ITER.ADVANCE.NONADJACENT

Advancing iterator by a distance of more than 1

A defect will be reported for use of the following functions to advance an iterator with the last argument other than -1, 0, 1:

• operator+

• operator+=

• operator-

• operator-=

• std::prev

• std::next

Vulnerability and risk

Buffer overflow is the most common security vulnerability, and this defect is a subclass of that vulnerability: C++ STL specific.

Vulnerable code example

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#include <vector>
#include <iterator>
 
void noncompliant (const std::vector<int> & c)
{
  const size_t dist = 20;
  auto it = std::next (c.begin (), dist);
}

Klocwork reports defect ITER.ADVANCE.NONADJACENT on line 7 stating "Iterator 'c.begin()' is incremented or decremented by more than 1 at line 7". Iterator 'it' is advanced by a distance of 20.

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#include <algorithm>
 
void compliant (const std::vector<int> & c)
{
  const size_t dist = 20;
  auto it = std::next (c.begin (), std::min (dist, c.size ()));
}

External guidance

• CERT CTR55-CPP: Do not use an additive operator on an iterator if the result would overflow