Re: std::regex: inserting std::wregex to std::vector loses some std::wregex values

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi,

On 09/15/2014 06:46 PM, Tim Shen wrote:
> On Mon, Sep 15, 2014 at 3:10 AM, Jonathan Wakely <jwakely@redhat.com> wrote:
> > With this patch basic_regex::_M_traits becames a pointer, but that
> > pointer becomes null after a move - is that safe?
> >
> > It looks wrong to allocate a traits object in the default constructor
> > but not in the move constructor, and to allow _M_traits to be null
> > following assign(), e.g. does this work OK after your patch?
> >
> >   std::regex r;
> >   std::regex rr = std::move(r);
> >   r.assign("a");
> >   regex_match("a", r);
> No it doesn't, sorry. The reason _M_traits can't be nullptr is imbue()
> and getloc(), so should we implement move constructor using default
> construction and swap?
But then the move constructor can't be noexcept anymore, because I see 
that currently the default constructor isn't noexcept. Thus we should 
first make sure that the default constructor is noexcept, which is a 
good idea anyway.

Paolo.