即使我使用 malloca 分配了内存，为什么仍然调用析构函数？

Question

#include<iostream>
#include<stdlib.h>

using namespace std;

class Test
{
public:
    Test()
    {
        cout<<"constructor called"<<endl;`
    }

    ~Test()
    {
        cout<<"Destructor called"<<endl;
    }
};

int main()
{
    ///constructor called
    Test *t=new Test();
    free(t);
    Test *t2=(Test*)malloc(sizeof(Test));
    ///destructor getting called
    delete t2;
    getchar();
    return 0;
}

Answer 1

The semantics of delete t2 is to call the destructor and then to free the space.

Here your code has undefined behavior since you cannot use the free function to free the space allocated by new . You can neither use the delete keyword to free the space allocated by malloc .

Answer 2

The code doesn't even compile: malloc return a pointer to the memory that been allocated, so instead of:

Test t2=(Test)malloc(sizeof(Test));

You need to do

Test * t2=(Test*)malloc(sizeof(Test));

malloc is in c and delete is in C++.

After 'malloc'/'calloc' comes 'free'. 'free' only releases memory.

After 'new' comes 'delete'. 'delete' calls the destructor and then releases memory.