内存泄漏会发生什么？

Question

我真的不明白发生异常时堆中分配的内存会发生什么：

#include <iostream>
#include <vector>
using namespace std;

class Base {
private:
    int *a;
public:
    Base() {
        // a = new int[100];

        throw runtime_error("err");
    }

    ~Base() {
        // delete[] a;
    }
};

int main() {
    std::vector<Base> bases;
    Base base;
    bases.push_back(base);

    std::cout << bases.size() << std::endl;

    return 0;
}

好的，现在，它只是抛出异常的空程序。下一个程序，在堆中分配内存：

#include <iostream>
#include <vector>
using namespace std;

class Base {
private:
    int *a;
public:
    Base() {
        a = new int[100];

        throw runtime_error("err");
    }

    ~Base() {
        // delete[] a;
    }
};

int main() {
    std::vector<Base> bases;
    Base base;
    bases.push_back(base);

    std::cout << bases.size() << std::endl;

    return 0;
}

计划1：

==14151== HEAP SUMMARY:
==14151==     in use at exit: 72,876 bytes in 3 blocks
==14151==   total heap usage: 4 allocs, 1 frees, 72,908 bytes allocated
==14151== 
==14151== Searching for pointers to 3 not-freed blocks
==14151== Checked 116,088 bytes
==14151== 
==14151== 144 bytes in 1 blocks are possibly lost in loss record 2 of 3
==14151==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==14151==    by 0x4EC641F: __cxa_allocate_exception (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21)
==14151==    by 0x400F44: Base::Base() (in /home/twite/CLionProjects/oop_learn/driver1)
==14151==    by 0x400E25: main (in /home/twite/CLionProjects/oop_learn/driver1)
==14151== 
==14151== LEAK SUMMARY:
==14151==    definitely lost: 0 bytes in 0 blocks
==14151==    indirectly lost: 0 bytes in 0 blocks
==14151==      possibly lost: 144 bytes in 1 blocks
==14151==    still reachable: 72,732 bytes in 2 blocks

计划2：

==14171== HEAP SUMMARY:
==14171==     in use at exit: 73,276 bytes in 4 blocks
==14171==   total heap usage: 5 allocs, 1 frees, 73,308 bytes allocated
==14171== 
==14171== Searching for pointers to 4 not-freed blocks
==14171== Checked 116,096 bytes
==14171== 
==14171== 144 bytes in 1 blocks are possibly lost in loss record 2 of 4
==14171==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==14171==    by 0x4EC641F: __cxa_allocate_exception (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21)
==14171==    by 0x400F98: Base::Base() (in /home/twite/CLionProjects/oop_learn/driver2)
==14171==    by 0x400E65: main (in /home/twite/CLionProjects/oop_learn/driver2)
==14171== 
==14171== LEAK SUMMARY:
==14171==    definitely lost: 0 bytes in 0 blocks
==14171==    indirectly lost: 0 bytes in 0 blocks
==14171==      possibly lost: 144 bytes in 1 blocks
==14171==    still reachable: 73,132 bytes in 3 blocks

那么，内存泄漏在哪里？ Valgrind并没有告诉我有关内存泄漏的信息，但是我看到了第二个程序。

Answer 1

当程序终止时，操作系统会清除它分配的任何内存 - 通常不是问题。关机时的内存泄漏很少成为问题（除非一些非常重要的析构函数没有机会运行）。内存泄漏是一个真正的问题，当它们在运行时发生并导致程序内存使用无限增长（最终导致资源耗尽）。