std::destroy(3)

💖 NAME 💖

std::destroy - std::destroy — no cap, that's literally the name, bestie.

Okay so welcome to std::destroy(3) from the C++ Standard Libary (yes, that's how the header spells it, and we respect the typo 💅). This page is your group-chat rundown of the destroy algorithm family, and it's lowkey iconic.

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✨ Synopsis ✨

Defined in header <memory> — like, that's the include you need, periodt.

template< class ForwardIt >
void destroy( ForwardIt first, ForwardIt last );                 (since C++17) (until C++20)

template< class ForwardIt >
constexpr void destroy( ForwardIt first, ForwardIt last );       (1) (since C++20)

template< class ExecutionPolicy, class ForwardIt >
void destroy( ExecutionPolicy&& policy, ForwardIt first,
              ForwardIt last );                                  (2) (since C++17)

1. Destroys the objects in the range [first, last), as if by

for (; first != last; ++first)
    std::destroy_at(std::addressof(*first));

2. Same as (1), but executed according to policy. This overload participates in overload resolution only if

std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true. (until C++20)

std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true. (since C++20)

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🌸 Parameters 🌸

• first, last — the range of elements to destroy.
• policy — the execution policy to use. See execution policy for details.

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🦋 Type requirements 🦋

• ForwardIt must meet the requirements of LegacyForwardIterator.
• No increment, assignment, comparison, or indirection through valid instances of ForwardIt may throw exceptions.

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🎀 Return value 🎀

(none) — literally none, bestie. It destroys and dips.

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⭐ Complexity ⭐

Linear in the distance between first and last.

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🔥 Exceptions 🔥

The overload with a template parameter named ExecutionPolicy reports errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

This is the "bestie, pay attention" part: standard policy plus thrown exception equals std::terminate, and other policies are implementation-defined. Not me making it dramatic — that's the actual rule. 😭

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👑 Possible implementation 👑

template<class ForwardIt>
constexpr // since C++20
void destroy(ForwardIt first, ForwardIt last)
{
    for (; first != last; ++first)
        std::destroy_at(std::addressof(*first));
}

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💜 Example 💜

The following example demonstrates how to use destroy to destroy a contiguous sequence of elements.

// Run this code

#include <iostream>
#include <memory>
#include <new>

struct Tracer
{
    int value;
    ~Tracer() { std::cout << value << " destructed\n"; }
};

int main()
{
    alignas(Tracer) unsigned char buffer[sizeof(Tracer) * 8];

    for (int i = 0; i < 8; ++i)
        new(buffer + sizeof(Tracer) * i) Tracer{i}; //manually construct objects

    auto ptr = std::launder(reinterpret_cast<Tracer*>(buffer));

    std::destroy(ptr, ptr + 8);
}

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🌈 Output 🌈

0 destructed
1 destructed
2 destructed
3 destructed
4 destructed
5 destructed
6 destructed
7 destructed

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🫶 See also 🫶

• destroy_n — destroys a number of objects in a range (C++17) (function template)
• destroy_at — destroys an object at a given address (C++17) (function template)
• ranges::destroy — destroys a range of objects (C++20) (niebloid)

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That's the whole page, bestie! Source: http://cppreference.com, version/date: 2024.06.10. Now go destroy those objects responsibly, mwah 💅✨