Calling constructor of a template class

Question

I have a container class which has a pre allocated buffer. I am calling memset() to use pre-allocated memory to create my objects. Since I am not using new, the constructor is not called.

Here is a simplified version of the add function

 template<typename T>
 T* CContainer<T>::Add()
 {
memset(&m_pBuffer[index],0,index);
T* pReturnValue = reinterpret_cast<T*> ( &m_pBuffer[index] );

return pReturnValue;
 }

Any way to call the constructor of template class T.

Thanks for your help.

Use "placement new". [This](http://stackoverflow.com/questions/222557/what-uses-are-there-for-placement-new) has a good explanation. — cole, Feb 02 '13 at 08:52

Stefan Dragnev · Accepted Answer · 2013-02-02T09:12:38.120

3

To call the constructor of an object in an existing piece of memory use placement new.

In your case add this line right before the return statement:

new (pReturnValue) T;

To destroy the instance, call the destructor explicitly:

pReturnValue->~T();

edited Feb 02 '13 at 09:12

answered Feb 02 '13 at 08:48

Stefan Dragnev

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Thanks guys, is there a way to call the destructor when removing an object and reassigning its memory? – Codesmith Feb 02 '13 at 09:02
@Codesmith: added edit for destructor call. If you find this post acceptable, please mark it as an asnwer to your question. – Stefan Dragnev Feb 02 '13 at 09:13

Calling constructor of a template class

1 Answers1