C++ 内存泄漏检查中的 Valgrind 错误

Question

我试图弄清楚 Valgrind 的用法，所以我做了一个简单的程序，但是当我在课堂上进行动态内存分配时，Valgrind 似乎给出了一个奇怪的错误。

我的程序是：

class Valgrind_testclass
{
 Valgrind_testclass *Obj;
public:
  Valgrind_testclass() { 
    // Obj = new Valgrind_testclass();  // Test point #3
  }
  ~Valgrind_testclass() {
    //delete Obj;               // Test point #4
  }
};

int main()
{
 Valgrind_testclass valObj;
 // Valgrind_testclass * valObjPtr = new Valgrind_testclass();  // Test point #1
 //delete valObjPtr;                 // Test point #2
 return 0;
}

通过注释掉的测试点，Valgrind 给了我以下信息：

==5273== HEAP SUMMARY:
==5273==     in use at exit: 0 bytes in 0 blocks
==5273==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated

我想这是预期的结果。

现在，当我取消注释测试点 #1 时：

==5288== HEAP SUMMARY:
==5288==     in use at exit: 4 bytes in 1 blocks
==5288==   total heap usage: 1 allocs, 0 frees, 4 bytes allocated
==5288== 
==5288== Searching for pointers to 1 not-freed blocks
==5288== Checked 102,116 bytes
==5288== 
==5288== 4 bytes in 1 blocks are definitely lost in loss record 1 of 1

这又是正确的结果，因为我没有执行删除操作。

在未注释测试点 #2 的情况下，我得到：

==5300== HEAP SUMMARY:
==5300==     in use at exit: 0 bytes in 0 blocks
==5300==   total heap usage: 1 allocs, 1 frees, 4 bytes allocated
==5300== 
==5300== All heap blocks were freed -- no leaks are possible

又是正确的结果。

现在我取消注释测试点 #3，我希望 Valgrind 能够检测到内存泄漏。这是我得到的：

==5313== Process terminating with default action of signal 11 (SIGSEGV)
==5313==  Access not within mapped region at address 0xBE17AFE4
==5313==    at 0x40263A0: operator new(unsigned int) (vg_replace_malloc.c:255)
==5313==  If you believe this happened as a result of a stack
==5313==  overflow in your program's main thread (unlikely but
==5313==  possible), you can try to increase the size of the
==5313==  main thread stack using the --main-stacksize= flag.
==5313==  The main thread stack size used in this run was 8388608.
==5313== Stack overflow in thread 1: can't grow stack to 0xbe17afe0
==5313== 
==5313== Process terminating with default action of signal 11 (SIGSEGV)
==5313==  Access not within mapped region at address 0xBE17AFE0
==5313==    at 0x402040C: _vgnU_freeres (vg_preloaded.c:58)
==5313==  If you believe this happened as a result of a stack
==5313==  overflow in your program's main thread (unlikely but
==5313==  possible), you can try to increase the size of the
==5313==  main thread stack using the --main-stacksize= flag.
==5313==  The main thread stack size used in this run was 8388608.
==5313== 
==5313== HEAP SUMMARY:
==5313==     in use at exit: 1,047,576 bytes in 261,894 blocks
==5313==   total heap usage: 261,894 allocs, 0 frees, 1,047,576 bytes allocated
==5313== 
==5313== Searching for pointers to 261,894 not-freed blocks
==5313== Checked 5,339,952 bytes
==5313== 
==5313== LEAK SUMMARY:
==5313==    definitely lost: 0 bytes in 0 blocks
==5313==    indirectly lost: 0 bytes in 0 blocks
==5313==      possibly lost: 0 bytes in 0 blocks
==5313==    still reachable: 1,047,576 bytes in 261,894 blocks
==5313==         suppressed: 0 bytes in 0 blocks
==5313== Reachable blocks (those to which a pointer was found) are not shown.
==5313== To see them, rerun with: --leak-check=full --show-reachable=yes
==5313== 
==5313== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 17 from 6)

我不确定为什么在这里没有看到类似的内存泄漏错误。 有人可以帮助理解这种情况，无论我做错了什么。 我使用的 Valgrind 命令是：

valgrind -v --tool=memcheck --leak-check=full --num-callers=40  ./ValgrindOutput 

谢谢。

Answer 1

这是因为你有无限递归

Valgrind_testclass 是新的一个 Valgrind_testclass 这是新的另一个 Valgrind_testclass ...无限

Answer 2

程序没有正常结束。您正在查看的是堆栈溢出错误。

构造函数执行new Valgrind_testclass()，它调用构造函数。无限递归！