https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108556
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Compiling with -D_GLIBCXX_DEBUG shows the problem:
/home/jwakely/gcc/13/include/c++/13.0.1/bits/stl_algo.h:4892:
In function:
void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter =
gnu_debug::_Safe_iterator<gnu_cxx::normal_iterator<Item*, vector<Item,
allocator<Item> > >, debug::vector<Item>, random_access_iterator_tag>;
_Compare = main()::<lambda(const Item&, const Item&)>]
Error: comparison doesn't meet irreflexive requirements, assert(!(a < a)).
Objects involved in the operation:
instance "functor" @ 0x7ffee875415f {
type = main::{lambda(Item const&, Item const&)#1};
}
iterator::value_type "ordered type" {
type = Item;
}
Aborted (core dumped)
Your comparison function fails to meet the requirements of a strict weak
ordering, so your program has undefined behaviour.
https://www.boost.org/sgi/stl/StrictWeakOrdering.html
https://en.cppreference.com/w/cpp/named_req/Compare
