https://gcc.gnu.org/g:0bcb57a2294fbadfa8388bdc3a5be356ad3cf91c
commit r17-2194-g0bcb57a2294fbadfa8388bdc3a5be356ad3cf91c Author: Tomasz Kamiński <[email protected]> Date: Fri Jul 3 14:41:02 2026 +0200 libstdc++: Validate user-provided stride values for layout_stride. Converting the __strides values using __index_type_cast asserts that they are non-negative and each value is representable as index_type. libstdc++-v3/ChangeLog: * include/std/mdspan (layout_stride::mapping::mapping(const extent_type&, span<...>)): Convert strides using __index_type_cast, which bring asserts for negative and unrepresentable values. * testsuite/23_containers/mdspan/layouts/stride_neg.cc: New test. Reviewed-by: Jonathan Wakely <[email protected]> Signed-off-by: Tomasz Kamiński <[email protected]> Diff: --- libstdc++-v3/include/std/mdspan | 3 ++- .../23_containers/mdspan/layouts/stride_neg.cc | 31 ++++++++++++++++++++++ 2 files changed, 33 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan index f5556f35fa14..23304e71b9df 100644 --- a/libstdc++-v3/include/std/mdspan +++ b/libstdc++-v3/include/std/mdspan @@ -1891,7 +1891,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION : _M_extents(__exts) { for (size_t __i = 0; __i < extents_type::rank(); ++__i) - _M_strides[__i] = index_type(as_const(__strides[__i])); + _M_strides[__i] = + __mdspan::__index_type_cast<index_type>(as_const(__strides[__i])); } template<typename _OIndexType> diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/stride_neg.cc b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/stride_neg.cc new file mode 100644 index 000000000000..153560bc82ff --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/stride_neg.cc @@ -0,0 +1,31 @@ +// { dg-do compile { target c++23 } } +#include <mdspan> + +#include "../layout_traits.h" +#include <cstdint> + +constexpr size_t dyn = std::dynamic_extent; + +constexpr bool +test_stride_overflow() +{ + auto exts = std::extents<uint8_t, dyn, dyn>(1, 3); + auto n = size_t(1) << 9; + auto m = std::layout_stride::mapping(exts, std::array{n, 1zu}); // { dg-error "expansion of" } + (void) m; + return true; +} +static_assert(test_stride_overflow()); // { dg-error "expansion of" } + +constexpr bool +test_stride_negative() +{ + auto exts = std::extents<std::size_t, dyn, dyn>(1, 3); + auto m = std::layout_stride::mapping(exts, std::array{1, -4}); // { dg-error "expansion of" } + (void) m; + return true; +} +static_assert(test_stride_negative()); // { dg-error "expansion of" } + +// { dg-prune-output "non-constant condition for static assertion" } +// { dg-prune-output "__glibcxx_assert_fail()" }
