std::map::max_size

size_type max_size() const;		(until C++11)
size_type max_size() const noexcept;		(since C++11)

Returns the maximum number of elements the container is able to hold due to system or library implementation limitations, i.e. std::distance(begin(), end()) for the largest container.

Parameters

(none)

Return value

Maximum number of elements.

Complexity

Constant.

Notes

This value typically reflects the theoretical limit on the size of the container. At runtime, the size of the container may be limited to a value smaller than max_size() by the amount of RAM available.

Example

Run this code

#include <iostream>
#include <map>

int main()
{
    std::map<char,char> s;
    std::cout << "Maximum size of a 'map' is " << s.max_size() << "\n";
}

Possible output:

Maximum size of a 'map' is 18446744073709551615

Language
Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

array (C++11)
vector
deque
forward_list (C++11)
list
set
multiset
map
multimap
unordered_set (C++11)
unordered_multiset (C++11)
unordered_map (C++11)
unordered_multimap (C++11)
stack
queue
priority_queue
span (C++20)