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Hi!
I'm trying to create a wrapper around mysql but I have a problem with
shared_ptr. Look at the following code:
#include
#include <iostream>
#include <map>
struct MYSQL {};
MYSQL* mysql_init() {
std::clog << __PRETTY_FUNCTION__ << std::endl;
return new MYSQL;
}
void mysql_close(MYSQL* m) {
std::clog << __PRETTY_FUNCTION__ << std::endl;
delete m;
}
class Connection {
boost::shared_ptr<MYSQL> m_mysql;
public:
void connect() {
m_mysql.reset(mysql_init(), mysql_close);
}
bool isConnected() const { return m_mysql.get() != 0; }
};
class ConnectionManager {
std::map m_connections;
public:
static ConnectionManager* instance() {
static ConnectionManager cm;
return &cm;
}
Connection connection(const std::string& name = "default")
{ return m_connections[name]; }
};
int main()
{
{
Connection c = ConnectionManager::instance()->connection();
std::clog << "isConnected " << c.isConnected() << std::endl;
c.connect();
std::clog << "isConnected " << c.isConnected() << std::endl;
}
Connection c = ConnectionManager::instance()->connection();
std::clog << "isConnected " << c.isConnected() << std::endl;
return 0;
}
And the output is:
isConnected 0
MYSQL* mysql_init()
isConnected 1
void mysql_close(MYSQL*)
isConnected 0
What I don't understand is why shared_ptr calls mysql_close too soon.
After all still exists a reference to Connection. I mean, mysql_close
should by called when the ConnectionManager singleton is destroyed or am
I doing something wrong.
- -- Filipe Sousa
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