Question

我正在学习创建指针数组并释放内存。这是我的简单代码

#include <iostream>

using namespace std;

int main()
{
  int* classroom[5];
  for (int i = 0; i < 5; i++) {
    classroom[i] = new int;
  }
  for (int i = 0; i < 5; i++) {
    classroom[i] = &i;
    cout<<*classroom[i]<<endl;
  }
  for (int i = 0; i < 5; i++) {
    delete classroom[i];
  }
  return 0;
}

当我在valgrind中运行以检查内存泄漏时，结果是

==2868== Memcheck, a memory error detector
==2868== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==2868== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==2868== Command: ./m
==2868== 
0
1
2
3
4
==2868== Invalid free() / delete / delete[] / realloc()
==2868==    at 0x402ACFC: operator delete(void*) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==2868==    by 0x8048700: main (in /home/student/Downloads/demo/m)
==2868==  Address 0xbea69244 is on thread 1's stack
==2868== 
==2868== 
==2868== HEAP SUMMARY:
==2868==     in use at exit: 20 bytes in 5 blocks
==2868==   total heap usage: 5 allocs, 5 frees, 20 bytes allocated
==2868== 
==2868== LEAK SUMMARY:
==2868==    definitely lost: 20 bytes in 5 blocks
==2868==    indirectly lost: 0 bytes in 0 blocks
==2868==      possibly lost: 0 bytes in 0 blocks
==2868==    still reachable: 0 bytes in 0 blocks
==2868==         suppressed: 0 bytes in 0 blocks
==2868== Rerun with --leak-check=full to see details of leaked memory
==2868== 
==2868== For counts of detected and suppressed errors, rerun with: -v
==2868== ERROR SUMMARY: 5 errors from 1 contexts (suppressed: 0 from 0)

我的问题是，为什么我收到了消息＆＃34;无效的免费（）/删除/删除[] / realloc []＆＃34; ？以及如何解决它？

谢谢，

Answer 1

在这个循环中

for (int i = 0; i < 5; i++) {
    classroom[i] = &i;
    cout<<*classroom[i]<<endl;
}

你正在摧毁阵列的内存。您将所有指针设置为i的地址，然后当for循环结束时i被销毁，您现在有悬空指针。试图删除它们是未定义的行为。

Answer 2

classroom[i] = &i;

应该是：

*classroom[i] = i;

您将使用new分配的指针替换为局部变量i的地址。然后，您稍后尝试删除该指针，但您不能删除局部变量，只能删除使用new分配的变量。您实际想要做的是将i的值复制到动态分配的变量中。

Answer 3

我认为问题在于，当您delete每个classroom时，它不再指向由int创建的new的原始记忆位置，因为您是没有将i的值推到classroom[i]的内存位置，实际上您正在将classroom[i]更改为指向i的内存位置。

尝试更改

classroom[i] = &i;

到

*(classroom[i]) = i;

无效的delete []指针数组

3 个答案: