Committed with the advised changes.

Ok, I'll backport next week.

Thanks

On 19/10/2023 10:05, Jonathan Wakely wrote:
>
>
> On Thursday, 19 October 2023, François Dumont <frs.dumont@gmail.com> 
> wrote:
> > libstdc++: [_Hashtable] Do not reuse untrusted cached hash code
> >
> > On merge reuse merged node cached hash code only if we are on the 
> same type of
> > hash and this hash is stateless. Usage of function pointers or 
> std::function as
> > hash functor will prevent this optimization.
>
> I found this first sentence a little hard to parse. How about:
>
> On merge, reuse a merged node's cached hash code only if we are on the 
> same
> type of
> hash and this hash is stateless.
>
>
> And for the second sentence, would it be clearer to say "will prevent 
> reusing cached hash codes" instead of "will prevent this optimization"?
>
>
> And for the comment on the new function, I think this reads better:
>
> "Only use the node's (possibly cached) hash code if its hash function 
> _H2 matches _Hash. Otherwise recompute it using _Hash."
>
> The code and tests look good, so if you're happy with the 
> comment+changelog suggestions, this is ok for trunk.
>
> This seems like a bug fix that should be backported too, after some 
> time on trunk.
>
>
> >
> > libstdc++-v3/ChangeLog
> >
> >     * include/bits/hashtable_policy.h
> >     (_Hash_code_base::_M_hash_code(const _Hash&, const 
> _Hash_node_value<>&)): Remove.
> >     (_Hash_code_base::_M_hash_code<_H2>(const _H2&, const 
> _Hash_node_value<>&)): Remove.
> >     * include/bits/hashtable.h
> >     (_M_src_hash_code<_H2>(const _H2&, const key_type&, const 
> __node_value_type&)): New.
> >     (_M_merge_unique<>, _M_merge_multi<>): Use latter.
> >     * testsuite/23_containers/unordered_map/modifiers/merge.cc
> >     (test04, test05, test06): New test cases.
> >
> > Tested under Linux x86_64, ok to commit ?
> >
> > François
> >
> >