std::get_deleter

 

C++

編譯器支援

自由（freestanding）與宿主（hosted）

語言

標準庫

標準庫標頭檔案

具名要求

特性測試宏 (C++20)

語言支援庫

概念庫 (C++20)

診斷庫

記憶體管理庫

超程式設計庫 (C++11)

通用工具庫

容器庫

迭代器庫

範圍庫 (C++20)

演算法庫

字串庫

文字處理庫

數值庫

日期和時間庫

輸入/輸出庫

檔案系統庫 (C++17)

併發支援庫 (C++11)

執行控制庫 (C++26)

技術規範

符號索引

外部庫

 

記憶體管理庫

voidify (僅作說明*) 未初始化記憶體演算法 uninitialized_copy uninitialized_fill uninitialized_move (C++17) uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) destroy (C++17) destroy_at (C++17) uninitialized_copy_n (C++11) uninitialized_fill_n uninitialized_move_n (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17) destroy_n (C++17) construct_at (C++20) 受約束的未初始化 記憶體演算法 ranges::uninitialized_copy (C++20) ranges::uninitialized_fill (C++20) ranges::uninitialized_move (C++20) ranges::construct_at (C++20) ranges::destroy (C++20) ranges::destroy_n (C++20) ranges::destroy_at (C++20) ranges::uninitialized_copy_n (C++20) ranges::uninitialized_fill_n (C++20) ranges::uninitialized_move_n (C++20) ranges::uninitialized_default_construct (C++20) ranges::uninitialized_value_construct (C++20) ranges::uninitialized_default_construct_n (C++20)  ranges::uninitialized_value_construct_n (C++20) C 庫 malloc calloc realloc aligned_alloc (C++17) free

分配器 allocator allocator_traits (C++11) allocation_result (C++23) allocator_arg (C++11) uses_allocator (C++11) uses_allocator_construction_args (C++20) make_obj_using_allocator (C++20) uninitialized_construct_using_allocator (C++20)  scoped_allocator_adaptor (C++11) pmr::polymorphic_allocator (C++17) 記憶體資源 pmr::memory_resource (C++17) pmr::get_default_resource (C++17) pmr::set_default_resource (C++17) pmr::new_delete_resource (C++17) pmr::null_memory_resource (C++17) pmr::synchronized_pool_resource (C++17) pmr::unsynchronized_pool_resource (C++17) pmr::monotonic_buffer_resource (C++17) pmr::pool_options (C++17) 垃圾回收支援 declare_reachable (C++11)(直到 C++23) undeclare_reachable (C++11)(直到 C++23) declare_no_pointers (C++11)(直到 C++23) undeclare_no_pointers (C++11)(直到 C++23) pointer_safety (C++11)(直到 C++23) get_pointer_safety (C++11)(直到 C++23) 未初始化儲存 raw_storage_iterator (直到 C++20*) get_temporary_buffer (直到 C++20*) return_temporary_buffer (直到 C++20*) 顯式生命週期管理 start_lifetime_asstart_lifetime_as_array (C++23)(C++23)

智慧指標 unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (直到 C++17*) owner_less (C++11) owner_less<void> (C++17) owner_hash (C++26) owner_equal (C++26) enable_shared_from_this (C++11) bad_weak_ptr (C++11) default_delete (C++11) out_ptr_t (C++23) inout_ptr_t (C++23) 低階記憶體 管理 operator new operator new[] operator delete operator delete[] get_new_handler (C++11) set_new_handler launder (C++17) bad_alloc bad_array_new_length (C++11) nothrow_t align_val_t (C++17) destroying_delete_t (C++20) new_handler nothrow 雜項 pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) is_sufficiently_aligned (C++26)

 

std::shared_ptr

成員函式

shared_ptr::shared_ptr

shared_ptr::~shared_ptr

shared_ptr::operator=

修改器

shared_ptr::reset

shared_ptr::swap

觀察器

shared_ptr::get

shared_ptr::operator*shared_ptr::operator->

shared_ptr::operator[] (C++17)

shared_ptr::use_count

shared_ptr::unique (C++20之前已棄用，C++20中移除*)

shared_ptr::operator bool

shared_ptr::owner_before

shared_ptr::owner_hash (C++26)

shared_ptr::owner_equal (C++26)

非成員函式

swap(std::shared_ptr)

make_sharedmake_shared_for_overwrite (C++20 起)

allocate_sharedallocate_shared_for_overwrite (C++20 起)

static_pointer_castdynamic_pointer_castconst_pointer_castreinterpret_pointer_cast (C++17)

get_deleter

operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

operator<<

atomic_xxx 函式 (C++20中已棄用，C++26中移除*)

輔助類

atomic<std::shared_ptr> (C++20)

hash<std::shared_ptr>

推導指南(C++17)

 

定義於標頭檔案 <memory>
template< class Deleter, class T > Deleter* get_deleter( const std::shared_ptr<T>& p ) noexcept;		(C++11 起)

訪問 p 的刪除器。如果共享指標 p 擁有一個 cv 非限定 `Deleter` 型別的刪除器（例如，如果它是用一個將刪除器作為引數的建構函式建立的），則返回一個指向該刪除器的指標。否則，返回空指標。

引數

p

-

一個需要訪問其刪除器的共享指標。

返回值

一個指向所擁有的刪除器的指標，或 nullptr。返回的指標至少在仍然存在至少一個擁有它的 shared_ptr 例項時有效。

注意

如果例如 std::weak_ptr 仍然存在，並且實現直到整個控制塊被銷燬才銷燬刪除器，則返回的指標可能比最後一個 shared_ptr 例項壽命更長。

示例

演示 std::shared_ptr 的刪除器獨立於 shared_ptr 的型別。

執行此程式碼

#include <iostream>
#include <memory>
 
struct Foo { int i; };
void foo_deleter(Foo* p)
{
    std::cout << "foo_deleter called!\n";
    delete p;
}
 
int main()
{
    std::shared_ptr<int> aptr;
 
    {
        // create a shared_ptr that owns a Foo and a deleter
        auto foo_p = new Foo;
        std::shared_ptr<Foo> r(foo_p, foo_deleter);
        aptr = std::shared_ptr<int>(r, &r->i); // aliasing ctor
        // aptr is now pointing to an int, but managing the whole Foo
    } // r gets destroyed (deleter not called)
 
    // obtain pointer to the deleter:
    if (auto del_p = std::get_deleter<void(*)(Foo*)>(aptr))
    {
        std::cout << "shared_ptr<int> owns a deleter\n";
        if (*del_p == foo_deleter)
            std::cout << "...and it equals &foo_deleter\n";
    }
    else
        std::cout << "The deleter of shared_ptr<int> is null!\n";
} // deleter called here

輸出

shared_ptr<int> owns a deleter
...and it equals &foo_deleter
foo_deleter called!

另請參閱

(建構函式)	std::shared_ptr 建構函式 (公開成員函式)
get_deleter	返回用於銷燬託管物件的刪除器 (std::unique_ptr<T,Deleter> 的公共成員函式)