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Consequently, the values of existing iterators may be invalidated [Kalev 99]. Using invalid iterators yields undefined results.

Non-Compliant Code Example

In this example, the iterator pos is invalidated after the call to insert, and subsequent loop iterations have undefined behavior.

double data[5] = { 2.3, 3.7, 1.4, 0.8, 9.6 };

deque<double> d;
deque<double>::iterator pos = d.begin();

for (size_t i = 0; i < 5; ++i) {
  d.insert(pos++, data[i] + 41);
}

Compliant Solution 1

Update pos each time insert is called to keep the iterators valid, and then increment it:

double data[5] = { 2.3, 3.7, 1.4, 0.8, 9.6 };

deque<double> d;
deque<double>::iterator pos = d.begin();

for (size_t i = 0; i < 5; ++i) {
  pos = d.insert(pos, data[i] + 41);
  ++pos;
}

Compliant Solution 2

Use one of the STL algorithms.

double data[5] = { 2.3, 3.7, 1.4, 0.8, 9.6 };
deque<double> d;

transform(data, data+5,
    inserter(d, d.begin()),
    bind2nd(plus<int>(), 41));

Risk Assessment

Using invalid iterators yields undefined results.

Bibliography

[Meyers 01] Item 43: Prefer algorithm calls to hand-written loops.
[Sutter 04] Item 84: Prefer algorithm calls to handwritten loops.
[Kalev 99] ANSI/ISO C++ Professional Programmer's Handbook.
[ISO/IEC 14882-2003] Section 24: Iterators Library.

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      06. Containers (CTR)      ARR33CTR33-CPP. Guarantee that copies are made into storage of sufficient size