Re: [boost] [bug] Error in optional's converting assignment operator

30 Dec 2005

      Joe Gottman wrote:
...
There is an error in the implementation of the converting assignment
operator for optional<T>. It is currently implemented as
template<class U>
optional& operator= ( optional<U> const& rhs )
{
   this->assign(rhs.get());
   return *this ;
}
The problem with this is that if rhs is not initialized then rhs.get()
asserts. This function should be rewritten as
template<class U>
optional& operator= ( optional<U> const& rhs )
{
   if (rhs.is_initialized())
       this->assign(rhs.get());
   else
       destroy();
   return *this ;
}
Yikes!
Of course...
The fix is not as simple as that (because destroy() invokes UB if '*this' is 
absent), but, ya, that's the idea.

Thank for reporting it!

Fernando Cacciola
SciSoft