id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
11032,boost::offset_ptr needs explicit ctor,stheophil@…,Ion Gaztañaga,"Both the libc++ std library implementation and the MSVC library implementation require that their pointer types can be upcast. 

The list and tree data structures have a class hierarchy of node types and often seem to pass pointers to the base types (or to offset_ptr<void>) that are then upcast to the most derived types. offset_ptr has no explicit constructor that allows upcasts, only implicit ctors for downcasts. 

We have patched our version of offset_ptr with this constructor:

{{{
//!Explicit constructor from other offset_ptr. Never throws.
template<class T2>
explicit offset_ptr(const offset_ptr<T2, DifferenceType, OffsetType, OffsetAlignment> &ptr
   , typename ipcdetail::enable_if_c<
   !ipcdetail::is_convertible<T2*, PointedType*>::value 
    >::type * = 0)
    : internal(ipcdetail::offset_ptr_to_offset<OffsetType>(static_cast<PointedType*>(ptr.get()), this))
 {}

}}}
 
",Bugs,new,To Be Determined,interprocess,Boost 1.57.0,Problem,,,