[Patch, libstdc++/64584, libstdc++/64585] Clear basic_regex after imbue and make assign exception tolerant

[Jonathan Wakely]

On 17/01/15 16:06 -0800, Tim Shen wrote:
>On Fri, Jan 16, 2015 at 4:12 AM, Jonathan Wakely <jwakely@redhat.com> wrote:
>> In that case, why bother using a unique_ptr initially, if it will just
>> have to allocate a shared_ptr control block later anyway? It's better
>> to use make_shared to reduce the number of allocations, isn't it?
>
>Yes you are right, I didn't notice that shared_ptr<_NFA> can be
>implicitly converted to shared_ptr<const _NFA>.
>
>Fixed.

OK for trunk and 4.9 - thanks.