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

 

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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) 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*) 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

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void shrink_to_fit();		(since C++11)

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 " << 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 " << s.size() << '\n';
    s.clear();
    std::cout << "Capacity after clear() is " << s.capacity() << " and size " << s.size() << '\n';
    s.shrink_to_fit();
    std::cout << "Capacity after shrink_to_fit() is " << s.capacity() << " and size " << 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)