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

From: Fernando Cacciola (fernando_cacciola_at_[hidden])
Date: 2005-12-30 10:20:10

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