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Returns a pointer to the underlying array serving as element storage. The pointer is such that range [data(), data() + size() ) is always a valid range

If *this is empty, data() is not dereferenceable.

[edit] Return value

Pointer to the underlying element storage. For non-empty containers, the returned pointer compares equal to the address of the first element.

[edit] Complexity

Constant.

[edit] Notes

If *this is empty, data() may or may not return a null pointer.

[edit] Example

#include <cstddef>
#include <iostream>
#include <span>
#include <vector>
 
void pointer_func(const int* p, std::size_t size)
{
 std::cout << "data = ";
 for (std::size_t i = 0; i < size; ++i)
 std::cout << p[i] << ' ';
 std::cout << '\n';
}
 
void span_func(std::span <const int> data) // since C++20
{
 std::cout << "data = ";
 for (const int e : data)
 std::cout << e << ' ';
 std::cout << '\n';
}
 
int main()
{
 std::vector <int> container{1, 2, 3, 4};
 
 // Prefer container.data() over &container[0]
 pointer_func(container.data(), container.size());
 
 // std::span is a safer alternative to separated pointer/size.
 span_func({container.data(), container.size()});
}

data = 1 2 3 4
data = 1 2 3 4

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also

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