删除指针时出现段错误 [英] Segfault when deleting pointer

问题描述

运行某些C ++代码时，我一直遇到段错误.我已将问题隔离到程序中删除指针的一行.这是一个产生相同错误的简单示例:

I've been experiencing segfaults when running some C++ code. I've isolated the problem to a line in the program that deletes a pointer. Here's a simple example that produces the same error:

int main()
{
  int* pointer=0;
  int number = 3;

  pointer = &number;
  delete pointer;//This line causes a segmentation fault
  pointer=0;

  return 0;
}

稍作修改就会产生可以正常工作的代码:

A slight modification produces code that will work as expected:

int main()
{
  int* pointer=new int(3);

  delete pointer;//This line now works
  pointer=0;

  return 0;
}

有人可以解释为什么第一个引起段错误而第二个不引起段错误吗?我知道指针不是无效的，因为它已分配给数字变量的地址.

Can someone explain why the first causes a segfault and the second does not? I know the pointer isn't invalid, since it's been assigned to the address of the number variable.

推荐答案

您应该只使用new分配的delete内存.在堆栈上声明的自动变量不需要delete d.通常，请始终匹配您的内存分配和释放类型:

You should only ever delete memory that has been allocated with new. Automatic variables declared on the stack do not need to be deleted. As a rule, always match your memory allocation and deallocation types:

• 用new分配的内存应该用delete释放.
• 用new []分配的内存应该用delete []释放.
• 用malloc()分配的内存应该用free()释放.

• Memory allocated with new should be deallocated with delete.
• Memory allocated with new [] should be deallocated with delete [].
• Memory allocated with malloc() should be deallocated with free().

segfault是因为delete运算符将尝试将该内存放回堆中，并且该操作依赖于某些内存属性，这些属性对于不是由其产生的堆栈上的自动内存不成立堆.

The segfault is because the delete operator will attempt to put that memory back into the heap, and that relies on certain properties of the memory that don't hold true for automatic memory on the stack that didn't originate from the heap.

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