Re: auto_ptr who is right?

From:

Barry <dhb2000@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 02 Sep 2007 21:38:37 +0800

Message-ID:

<fbeee0$3gp$1@aioe.org>

peter koch wrote:

On 2 Sep., 15:19, Barry <dhb2...@gmail.com> wrote:

struct A
{
    void Print() const {
       cout << "Print" << endl;
    }

};

auto_ptr<A> Get()
{
    new A; // (1)
    // auto_ptr<A>(new A); // (2) works fine

Don't you respect your compilers warnings? This should not compile
without a warning, and you do not return anything - whats returned is
rubbish.

sorry, I didn't compile this code, I just make a mimic example
after I post this thread, I compile this code (add return), and found it
work also on MSVC8

}

int main()
{
auto_ptr<A> p = Get();
p->Print();

Here you dereference garbage. Garbage in means garbase out.

/Peter

[snip]

Well, this one really crashes!

#include <memory>
#include <iostream>
#include <string>

using namespace std;

struct Pizza
{
     Pizza(string const& name) : name_(name) {}
     void Show() const
     {
         cout << name_ << " Pizza" << endl;
     }
private:
     string name_;
};

struct Pie
{
     Pie(string const& name) : name_(name) {}
     void Show() const
     {
         cout << name_ << " Pie" << endl;
     }
private:
     string name_;
};

class AbstractFactory
{
public:
     virtual auto_ptr<Pizza> CreatePizza() = 0;

     virtual ~AbstractFactory() {}
};

class NestFactory
     : public AbstractFactory
{
     virtual auto_ptr<Pizza> CreatePizza()
     {
         return new Pizza("Nest");
     }
};

int main()
{
     auto_ptr<AbstractFactory> pFactory(new NestFactory);
     auto_ptr<Pizza> pPizza = pFactory->CreatePizza();
     pPizza->Show();
}

--
Thanks
Barry