILURE(too_large(), "size mismatch in span's constructor (iterator, len)");
// Input range too large (exceeds the span extent)
{
auto f = [&] {
std::span<int, 3> const s(array.data(), 4);
(void)s;
};
TEST_LIBCPP_ASSERT_FAILURE(f(), "size mismatch in span's constructor (iterator, len)");
}

auto too_small = [&] { std::span<int, 3> const s(array.data(), 2); (void)s; };
TEST_LIBCPP_ASSERT_FAILURE(too_small(), "size mismatch in span's constructor (iterator, len)");
// Input range too small (doesn't fill the span)
{
auto f = [&] {
std::span<int, 3> const s(array.data(), 2);
(void)s;
};
TEST_LIBCPP_ASSERT_FAILURE(f(), "size mismatch in span's constructor (iterator, len)");
}

return 0;
// Input range is non-empty but starts with a null pointer
{
// static extent
{
auto f = [&] {
int* p = nullptr;
std::span<int, 3> const s(p, 3);
(void)s;
};
TEST_LIBCPP_ASSERT_FAILURE(f(), "passed nullptr with non-zero length in span's constructor (iterator, len)");
}

// dynamic extent
{
auto f = [&] {
int* p = nullptr;
std::span<int, std::dynamic_extent> const s(p, 1);
(void)s;
};
TEST_LIBCPP_ASSERT_FAILURE(f(), "passed nullptr with non-zero length in span's constructor (iterator, len)");
}
}

return 0;
}
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