On Fri, 19 Dec 2025, 12:26 Tomasz Kamiński, <[email protected]> wrote:
> This functions are indirectly called from flat_ containers operations
> (from preconditions check of lower_bound, upper_bound, ...) that were
> made constexpr by r16-6026-gbf9dd44a97400e, leading to test with
> in _GLIBCXX_DEBUG mode.
>
> For __can_advance we uncoditionally return true in constant evaluation,
> similary to __valid_range. The constexpr iterator will detect comparision
> of iterator to different ranges.
>
Thanks for fixing this! Our test results should be clean now.
> libstdc++-v3/ChangeLog:
>
> * include/debug/helper_functions.h (__gnu_debug::__can_advance):
> Declare as _GLIBCXX20_CONSTEXPR.
> * include/debug/safe_iterator.h (__gnu_debug::__can_advance):
> Define as _GLIBCXX20_CONSTEXPR, and return true for constexpr
> evaluation.
> (__gnu_debug::__base): Define as _GLIBCXX20_CONSTEXPR.
> ---
> Tested on x86_64-linux. Pushed to trunk.
>
> libstdc++-v3/include/debug/helper_functions.h | 4 ++--
> libstdc++-v3/include/debug/safe_iterator.h | 18 +++++++++++++++---
> 2 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/libstdc++-v3/include/debug/helper_functions.h
> b/libstdc++-v3/include/debug/helper_functions.h
> index b9771034bf3..b058408a1e3 100644
> --- a/libstdc++-v3/include/debug/helper_functions.h
> +++ b/libstdc++-v3/include/debug/helper_functions.h
> @@ -292,7 +292,7 @@ namespace __gnu_debug
>
> template<typename _Iterator, typename _Sequence, typename _Category,
> typename _Size>
> - bool
> + _GLIBCXX20_CONSTEXPR bool
> __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
> _Size);
>
> @@ -304,7 +304,7 @@ namespace __gnu_debug
>
> template<typename _Iterator, typename _Sequence, typename _Category,
> typename _Diff>
> - bool
> + _GLIBCXX20_CONSTEXPR bool
> __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
> const std::pair<_Diff, _Distance_precision>&, int);
>
> diff --git a/libstdc++-v3/include/debug/safe_iterator.h
> b/libstdc++-v3/include/debug/safe_iterator.h
> index 80ed9570ecb..ef61ab5e026 100644
> --- a/libstdc++-v3/include/debug/safe_iterator.h
> +++ b/libstdc++-v3/include/debug/safe_iterator.h
> @@ -1145,21 +1145,33 @@ namespace __gnu_debug
>
> template<typename _Iterator, typename _Sequence, typename _Category,
> typename _Size>
> + _GLIBCXX20_CONSTEXPR
> inline bool
> __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&
> __it,
> _Size __n)
> - { return __it._M_can_advance(__n); }
> + {
> + if (std::__is_constant_evaluated())
> + return true;
> +
> + return __it._M_can_advance(__n);
> + }
>
> template<typename _Iterator, typename _Sequence, typename _Category,
> typename _Diff>
> + _GLIBCXX20_CONSTEXPR
> inline bool
> __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&
> __it,
> const std::pair<_Diff, _Distance_precision>& __dist,
> int __way)
> - { return __it._M_can_advance(__dist, __way); }
> + {
> + if (std::__is_constant_evaluated())
> + return true;
> +
> + return __it._M_can_advance(__dist, __way);
> + }
>
> template<typename _Iterator, typename _Sequence>
> - _Iterator
> + _GLIBCXX20_CONSTEXPR _Iterator
> __base(const _Safe_iterator<_Iterator, _Sequence,
> std::random_access_iterator_tag>& __it)
> { return __it.base(); }
> --
> 2.52.0
>
>
