performance-inefficient-vector-operation¶
Finds possible inefficient std::vector operations (e.g. push_back,
emplace_back) that may cause unnecessary memory reallocations.
It can also find calls that add element to protobuf repeated field in a loop without calling Reserve() before the loop. Calling Reserve() first can avoid unnecessary memory reallocations.
Currently, the check only detects following kinds of loops with a single statement body:
Counter-based for loops start with 0:
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.
}
SomeProto p;
for (int i = 0; i < n; ++i) {
p.add_xxx(n);
// This will trigger the warning since the add_xxx may cause multiple memory
// relloacations. This can be avoid by inserting a
// 'p.mutable_xxx().Reserve(n)' statement before the for statement.
}
For-range loops like
for (range-declaration : range_expression), the type ofrange_expressioncan bestd::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::vectoris considered.
-
EnableProto¶ When non-zero, the check will also warn on inefficient operations for proto repeated fields. Otherwise, the check only warns on inefficient vector operations. Default is 0.