On Fri, Sep 18, 2026 at 5:02 PM Jonathan Wakely <[email protected]> wrote:
> On Fri, 18 Sept 2026 at 15:50, Tomasz Kamiński <[email protected]> > wrote: > > > > The checks against _M_current being negive were disabled for cases where > > _Bound denotes unreachable_sentinel_t. However, _M_current has ptrdiff_t > > type in that case, and this check are as meaningfull are for integer > bound. > > The standard seems to suggest that it's OK to pass a negative bound > for an unreachable sentinel. > > Preconditions: If Bound is not unreachable_sentinel_t, b ≥ 0. > If you mean this one: https://eel.is/c++draft/range.repeat#iterator-2 It's an exposition-only private constructor, and a negative bound is never passed to it as you would hit UB in constructors: https://eel.is/c++draft/range.repeat#view-1 > > This change would cause assertions for the code that isn't forbidden > by the standard. Or am I missing something? > > > > > > libstdc++-v3/ChangeLog: > > > > * include/std/ranges (repeat_view::_Iterator::_Iterator) > > (repeat_view::_Iterator::operator--) > > (repeat_view::_Iterator::operator+=) > > (repeat_view::_Iterator::operator-=): Unconditionally assert > > on _M_current having non-negative value. > > --- > > Noticed that when working on extracting _Repeat_iterator (that I > > templated with _IndexType). Worth to be separate. > > > > Testing on x86_64-linux. *repeat* view passed with all standard > > modes, debug and assertions. OK for trunk? > > > > libstdc++-v3/include/std/ranges | 14 ++++---------- > > 1 file changed, 4 insertions(+), 10 deletions(-) > > > > diff --git a/libstdc++-v3/include/std/ranges > b/libstdc++-v3/include/std/ranges > > index 1c0991cae13..a0ce157d4f2 100644 > > --- a/libstdc++-v3/include/std/ranges > > +++ b/libstdc++-v3/include/std/ranges > > @@ -8075,10 +8075,7 @@ namespace views::__adaptor > > constexpr explicit > > _Iterator(const _Tp* __value, __index_type __bound = __index_type()) > > : _M_value(__value), _M_current(__bound) > > - { > > - if constexpr (!same_as<_Bound, unreachable_sentinel_t>) > > - __glibcxx_assert(__bound >= 0); > > - } > > + { __glibcxx_assert(__bound >= 0); } > > > > friend repeat_view; > > > > @@ -8112,8 +8109,7 @@ namespace views::__adaptor > > constexpr _Iterator& > > operator--() > > { > > - if constexpr (!same_as<_Bound, unreachable_sentinel_t>) > > - __glibcxx_assert(_M_current > 0); > > + __glibcxx_assert(_M_current > 0); > > --_M_current; > > return *this; > > } > > @@ -8129,8 +8125,7 @@ namespace views::__adaptor > > constexpr _Iterator& > > operator+=(difference_type __n) > > { > > - if constexpr (!same_as<_Bound, unreachable_sentinel_t>) > > - __glibcxx_assert(_M_current + __n >= 0); > > + __glibcxx_assert(_M_current + __n >= 0); > > _M_current += __n; > > return *this; > > } > > @@ -8138,8 +8133,7 @@ namespace views::__adaptor > > constexpr _Iterator& > > operator-=(difference_type __n) > > { > > - if constexpr (!same_as<_Bound, unreachable_sentinel_t>) > > - __glibcxx_assert(_M_current - __n >= 0); > > + __glibcxx_assert(_M_current - __n >= 0); > > _M_current -= __n; > > return *this; > > } > > -- > > 2.55.0 > > > >
