Effective C + +--resource management

13. Managing Resources with objects

    void f ()    {        investment* PINV = Createinvestment ();                ...        Delete Pinv;    }

• There is a problem with the above code: An exception occurred before the delete, causing the PINV to be deleted, causing a resource leak.

• Workaround: RAII Resource acquisition is initialization resource acquisition time is initialized

using smart pointers, the code is as follows:

    void f ()    {        auto_ptr<investment> pinv (Createinvestment ());    }

14. Beware of copying behavior in resource management classes

When a Raii object is copied, it is generally possible to select the following.

• Prohibit assignment
• Reference count for the underlying resource
• Replicating underlying resources
• Transferring ownership of underlying resources

Share_ptr allows you to specify a remove device

15. Provide access to the original resource in the resource management class

Auto_ptr,share_ptr provides a get function to get the original resource.
When customizing Raii, you can use both display and implicit conversions.
Implicit conversion: operator Fonthandle () const {return F;}

16. Use the same form when using new and delete in pairs

New Using Delete
New [] using delete []
The memory model of new [] may be: number of arrays + elements of each array. Non-paired use can cause undefined behavior.
Calling delete on new [] may cause other objects to be non-destructor.
typedef usage considerations, do not define arrays

17. Placing a Newed object into a smart pointer with a separate statement

    int priority ();    void Processwidget (shared_ptr<widget> pw, int priority);    Processwidget (shrare_ptr<widget> (new Widget), priority ());

The above code issues are as follows:

possible order of execution is

Execute New Widget
Call priority
Call Share_ptr

if the priority call exception causes the new widget resource to be compromised.

here's how to fix it:

Share_ptr<widget> PW (new Widget);p rocesswidget (PW, priority);

Effective C + +--resource management