NAME¶

std::vector::data - std::vector::data

Synopsis¶

T* data(); (1) (noexcept since C++11)
(constexpr since C++20)
const T* data() const; (2) (noexcept since C++11)
(constexpr since C++20)

Returns pointer to the underlying array serving as element storage. The pointer is
such that range [data(), data() + size()) is always a valid range, even if the
container is empty (data() is not dereferenceable in that case).

Parameters¶

(none)

Return value¶

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

Complexity¶

Constant.

Notes¶

If size() is 0, data() may or may not return a null pointer.

Example¶

// Run this code

#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 (C++20) is a safer alternative to separated pointer/size.
span_func({container.data(), container.size()});
}

Output:¶

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.

DR Applied to Behavior as published Correct behavior
LWG 464 C++98 vector did not have this member added
function
LWG 1312 C++98 the return type were pointer and changed to T* and const T*
const_pointer respectively

See also¶

front access the first element
(public member function)
back access the last element
(public member function)
size returns the number of elements
(public member function)
span a non-owning view over a contiguous sequence of objects
(C++20) (class template)
data obtains the pointer to the underlying array
(C++17) (function template)