Are std::vector Elements Guaranteed to Be Contiguous?

Contiguity of std::vector Elements

The question arises whether std::vector elements are guaranteed to be contiguous, enabling the use of the vector's first element pointer as a C-array. Despite the lack of an explicit guarantee in the C 98 standard, it was difficult to meet the std::vector requirements without contiguity.

The C 0x standard rectified this omission, as indicated in n2798:

"A vector is a sequence container that supports ... elements of a vector are stored contiguously, meaning that if v is a vector where T is some type other than bool, then it obeys the identity &v[n] == &v[0] n for all 0 <= n < v.size()."

This confirms that std::vector elements are indeed stored contiguously, permitting the use of a pointer to the first element as a C-array:

std::vector values;
// ... fill up values

if (!values.empty()) {
    int *array = &values[0];
    for (int i = 0; i < values.size(); ++i) {
        int v = array[i];
        // do something with 'v'
    }
}
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