Re: singleton question

From:

Leigh Johnston <leigh@i42.co.uk>

Newsgroups:

comp.lang.c++

Date:

Wed, 02 Mar 2011 17:34:38 +0000

Message-ID:

<wdGdnaBew8wx4vPQnZ2dnUVZ8jqdnZ2d@giganews.com>

On 02/03/2011 17:33, Victor Bogado wrote:

On Mar 2, 2:28 pm, Victor Bogado<bog...@gmail.com> wrote:

On Mar 2, 12:31 pm, Leigh Johnston<le...@i42.co.uk> wrote:

On 02/03/2011 15:25, Victor Bogado wrote:

On Feb 24, 12:23 pm, kathy<yqin...@yahoo.com> wrote:

...

template<class T> T* CSingleton<T>::m_pInstance=NULL;
template<class T> T* CSingleton<T>::GetInstance()
{
if(!m_pInstance)
m_pInstance = new T;

Also This is not thread safe, you could have a race condition that
would end up with 2 instances. The best solution is to use the
instance as a static local in the instance method. The standard says
that it will be instantiated before the first call.

No; such a static will be instantiated *during* the first call however
you still have a race condition with a local static in a multi-threaded
situation.

/Leigh

This would have a race condition? I was under the impression that the
instantiation in that case would be atomic, but I never read the
standard myself, so I could be wrong :P.

the code should be :

static SingletonType& SingletonType::instance()
{
static SingletonType instance;
return instance;
}

:P

Not thread-safe. :p

/Leigh