Re: [Boost-users] is read/write mutex example correct

From: Kevin Heifner (heifnerk_at_[hidden])
Date: 2008-05-14 09:55:34

Selçuk Giray Özdamar wrote:
>        const T& at(int index) const;

This doesn't look good.

>        T& at(int index);

Or this.

> private:
>        std::vector<T> m_buffer;
>        boost::shared_mutex rw_mutex;
> };

> template <typename T>
> const T& EntityUpdateBuffer<T>::at( int index ) const
> {
>        // acquire lock
>        read_lock lock(rw_mutex);
>        return m_buffer.at(index);
> }

The problem with this code is that you are returning a reference 
to data that might be immediately invalidated.  A push_back via 
another thread can cause the referenced memory to no longer be valid.

> template <typename T>
> T& EntityUpdateBuffer<T>::at( int index )
> {
>        // acquire lock
>        read_lock lock(rw_mutex);
>        return m_buffer.at(index);
> }

Same problem.

KevinH
-- 
Kevin Heifner  heifner @ ociweb.com  http://heifner.blogspot.com
           Object Computing, Inc. (OCI) www.ociweb.com