C ++投射为零

本文介绍了C ++投射为零的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

你好， 以下陈述是合法的（0是实际的 a指针参数，可能是''0'和相关的 演员）？ MyClass * p = reinterpret_cast< MyClass *>（0）; MyClass * p = static_cast< MyClass *>（0）; 谢谢和致以最诚挚的问候， 文杰

Hello, Is the following statements legal (0 is actualy a pointer parameter that could be ''0'' and relevant to the casts) ? MyClass* p = reinterpret_cast<MyClass*>(0); MyClass* p = static_cast<MyClass*>(0); Thanks and best regards, Wenjie

推荐答案

2003年8月17日01:54： 20 -0700， go****@yahoo （文杰）写道： On 17 Aug 2003 01:54:20 -0700, go****@yahoo (Wenjie) wrote: 以下陈述是否合法（0是实际的指针参数，可能是'0''并且与演员相关）？ MyClass * p = reinterpret_cast< MyClass *> ;（0）; MyClass * p = static_cast< MyClass *>（0）; Is the following statements legal (0 is actualya pointer parameter that could be ''0'' and relevantto the casts) ?MyClass* p = reinterpret_cast<MyClass*>(0);MyClass* p = static_cast<MyClass*>(0);

这不是问题。 有什么问题？

That''s not the problem. What is the problem?

Wenjie写道： 你好， 是以下的政治家ts legal（0是实际的一个指针参数，可能是'0''并且与演员相关）？ MyClass * p = reinterpret_cast< MyClass *>（0）; MyClass * p = static_cast< MyClass *>（0）; Hello, Is the following statements legal (0 is actualy a pointer parameter that could be ''0'' and relevant to the casts) ? MyClass* p = reinterpret_cast<MyClass*>(0); MyClass* p = static_cast<MyClass*>(0);

你想做什么？如果你想要一个所谓的NULL指针，那么就忘记 reinterpret_cast。为什么？因为那个是实现定义的。 并且NULL指针实现不一定是具有与包含零的整数相同的实现的指针。关于第二个演员:: 它是不必要的。 0本身将自动转换为NULL指针 的正确类型。 WW aka Attila

What do you want to do? If you want a so-called NULL pointer, then forget the reinterpret_cast. Why? Because that one is implementation defined. And a NULL pointers implementation is not necessarily a pointer having the same implementation as an integer containing zero. About the second cast:: it is unecessary. The 0 itself will automagically convert to a NULL pointer of the right type. WW aka Attila

Wenjie写道： Wenjie wrote: 你好， 以下陈述合法 是的，虽然结果第一个是实现定义。 （0实际上是一个指针参数，可能是'0''并且与演员相关）？ 我不明白。 MyClass * p = reinterpret_cast< MyClass *>（0）; 如果你想要一个空指针，请注意上面并不一定是导致一个。它_might_导致一个所有位为零的指针，并且 指针_might_是一个空指针，但是不能保证。 MyClass * p = static_cast< MyClass *>（0）; Hello, Is the following statements legal Yes, though the result of the first is implementation defined. (0 is actualy a pointer parameter that could be ''0'' and relevant to the casts) ? I don''t understand that. MyClass* p = reinterpret_cast<MyClass*>(0); If you wanted a null pointer, note that the above doesn''t necessarily lead to one. It _might_ lead to a pointer with all bits zero, and that pointer _might_ be a null pointer, but that''s not guaranteed. MyClass* p = static_cast<MyClass*>(0);

这与以下相同： MyClass * p = 0; 使得pa空指针。

This is the same as: MyClass* p = 0; which makes p a null pointer.