Windows到Linux端口C ++错误

Question

I am working on porting a large c++ application from Windows to Linux and so far I've been working through the issues and replacing the Windows specific stuff with standards code.

I've come across a template that begins like this

#define IC __attribute__((inline))

template <typename object_type, typename base_type = intrusive_base>
class intrusive_ptr
{
private:
    typedef base_type base_type;
    typedef object_type object_type;
    typedef intrusive_ptr<object_type, base_type> self_type;
    typedef const object_type* (intrusive_ptr::*unspecified_bool_type) () const;

...

public:
    IC intrusive_ptr();
    IC intrusive_ptr(object_type* rhs);
    IC intrusive_ptr(self_type const& rhs);
    IC ~intrusive_ptr();
    IC self_type& operator= (object_type* rhs);
    IC self_type& operator= (self_type const& rhs);
    IC object_type& operator*() const; // original
    IC object_type* operator->() const;   // original

... 
};


#define TEMPLATE_SPECIALIZATION template <typename object_type, typename base_type>
#define _intrusive_ptr intrusive_ptr<object_type, base_type>

TEMPLATE_SPECIALIZATION
IC typename _intrusive_ptr::object_type& _intrusive_ptr::operator* () const
{
    VERIFY(m_object);
    return (*m_object);
}

TEMPLATE_SPECIALIZATION
IC typename _intrusive_ptr::object_type* _intrusive_ptr::operator->() const
{
    VERIFY(m_object);
    return (m_object);
}

I am having trouble understanding a couple of things.

What is the reason for the

typedef base_type base_type;

GCC has issues with it as it "shadows template parm 'class base_type'". Obviously there was some purpose for it and the Microsoft compiler must have allowed it.

I also have issues with the TEMPLATE_SPECIALIZATION stuff below giving errors like

error: prototype for ‘typename intrusive_ptr<object_type, base_type>::object_type& intrusive_ptr<object_type, base_type>::operator*() const’ does not match any in class ‘intrusive_ptr<object_type, base_type>’

&

error: candidate is: object_type& intrusive_ptr<object_type, base_type>::operator*() const

I am not the most proficient with c++ as it isn't my primary language but I have learned a lot so far by attempting this port and will continue to learn a lot. I'm a bit stuck on these errors at the moment and hope someone might be able to help.

Thanks.

Answer 1

The typedef for base_type is quite simple: to make the type used in the template argument list available to users of intrusive_ptr (although, since the type is actually 'private' it doesn't really much sense), the type is defined with in the template definition. The trivial fix is to change the code to become

template <typename Object_type, typename Base_type = intrusive_base>
class intrusive_ptr
{
private:
    typedef Base_type base_type;
    typedef Object_type object_type;
    // ...

I'd think that also fixes the problem with the overload: it seems the problem with not finding the correct overload is a follow-up problem of the nested type not being defined.