[Qt-interest] Placement new in Qt

[Eric Clark]

Hello All,


I noticed in the QList class that they are using the placement new operator. Does anyone know what Qt expects this to do?



template <typename T>

Q_INLINE_TEMPLATE void QList<T>::node_construct(Node *n, const T &t) {

    if (QTypeInfo<T>::isLarge || QTypeInfo<T>::isStatic) n->v = new T(t);

    else if (QTypeInfo<T>::isComplex) new (n) T(t);

    else *reinterpret_cast<T*>(n) = t;

}



In the second line of the function:



else if (QTypeInfo<T>::isComplex) new (n) T(t);



What does Qt expect it to do? Does it expect realloc to get called, or does it just expect "n" to be returned?



Thanks,

Eric

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