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Difference between revisions of "cpp/memory/destroy"

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< cpp‎ | memory
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m ({{range}}, fmt, {{c}})
 
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{{cpp/memory/navbar}}
 
{{cpp/memory/navbar}}
 
{{dcl begin}}
 
{{dcl begin}}
−
{{dcl header | memory}}
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{{dcl header|memory}}
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{{dcl | since=c++17 | num= 1 |1=
+
{{dcl rev multi|num=1
 +
|since1=c++17|dcl1=
 
template< class ForwardIt >
 
template< class ForwardIt >
 
void destroy( ForwardIt first, ForwardIt last );
 
void destroy( ForwardIt first, ForwardIt last );
 +
|since2=c++20|dcl2=
 +
template< class ForwardIt >
 +
constexpr void destroy( ForwardIt first, ForwardIt last );
 
}}
 
}}
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{{dcl | since=c++17 | num= 2 |1=
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{{dcl|num=2|since=c++17|
 
template< class ExecutionPolicy, class ForwardIt >
 
template< class ExecutionPolicy, class ForwardIt >
−
void destroy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last );}}
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void destroy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last );
 +
}}
 
{{dcl end}}
 
{{dcl end}}
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@1@ Destroys the  objects in the range {{tt|[first, last)}}, as if by
+
@1@ Destroys the  objects in the range {{range|first|last}}, as if by
 
{{source|1=
 
{{source|1=
 
for (; first != last; ++first)
 
for (; first != last; ++first)
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  std::destroy_at(std::addressof(*first));
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    std::destroy_at(std::addressof(*first));
 
}}
 
}}
  
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@2@ Same as {{v|1}}, but executed according to {{tt|policy}}. This overload does not participate in overload resolution unless {{c|std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>}} is true.
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@2@ Same as {{v|1}}, but executed according to {{c|policy}}. {{cpp/algorithm/parallel overload precondition}}
  
 
===Parameters===
 
===Parameters===
 
{{par begin}}
 
{{par begin}}
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{{par | first, last | the range of elements to destroy}}
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{{par|first, last|the range of elements to destroy}}
 
{{par exec pol}}
 
{{par exec pol}}
 
{{par hreq}}
 
{{par hreq}}
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{{par req concept | ForwardIt | ForwardIterator}}
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{{par req named|ForwardIt|ForwardIterator}}
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{{par req | No increment, assignment, comparison, or indirection through valid instances of {{tt|ForwardIt}} may throw exceptions.}}
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{{par req|No increment, assignment, comparison, or indirection through valid instances of {{tt|ForwardIt}} may throw exceptions.}}
 
{{par end}}
 
{{par end}}
  
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===Complexity===
 
===Complexity===
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Linear in the distance between {{tt|first}} and {{tt|last}}.
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Linear in the distance between {{c|first}} and {{c|last}}.
  
 
===Exceptions===
 
===Exceptions===
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===Possible implementation===
 
===Possible implementation===
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{{eq fun | 1=
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{{eq fun|1=
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template< class ForwardIt >
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template<class ForwardIt>
−
void destroy( ForwardIt first, ForwardIt last )
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constexpr // since C++20
 +
void destroy(ForwardIt first, ForwardIt last)
 
{
 
{
−
  for (; first != last; ++first)
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    for (; first != last; ++first)
−
    std::destroy_at(std::addressof(*first));
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        std::destroy_at(std::addressof(*first));
 
}
 
}
 
}}
 
}}
  
 
===Example===
 
===Example===
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{{example
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{{cpp/memory/destroy example|destroy}}
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}}
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===See also===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc | cpp/memory/dsc destroy_n}}
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{{dsc inc|cpp/memory/dsc destroy_n}}
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{{dsc inc | cpp/memory/dsc destroy_at}}
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{{dsc inc|cpp/memory/dsc destroy_at}}
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{{dsc inc|cpp/memory/ranges/dsc destroy}}
 
{{dsc end}}
 
{{dsc end}}
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 +
{{langlinks|es|ja|ru|zh}}

Latest revision as of 09:39, 13 June 2023

 
C++
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
Dynamic memory management
Uninitialized memory algorithms
Constrained uninitialized memory algorithms
Allocators
Garbage collection support
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)



 
Defined in header <memory>
(1)
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 );
 (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)

Contents

[edit] Parameters

first, last - the range of elements to destroy
policy - the execution policy to use. See execution policy for details.
Type requirements
-
ForwardIt must meet the requirements of LegacyForwardIterator.
-
No increment, assignment, comparison, or indirection through valid instances of ForwardIt may throw exceptions.

[edit] Return value

(none)

[edit] Complexity

Linear in the distance between first and last.

[edit] 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.

[edit] 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));
}

[edit] 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);
}

Output: 

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

[edit] See also

(C++17)
 destroys a number of objects in a range
(function template) [edit]
(C++17)
 destroys an object at a given address
(function template) [edit]
(C++20)
 destroys a range of objects
(niebloid)[edit]
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