delete与析构函数的显式调用 >在C++中调用删除>代码>在分配为新< /COD>的对象中调用类的析构函数，并释放内存。如果不是删除对象，而是显式调用其析构函数，然后释放内存，会有什么区别吗

例如，考虑以下示例

#include <iostream>

struct A {
  int i;
  ~A() { std::cout << "Destructor, i was " << i << std::endl; }
};

int main()
{
  A* p = new A{3};
  p->~A();
  free(p);

  return 0;
}

使用

valgrind

/

memcheck

运行程序时会出现一个不匹配的free/delete错误：

==27743== Memcheck, a memory error detector
==27743== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==27743== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==27743== Command: ./destructor
==27743== 
Destructor, i was 3
==27743== Mismatched free() / delete / delete []
==27743==    at 0x4C3033B: free (vg_replace_malloc.c:530)
==27743==    by 0x4009FC: main (in /tmp/destructor)
==27743==  Address 0x5bbac80 is 0 bytes inside a block of size 4 alloc'd
==27743==    at 0x4C2F77F: operator new(unsigned long) (vg_replace_malloc.c:334)
==27743==    by 0x4009DA: main (in /tmp/destructor)
==27743== 
==27743== 
==27743== HEAP SUMMARY:
==27743==     in use at exit: 0 bytes in 0 blocks
==27743==   total heap usage: 3 allocs, 3 frees, 73,732 bytes allocated
==27743== 
==27743== All heap blocks were freed -- no leaks are possible
==27743== 
==27743== For counts of detected and suppressed errors, rerun with: -v
==27743== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

但是，没有内存泄漏

我当然知道，处理上述代码中对象

p

的标准方法是调用

delete

。 我的问题比较正式：

• delete

  是否完全等同于调用析构函数和

  免费

  ？标准是否规定了这一点，或者我遇到了UB 用上面的代码

---

虽然显式调用析构函数是合法的，但您希望这样做的情况非常罕见（例如，在较大的缓冲区中构造和销毁对象的std:：vector）

---

请注意，您应该始终将分配器与适当的内存释放、malloc/free、new/delete等进行匹配。虽然运算符new（）通常依赖malloc，但并不要求它这样做，在这种情况下，您的不匹配将产生未定义的结果。

将非空指针传递到

free（）如果指针不是由
malloc（）
、
calloc（）
或
realloc（）
返回，则给出未定义的行为。因此，您对
free（）
的调用具有未定义的行为。另外：。@francesco但您的问题也有很多答案。例如，请参阅我以前的评论，其中包含复制粘贴链接。根本无法保证
new
使用
malloc
/
calloc
/
realloc
@DanielLangr，我不认为这是重复的。此问题知道dtor，但要求dtor+
free
vs
delete
。这是不同的…@m8mble如果这个问题在别处得到了回答，尽管另一个问题的提问方式不同，那么它是重复的。尽管我们可能会争论：）。但答案是一样的。顺便说一句，这两个问题都解决了同一个问题。不调用析构函数不一定是个问题；参见，例如。
==27743== Memcheck, a memory error detector
==27743== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==27743== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==27743== Command: ./destructor
==27743== 
Destructor, i was 3
==27743== Mismatched free() / delete / delete []
==27743==    at 0x4C3033B: free (vg_replace_malloc.c:530)
==27743==    by 0x4009FC: main (in /tmp/destructor)
==27743==  Address 0x5bbac80 is 0 bytes inside a block of size 4 alloc'd
==27743==    at 0x4C2F77F: operator new(unsigned long) (vg_replace_malloc.c:334)
==27743==    by 0x4009DA: main (in /tmp/destructor)
==27743== 
==27743== 
==27743== HEAP SUMMARY:
==27743==     in use at exit: 0 bytes in 0 blocks
==27743==   total heap usage: 3 allocs, 3 frees, 73,732 bytes allocated
==27743== 
==27743== All heap blocks were freed -- no leaks are possible
==27743== 
==27743== For counts of detected and suppressed errors, rerun with: -v
==27743== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)