Re: [Boost-users] A question about shared_ptr

Zhuo Hao wrote:

In file , I find the following function: /begin quote template shared_ptr(Y * p, D d): px(p), pn(p, d) { detail::sp_enable_shared_from_this( pn, p, p ); } /end quote If I use it as follows:"boost::shared_ptr<Investment> pInv(0,getRidOfInvestment)",it will not compile.But when I use:"boost::shared_ptr<Investment> pInv(static_cast(0),getRidOfInvestment)",it can be compiled. The constructor's first parameter is Y*,i.e.,a pointer to Y.And 0 can be interpreted as a pointer to Y,too. Why can't zero be treated as a pointer to Y here?

Y (the type of the object passed as the first parameter of the constructor) may not be the same as T (the type of the shared pointer). In other words I can have shared_ptr<Investment> p(new SpecificInvestment(), getRidOfInvestment); as long as class SpecificInvestment inherits from Investment. So, when you use boost::shared_ptr<Investment> pInv(0,getRidOfInvestment) the compiler doesn't know 0 is of type Investment*. Hope this helps, -delfin