Re: [boost] Smart mutex pointer?

From: Mark Deric (laguna_at_[hidden])
Date: 2005-02-14 16:58:26

"Peter Dimov" <pdimov_at_[hidden]> wrote:

> > struct Dummy { int a; }
> >
> > class Lock {
> > private:
> >  Dummy &_d;
> > public:
> >  Lock( Dummy &d ) : _d(d) { std::cout << "Locked." << std::endl; }
> >  ~Lock( void ) { std::cout << "Unlocked." << std::endl; }
> >
> >  Dummy *operator->( void ) { return &_d; }
> > };
> >
> > class Ref {
> > private:
> >  Dummy &_d;
> > public:
> >  Ref( Dummy &d ) : _d(d) { }
> >
> >   Lock operator->(void) { return Lock(_d); }
> > };

> Your code is non-portable. You are assuming that the temporary
> Lock(_d) will be constructed directly in the return value, but this is
> not guaranteed.

I'm not sure I'm following "constructed directly in the return value";
but, it will be constructed before the call to Lock's Dummy *operator->(
void ) as implied by x->a, below.  Isn't this all that is required?  
> int main( void )
> {
>    Dummy d;
>    Ref x(d);
> 
>    x->a = 1;
>    std::cout << x->a << std::endl;
> }