https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122224
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2025-10-09
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
We could make the erroneous std::prev call a no-op though:
-- a/libstdc++-v3/include/bits/stl_iterator_base_funcs.h
+++ b/libstdc++-v3/include/bits/stl_iterator_base_funcs.h
@@ -201,7 +201,7 @@ namespace __detail
// concept requirements
__glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
__glibcxx_assert(__n >= 0);
- while (__n--)
+ while (__n-- > 0)
++__i;
}
I was going to do that only if n was an integral type, because otherwise we
don't know if the > operator works or not (which
https://cplusplus.github.io/LWG/issue3439 needs to fix) but we already do __n
>= 0 for the assertion.
So let's make this change. If the assertion is not enabled then it's better to
do nothing than to have undefined behaviour.
