Is std::vector Element Memory Contiguous in C ?

Memory Contiguity of std::Vector Elements

Concerned developers often raise the question of whether elements within a std::vector are guaranteed to be contiguous. This property determines whether it's permissible to treat the pointer to the first element as a C-style array.

Standard Provisions

Initially, the C 98 standard neglected to specify this aspect. However, subsequent technical reports (TR) rectified this oversight, and the forthcoming C 0x standard will incorporate it as an explicit requirement.

TR Specifications

N2798, a draft of C 0x, postulates:

"A vector is a sequence container that supports random access iterators ... The 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()."

Example

Based on this specification, consider the following code snippet:

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'
    }
}

The C   standard guarantees that this code will function as intended by allowing direct memory access to the vector's elements.
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