# std::get_temporary_buffer

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< cpp‎ | memory

Defined in header `<memory>` |  |
template< class T > std::pair <T*, std::ptrdiff_t > get_temporary_buffer( std::ptrdiff_t count ); |  | (until C++11)
template< class T > std::pair <T*, std::ptrdiff_t > get_temporary_buffer( std::ptrdiff_t count ) noexcept; |  | (since C++11) (deprecated in C++17) (removed in C++20)

If count is negative or zero, does nothing.

Otherwise, requests to allocate uninitialized contiguous storage for count adjacent objects of type `T`. The request is non-binding, and the implementation may instead allocate the storage for any other number of (including zero) adjacent objects of type `T`.

It is implementation-defined whether over-aligned types are supported. | (since C++11)

### Parameters

count | - | the desired number of objects

### Return value

A std::pair, the member `first` is a pointer to the beginning of the allocated storage and the member `second` is the number of objects that fit in the storage that was actually allocated.

If count <= 0 or allocated storage is not enough to store a single element of type `T`, the member `first` of the result is a null pointer and the member `second` is zero.

### Notes

This API was originally designed with the intent of providing a more efficient implementation than the general-purpose operator new, but no such implementation was created and the API was deprecated and removed.

### Example

Run this code

    #include <algorithm>
    #include <iostream>
    #include <iterator>
    #include <memory>
    #include <string>

    int main()
    {
        const std::string s[] = {"string", "1", "test", "..."};
        const auto p = std::get_temporary_buffer<std::string>(4);
        // requires that p.first is passed to return_temporary_buffer
        // (beware of early exit points and exceptions), or better use:
        std::unique_ptr<std::string, void(*)(std::string*)> on_exit(p.first,
        [](std::string* p)
        {
            std::cout << "returning temporary buffer...\n";
            std::return_temporary_buffer(p);
        });

        std::copy(s, s + p.second,
                  std::raw_storage_iterator<std::string*, std::string>(p.first));
        // has same effect as: std::uninitialized_copy(s, s + p.second, p.first);
        // requires that each string in p is individually destroyed
        // (beware of early exit points and exceptions)

        std::copy(p.first, p.first + p.second,
                  std::ostream_iterator<std::string>{std::cout, "\n"});

        std::for_each(p.first, p.first + p.second, [](std::string& e)
        {
            e.~basic_string<char>();
        }); // same as: std::destroy(p.first, p.first + p.second);

        // manually reclaim memory if unique_ptr-like technique is not used:
        // std::return_temporary_buffer(p.first);
    }

Output:

    string
    1
    test
    ...
    returning temporary buffer...

### 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 425 | C++98 | the behavior when count <= 0 was unclear | made clear
LWG 2072 | C++98 | it was not allowed to allocate insufficient memory | allowed

### See also

return_temporary_buffer (deprecated in C++17)(removed in C++20) | frees uninitialized storage (function template)
allocate_at_least [static] (C++23) | allocates storage at least as large as the requested size via an allocator (public static member function of `std::allocator_traits<Alloc>`)

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