https://bugs.kde.org/show_bug.cgi?id=359305
--- Comment #1 from Sergio Martins <smart...@kde.org> ---
Your first example allocates once (due to keys() call), and it should allocate
0.
Use instead: for (auto it = someMap.cbegin(), end = someMap.cend(); it != end;
++it)
Your second example allocates twice (due to keys call) and it should allocate
once, construct the set manually instead.
This is what happens when you call keys():
template <class Key, class T>
Q_OUTOFLINE_TEMPLATE QList<Key> QHash<Key, T>::keys() const
{
QList<Key> res;
res.reserve(size());
const_iterator i = begin();
while (i != end()) {
res.append(i.key());
++i;
}
return res;
}
You would be iterating twice instead of iterating the map directly.
I can update the README and make it more clear.
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