# reserve-candidates
Finds places that could use a `reserve()` call.
Whenever you know how many elements a container will hold you should reserve
space in order to avoid repeated memory allocations.
#### Trivial example missing reserve()
QList<int> ages;
// list.reserve(people.size());
for (auto person : people)
list << person.age();
Example where reserve shouldn't be used:
QList<int> list;
for (int i = 0; i < 1000; ++i) {
// reserve() will be called 1000 times, meaning 1000 allocations
// whilst without a reserve the internal exponential growth algorithm would do a better job
list.reserve(list.size() + 2);
for (int j = 0; j < 2; ++j) {
list << m;
}
}
#### Supported containers
`QVector`, `std::vector`, `QList`, `QSet` and `QVarLengthArray`
#### Pitfalls
Rate of false-positives is around 15%. Don't go blindly calling `reserve()` without proper analysis.
In doubt don't use it, all containers have a growth curve and usually only do log(N) allocations
when you append N items.
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