Invalid conversion from and to void * when using ibpp in C ++

One of my class members is of void *

type:

void * conn;

      

        
        
        
      

    

In the Connection

method, I established a database connection Firebird

and set a member conn

like this:

IBPP::Database conn = IBPP::DatabaseFactory(host, dbname, user, pass);
conn->Connect();
this->conn = static_cast<void *>(conn);

      

        
        
        
      

    

This way works well for several other databases, but breaks when I try to use it with Firebird

. So here's what's going on. In another method, I use a member conn

to retrieve data from a specific database. When it comes to Firebird

, I do it like this:

IBPP::Transaction tr = IBPP::TransactionFactory(static_cast<IBPP::Database>(this->conn));

      

        
        
        
      

    

However, this line of code shows an error:

error: invalid conversion from 'void *' to 'IBPP::IDatabase *'

      

        
        
        
      

    

I don't know what I am doing wrong.

EDIT

Here are some code snippets from ibpp.h

:

...
class IDatabase;
typedef Ptr<IDatabase> Database;
...
class IDatabase{
    public:
        virtual const char * ServerName() const = 0;
        virtual const char * DatabaseName() const = 0;
        ...
        virtual void Connect() = 0;
        ...
}

      

        
        
        
      

    

EDIT

Here's a playable test file:

#define IBPP_LINUX
#include <ibpp.h>

int main(){
    //#1. No errors
    IBPP::Database conn = IBPP::DatabaseFactory("localhost","/var/lib/firebird/2.5/data/reestr.fdb","SYSDBA","root");
    conn->Connect();
    conn->Disconnect();
    //end of #1.
    //#2. Here we get errors.
    void * cn;
    IBPP::Database conn2 = IBPP::DatabaseFactory("localhost","/var/lib/firebird/2.5/data/reestr.fdb","SYSDBA","root");
    conn2->Connect();
    cn = static_cast<void *>(conn2);
    conn2->Disconnect();
    return 0;
}

      

        
        
        
      

    

and this is the error message I get when I try to compile it:

error: invalid static_cast from type IBPP::Database 
{aka IBPP::Ptr<IBPP::IDatabase>} to type void *

      

        
        
        
      

    

The error message points to this line of code:

cn = static_cast<void *>(conn2);