Unexpected greedy ops failure

[François Dumont]

With the patch proposed in: 
https://gcc.gnu.org/pipermail/libstdc++/2021-August/053009.html to 
extend some _GLIBCXX_DEBUG checks in _GLIBCXX_ASSERTIONS I have 2 tests 
in failure:

Running target unix/-D_GLIBCXX_DEBUG
Running 
/home/fdt/dev/gcc/git/libstdc++-v3/testsuite/libstdc++-dg/conformance.exp 
...
FAIL: 23_containers/deque/types/1.cc (test for excess errors)
FAIL: 23_containers/vector/types/1.cc (test for excess errors)

The error is:

/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/debug/helper_functions.h:96: 
error: ambiguous overload for 'operator-' in '__rhs - __lhs' (operand 
types are 'std::move_iterator<greedy_ops::X*>' and 
'std::move_iterator<greedy_ops::X*>')
In file included from 
/home/fdt/dev/gcc/git/libstdc++-v3/testsuite/23_containers/vector/types/1.cc:24:
/home/fdt/dev/gcc/git/libstdc++-v3/testsuite/util/testsuite_greedy_ops.h:48: 
note: candidate: 'greedy_ops::X greedy_ops::operator-(T, T) [with T = 
std::move_iterator<greedy_ops::X*>]'
In file included from 
/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/stl_algobase.h:67,
                  from 
/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/vector:60,
                  from 
/home/fdt/dev/gcc/git/libstdc++-v3/testsuite/23_containers/vector/types/1.cc:23:
/home/fdt/dev/gcc/build/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/stl_iterator.h:1692: 
note: candidate: 'constexpr decltype ((__x.base() - __y.base())) 
std::operator-(const std::move_iterator<_IteratorL>&, const 
std::move_iterator<_IteratorR>&) [with _IteratorL = gree
dy_ops::X*; _IteratorR = greedy_ops::X*; decltype ((__x.base() - 
__y.base())) = long int]'
compiler exited with status 1
FAIL: 23_containers/vector/types/1.cc (test for excess errors)

I really don"t understand the link between the failures and this patch.

But at the same time I am surprised that there is no definition for 
operator-(const move_iterator&, const move_iterator&) in the library 
(like in attached patch). With this change the failure vanishes.

Moreover is there a reason for having added several operators as normal 
std namespace operators rather than inline friend like in my patch ? I 
know we already talk about it but I don't remember if the reply was that 
we cannot do it or I simply forgot to propose the patch to do so.

Thanks,

François

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