This was inspired by LWG 4245 but goes further. Anything which only
reads or writes the _M_length member can be noexcept. That
member is an iterator difference_type which means it's a signed integer
type or the __max_diff_type integer-like class type, so all arithmetic
and comparisons are non-throwing.
libstdc++-v3/ChangeLog:
* include/bits/stl_iterator.h (counted_iterator): Add noexcept
to friend operators which only access the _M_length member.
---
Tested x86_64-linux.
libstdc++-v3/include/bits/stl_iterator.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/libstdc++-v3/include/bits/stl_iterator.h
b/libstdc++-v3/include/bits/stl_iterator.h
index bed72955d0c..478a98fe8a4 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -2511,17 +2511,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
[[nodiscard]]
friend constexpr iter_difference_t<_It2>
operator-(const counted_iterator& __x,
- const counted_iterator<_It2>& __y)
+ const counted_iterator<_It2>& __y) noexcept
{ return __y._M_length - __x._M_length; }
[[nodiscard]]
friend constexpr iter_difference_t<_It>
- operator-(const counted_iterator& __x, default_sentinel_t)
+ operator-(const counted_iterator& __x, default_sentinel_t) noexcept
{ return -__x._M_length; }
[[nodiscard]]
friend constexpr iter_difference_t<_It>
- operator-(default_sentinel_t, const counted_iterator& __y)
+ operator-(default_sentinel_t, const counted_iterator& __y) noexcept
{ return __y._M_length; }
constexpr counted_iterator&
@@ -2548,19 +2548,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
[[nodiscard]]
friend constexpr bool
operator==(const counted_iterator& __x,
- const counted_iterator<_It2>& __y)
+ const counted_iterator<_It2>& __y) noexcept
{ return __x._M_length == __y._M_length; }
[[nodiscard]]
friend constexpr bool
- operator==(const counted_iterator& __x, default_sentinel_t)
+ operator==(const counted_iterator& __x, default_sentinel_t) noexcept
{ return __x._M_length == 0; }
template<common_with<_It> _It2>
[[nodiscard]]
friend constexpr strong_ordering
operator<=>(const counted_iterator& __x,
- const counted_iterator<_It2>& __y)
+ const counted_iterator<_It2>& __y) noexcept
{ return __y._M_length <=> __x._M_length; }
[[nodiscard]]
--
2.49.0
