# performance-inefficient-vector-operation¶

Finds possible inefficient std::vector operations (e.g. push_back, emplace_back) that may cause unnecessary memory reallocations.

Currently, the check only detects following kinds of loops with a single statement body:

std::vector<int> v;
for (int i = 0; i < n; ++i) {
v.push_back(n);
// This will trigger the warning since the push_back may cause multiple
// memory reallocations in v. This can be avoid by inserting a 'reserve(n)'
// statement before the for statement.
}

• For-range loops like for (range-declaration : range_expression), the type of range_expression can be std::vector, std::array, std::deque, std::set, std::unordered_set, std::map, std::unordered_set:
std::vector<int> data;
std::vector<int> v;

for (auto element : data) {
v.push_back(element);
// This will trigger the warning since the 'push_back' may cause multiple
// memory reallocations in v. This can be avoid by inserting a
// 'reserve(data.size())' statement before the for statement.
}


## Options¶

VectorLikeClasses

Semicolon-separated list of names of vector-like classes. By default only ::std::vector is considered.