将使用删除与基类指针导致内存泄漏？ [英] Will using delete with a base class pointer cause a memory leak?

问题描述

给定两个类只有原始数据类型，没有自定义析构函数/释放器。
C ++规范是否保证它将按正确的大小释放？

  struct A {int foo; }; 
 struct B：public A {int bar [100000]; }; 
 A * a =（A *）new B; 
 delete a; 
  

我想知道我需要写一个空的虚拟 dtor？

我试过g ++和vc ++ 2008，他们不会导致泄漏。但是我想知道C ++标准是什么。

解决方案

除非基类析构函数是虚函数，否则是未定义的行为。参见5.3.5 / 4：

如果操作数[的删除操作符]的静态类型与其动态类型不同，静态类型应该是操作数动态类型的基类，静态类型应该有一个虚拟析构函数或行为是未定义的。

Given two classes have only primitive data type and no custom destructor/deallocator. Does C++ spec guarantee it will deallocate with correct size?

struct A { int foo; };
struct B: public A { int bar[100000]; };
A *a = (A*)new B;
delete a;

I want to know do I need to write an empty virtual dtor?

I have tried g++ and vc++2008 and they won't cause a leak. But I would like to know what is correct in C++ standard.

解决方案

Unless the base class destructor is virtual, it's undefined behaviour. See 5.3.5/4:

If the static type of the operand [of the delete operator] is different from its dynamic type, the static type shall be a base class of the operand's dynamic type and the static type shall have a virtual destructor or the behaviour is undefined.

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