[gcc r17-2305] libstdc++: Validate bound consistently in repeat_view constructors.

[Tomasz Kaminski]

https://gcc.gnu.org/g:c8c1f777617df6f1816900b779f32c80e016d7bd

commit r17-2305-gc8c1f777617df6f1816900b779f32c80e016d7bd
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date:   Fri Jul 10 08:43:02 2026 +0200

    libstdc++: Validate bound consistently in repeat_view constructors.
    
    Add checks for bound being non-negative to _Tp&& __value and
    piecewise_construct_t constructor. The later resolves LWG3772,
    "repeat_view's piecewise constructor is missing Postconditions".
    
    We use __detail::__is_signed_integer_like<_Bound> as the condition
    for performing the check, to avoid checking it for unsigned integers
    for which it is trivially met. As _Bound is constrained to either
    unreachable_sentinel_t or integer-like, this gives equivalent behavior
    to standard specified !same_as<_Bound, unreachable_sentinel_t>.
    
    libstdc++-v3/ChangeLog:
    
            * include/std/ranges (repeat_view::repeat_view): Assert that
            __bound >= 0 consistently. Replace !same_as<unreachable_sentinel>
            with __is_signed_integer_like check.
    
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
    Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>

Diff:
---
 libstdc++-v3/include/std/ranges | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 39a50b03e457..3e0df8d083c0 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -7918,14 +7918,17 @@ namespace views::__adaptor
     requires copy_constructible<_Tp>
     : _M_value(__value), _M_bound(__bound)
     {
-      if constexpr (!same_as<_Bound, unreachable_sentinel_t>)
+      if constexpr (__detail::__is_signed_integer_like<_Bound>)
 	__glibcxx_assert(__bound >= 0);
     }
 
     constexpr explicit
     repeat_view(_Tp&& __value, _Bound __bound = _Bound())
     : _M_value(std::move(__value)), _M_bound(__bound)
-    { }
+    {
+      if constexpr (__detail::__is_signed_integer_like<_Bound>)
+	__glibcxx_assert(__bound >= 0);
+    }
 
     template<typename... _Args, typename... _BoundArgs>
       requires constructible_from<_Tp, _Args...>
@@ -7936,7 +7939,10 @@ namespace views::__adaptor
 		tuple<_BoundArgs...> __bound_args = tuple<>{})
     : _M_value(std::make_from_tuple<_Tp>(std::move(__args))),
       _M_bound(std::make_from_tuple<_Bound>(std::move(__bound_args)))
-    { }
+    {
+      if constexpr (__detail::__is_signed_integer_like<_Bound>)
+	__glibcxx_assert(_M_bound >= 0);
+    }
 
     constexpr _Iterator
     begin() const