checked_delete

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## checked_delete

### Authors

- Beman Dawes
- Dave Abrahams
- Vladimir Prus
- Rainer Deyke
- John Maddock

### Overview

The header `<boost/checked_delete.hpp>` defines two function templates, `checked_delete` and `checked_array_delete`, and two class templates, `checked_deleter` and `checked_array_deleter`.

The C++ Standard allows, in 5.3.5/5, pointers to incomplete class types to be deleted with a delete-expression. When the class has a non-trivial destructor, or a class-specific operator delete, the behavior is undefined. Some compilers issue a warning when an incomplete type is deleted, but unfortunately, not all do, and programmers sometimes ignore or disable warnings.

A particularly troublesome case is when a smart pointer's destructor, such as `boost::scoped_ptr<T>::~scoped_ptr`, is instantiated with an incomplete type. This can often lead to silent, hard to track failures.

The supplied function and class templates can be used to prevent these problems, as they require a complete type, and cause a compilation error otherwise.

### Synopsis

    namespace boost
    {
        template<class T> void checked_delete(T * p);
        template<class T> void checked_array_delete(T * p);
        template<class T> struct checked_deleter;
        template<class T> struct checked_array_deleter;
    }

### checked_delete

#### template<class T> void checked_delete(T * p);

- Requires: `T` must be a complete type. The expression `delete p` must be well-formed.
- Effects: `delete p;`

### checked_array_delete

#### template<class T> void checked_array_delete(T * p);

- Requires: `T` must be a complete type. The expression `delete [] p` must be well-formed.
- Effects: `delete [] p;`

### checked_deleter

    template<class T> struct checked_deleter
    {
        typedef void result_type;
        typedef T * argument_type;
        void operator()(T * p) const;
    };

#### void checked_deleter<T>::operator()(T * p) const;

- Requires: `T` must be a complete type. The expression `delete p` must be well-formed.
- Effects: `delete p;`

### checked_array_deleter

    template<class T> struct checked_array_deleter
    {
        typedef void result_type;
        typedef T * argument_type;
        void operator()(T * p) const;
    };

#### void checked_array_deleter<T>::operator()(T * p) const;

- Requires: `T` must be a complete type. The expression `delete [] p` must be well-formed.
- Effects: `delete [] p;`

### Acknowledgements

The function templates `checked_delete` and `checked_array_delete` were originally part of `<boost/utility.hpp>`, and the documentation acknowledged Beman Dawes, Dave Abrahams, Vladimir Prus, Rainer Deyke, John Maddock, and others as contributors.