c++ - Conversion of boost::scoped_ptr to reference fails -

can explain why conversion reference type fails in example? want use boost::scoped_ptras workaround missing std::unique_ptr.

struct a{};  struct b {     b(boost::scoped_ptr<a>& a) { m_a.swap(a); }     boost::scoped_ptr<a> m_a; };  void f() {     b b(boost::scoped_ptr<a>(new a)); } 

gcc fail with:

note:   no known conversion argument 1 ‘boost::scoped_ptr<a>’  ‘boost::scoped_ptr<a>&’ 

design rationale (why use scoped_ptr in first place):

• don't want use raw pointers because of exception safety (real-world scenario involves multiple objects passed)
• don't want use auto_ptr because of possible silent deallocation fails
• can't use unique_ptr because still stuck c++03
• use of shared_ptr may valid workaround seems unclean because nothing shared, really

you can't bind non-const lvalue references temporaries, here

b b(boost::scoped_ptr<a>(new a)); 

you can fix particular problem passing lvalue:

void f() {        boost::scoped_ptr<a> a(new a);     b b(a); }