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

 

C++

Language

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Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

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Technical Specifications

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::operator= basic_string::assign basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (C++11) basic_string::back (C++11) 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) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (C++11)

Operations basic_string::clear basic_string::insert basic_string::erase basic_string::push_back basic_string::pop_back (C++11) basic_string::append basic_string::operator+= basic_string::compare basic_string::starts_with (C++20) basic_string::ends_with (C++20) basic_string::replace basic_string::substr basic_string::copy basic_string::resize basic_string::swap 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 Constants basic_string::npos

Non-member functions operator+ swap(std::basic_string) operator""s (C++14) 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 conversion (C++11) stoistolstoll stoulstoull stofstodstold to_string to_wstring Helper classes hash<std::string>hash<std::wstring>hash<std::u32string>hash<std::u16string>hash<std::u8string> (C++11)(C++11)(C++11)(C++11)(C++20) hash<std::pmr::string>hash<std::pmr::wstring>hash<std::pmr::u32string>hash<std::pmr::u16string>hash<std::pmr::u8string> (C++20)(C++20)(C++20)(C++20)(C++20) Deduction guides(C++17)

 

void shrink_to_fit();		(since C++11) (until C++20)
constexpr void shrink_to_fit();		(since C++20)

Requests the removal of unused capacity.

It is a non-binding request to reduce capacity() to size(). It depends on the implementation if the request is fulfilled.

If (and only if) reallocation takes place, all pointers, references, and iterators are invalidated.

Parameters

(none)

Return value

(none)

Complexity

(unspecified)	(until C++17)
Linear in the size of the string	(since C++17)

Example

Run this code

#include <iostream>
#include <string>
 
int main()
{
    std::string s;
    std::cout << "Default-constructed capacity is " << s.capacity() 
        << " and size is " << s.size() << '\n';
    for (int i=0; i<42; i++)
        s.append(" 42 ");
    std::cout << "Capacity after a couple of appends is " << s.capacity() 
        << " and size is " << s.size() << '\n';
    s.clear();
    std::cout << "Capacity after clear() is " << s.capacity() 
        << " and size is " << s.size() << '\n';
    s.shrink_to_fit();
    std::cout << "Capacity after shrink_to_fit() is " << s.capacity() 
        << " and size is " << s.size() << '\n';
}

Possible output:

Default-constructed capacity is 15 and size 0
Capacity after a couple of appends is 240 and size 168
Capacity after clear() is 240 and size 0
Capacity after shrink_to_fit() is 15 and size 0

See also

sizelength	returns the number of characters (public member function)
capacity	returns the number of characters that can be held in currently allocated storage (public member function)