c++ - 构造后调用 delete 抛出异常

Question

我正在阅读 Effective C++ 第 3 版，第 52 条“Write placement delete if you write placement new”。

我想知道如何让operator delete在构造抛出异常后自动调用。

#include <iostream>
using namespace std;

class A {
    int i;
public:
    static void* operator new(std::size_t size) throw(std::bad_alloc) {
        return malloc(size);
    }
    static void operator delete(void* p) throw() {
        cout << "delete" << endl;
        free(p);
    }
    A() {
        throw exception();
    }
};

int main() {
    A* a = new A;
}

以上代码只输出:

terminate called after throwing an instance of 'std::exception'
  what():  std::exception
[1]    28476 abort      ./test_clion

Answer 1

引用:operator delete, operator delete[]

我应该在 try {} 中编写 new。目前对异常知之甚少。

#include <iostream>
using namespace std;

class A {
    int i;
public:
    static void* operator new(std::size_t size) throw(std::bad_alloc) {
        return malloc(size);
    }
    static void operator delete(void* p) throw() {
        cout << "delete" << endl;
        free(p);
    }
    A() {
        throw exception();
    }
};

int main() {
    try {
        A* a = new A;
    } catch (const exception&) {

    }
}

输出:

delete