std::allocator should use sized delete

[Victor via libstdc++]

On Fri, 7 Jun 2019 10:17:33 +0100
  Jonathan Wakely <jwakely@redhat.com> wrote:
> No, because if you don't use the very latest version of 
>tcmalloc
> (released only two months ago) then sized delete can 
>crash the
> process.
> 
> See 
>https://gcc.gnu.org/ml/libstdc++/2019-05/msg00172.html 
>and the
> earlier mails on this list such as
> https://gcc.gnu.org/ml/libstdc++/2019-04/msg00012.html 
>and
> https://gcc.gnu.org/ml/libstdc++/2019-03/msg00020.html

How is tcmalloc version connected with gcc version? Is it 
ok to use gcc-10 with old tcmalloc?

I use gcc-9 on RHEL 7. Does it use tcmalloc or jemalloc by 
default?

Is there only problem with zero-size deallocation case?