std::basic_string<CharT,Traits,Allocator>::max_size

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Strings library

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::~basic_string basic_string::operator= basic_string::assign basic_string::assign_range (C++23)   basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (DR*) basic_string::back (DR*) basic_string::data basic_string::c_str basic_string::operator  basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of

Modifiers basic_string::clear basic_string::insert basic_string::insert_range (C++23) basic_string::erase basic_string::push_back basic_string::pop_back (DR*) basic_string::append basic_string::append_range (C++23) basic_string::operator+= basic_string::replace basic_string::replace_with_range (C++23) basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23)  basic_string::swap Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (DR*) Operations basic_string::compare basic_string::starts_with (C++20) basic_string::ends_with (C++20) basic_string::contains (C++23) basic_string::substr

Constants basic_string::npos Non-member functions operator+ swap(std::basic_string) erase(std::basic_string)erase_if(std::basic_string) (C++20)(C++20) I/O operator<<operator>> getline Comparison operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) Numeric conversions stoistolstoll (C++11)(C++11)(C++11) stoulstoull (C++11)(C++11)  stofstodstold (C++11)(C++11)(C++11) to_string (C++11) to_wstring (C++11) Literals operator""s (C++14) Helper classes hash<std::basic_string> (C++11) Deduction guides(C++17)

 

size_type max_size()const;		(noexcept since C++11) (constexpr since C++20)

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

Parameters

(none)

Return value

Maximum number of characters.

Complexity

Constant.

Example

Run this code

#include <array>#include <climits>#include <iomanip>#include <iostream>#include <locale>#include <string>#include <typeinfo>   #include <boost/core/demangle.hpp>   template<typename T>void print_basic_string_max_size(){std::basic_string<T> s;auto max_size = s.max_size();std::cout.imbue(std::locale("en_US.UTF-8"));std::cout<<"basic_string<"<< boost::core::demangle(typeid(T).name())<<">:\n\t"<< max_size <<" = ";std::cout<<std::setprecision(3)<<(double) max_size <<" = ";std::cout.imbue(std::locale("C"));std::cout<<std::hex<<std::setfill('0')<<"0x"<<std::setw(sizeof(typename decltype(s)::size_type)<<1)<< max_size <<'\n'<<std::dec;};   int main(){std::cout<<"Pointer size: "<<CHAR_BIT* sizeof(void*)<<" bits\n""Maximum sizes:\n";   print_basic_string_max_size<char>(); print_basic_string_max_size<char16_t>(); print_basic_string_max_size<char32_t>(); print_basic_string_max_size<wchar_t>(); print_basic_string_max_size<long>();   using CharT =std::array<char, 01232>; print_basic_string_max_size<CharT>();}

Possible output:

Pointer size: 64 bits Maximum sizes: basic_string<char>: 9,223,372,036,854,775,807 = 9.22e+18 = 0x7fffffffffffffff basic_string<char16_t>: 4,611,686,018,427,387,903 = 4.61e+18 = 0x3fffffffffffffff basic_string<char32_t>: 2,305,843,009,213,693,951 = 2.31e+18 = 0x1fffffffffffffff basic_string<wchar_t>: 2,305,843,009,213,693,951 = 2.31e+18 = 0x1fffffffffffffff basic_string<long>: 1,152,921,504,606,846,975 = 1.15e+18 = 0x0fffffffffffffff basic_string<std::array<char, 666ul>>: 13,848,906,962,244,407 = 1.38e+16 = 0x00313381ec031337

See also

sizelength	returns the number of characters (public member function)
sizelength	returns the number of characters (public member function of std::basic_string_view<CharT,Traits>)