[PATCH][_GLIBCXX_DEBUG] Limit performance impact in __erase_nodes_if

Jonathan Wakely jwakely@redhat.com
Fri Nov 19 10:43:24 GMT 2021


On Thu, 18 Nov 2021 at 22:05, François Dumont via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> Hi
>
>      Here is a proposal to limit performance impact of _GLIBCXX_DEBUG
> mode on __erase_nodes_if.
>
>      As you can see I am adding erase overloads on the Debug container
> to accept base iterators. So it exposes an additional non-Standard
> method, do you think it is any issue.
>

I think this is fine - I can't think of a way that this could make user
code do the wrong thing.


>
>      Note that I've started doing something similar for the vector/deque
> adding this time erase(_Base_const_iterator, _Base_const_iterator)
> overloads. But in this case it results in ambiguous erase calls, even if
> I remove the _Safe_iterator cast operator to the base iterator.
>
>      libstdc++: [_GLIBCXX_DEBUG] Reduce performance impact on std::erase_if
>
>      Bypass the _GLIBCXX_DEBUG additional checks in
> std::__detail::__erase_node_if used
>      by all implementations of std::erase_if for node based containers.
>
>      libstdc++-v3/ChangeLog:
>
>              * include/bits/erase_if.h (__erase_nodes_if): Add
> _UnsafeContainer template
>              parameter. Use it to get iterators to work with.
>              * include/debug/macros.h (__glibcxx_check_erase2): New.
>              * include/debug/map.h (map<>::erase(_Base_const_iterator)):
> New.
>              (map<>::erase(const_iterator)): Use latter.
>              * include/debug/multimap.h
> (multimap<>::erase(_Base_const_iterator)): New.
>              (multimap<>::erase(const_iterator)): Use latter.
>              * include/debug/multiset.h
> (multiset<>::erase(_Base_const_iterator)): New.
>              (multiset<>::erase(const_iterator)): Use latter.
>              * include/debug/set.h (set<>::erase(_Base_const_iterator)):
> New.
>              (set<>::erase(const_iterator)): Use latter.
>              * include/debug/unordered_map
> (unordered_map<>::erase(_Base_const_iterator)): New.
>              (unordered_multimap<>::erase(const_iterator)): New.
>              * include/debug/unordered_set
> (unordered_set<>::erase(_Base_const_iterator)): New.
>              (unordered_multiset<>::erase(const_iterator)): New.
>              * include/experimental/map (erase_if): Adapt.
>              * include/experimental/set (erase_if): Adapt.
>              * include/experimental/unordered_map (erase_if): Adapt.
>              * include/experimental/unordered_set (erase_if): Adapt.
>              * include/std/map (erase_if): Adapt.
>              * include/std/set (erase_if): Adapt.
>              * include/std/unordered_map (erase_if): Adapt.
>              * include/std/unordered_set (erase_if): Adapt.
>
> Tested under Linux x86_64,
>
> Ok to commit ?
>

OK, thanks.


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