使用哪个投射; static_cast或reinterpret_cast？ [英] Which cast to use; static_cast or reinterpret_cast?

问题描述

int i = 1000;
void *p = &i;

int *x = static_cast<int*>(p);
int *y = reinterpret_cast<int*>(p);

这个转换应该用于转换 void * 到 int * 为什么？

which cast should be used to convert from void* to int* and why?

推荐答案

static_cast ，只要你知道（通过你的程序的设计），指向的东西真的是一个 int 。

static_cast provided that you know (by design of your program) that the thing pointed to really is an int.

static_cast旨在逆转任何隐式转换。您转换为 void * 隐含，因此您可以（并应该）转换回 static_cast

static_cast is designed to reverse any implicit conversion. You converted to void* implicitly, therefore you can (and should) convert back with static_cast if you know that you really are just reversing an earlier conversion.

有了这个假设，没有什么被重新解释 - void 是一个不完整的类型，意味着它没有值，所以在任何时候，你解释一个存储的int值void或存储的void value作为int。 void * 只是一个丑陋的说法，我不知道类型，但我要把指针传递给别人谁。

With that assumption, nothing is being reinterpreted - void is an incomplete type, meaning that it has no values, so at no point are you interpreting either a stored int value "as void" or a stored "void value" as int. void* is just an ugly way of saying, "I don't know the type, but I'm going to pass the pointer on to someone else who does".

reinterpret_cast 如果您省略了细节，这意味着您可能实际使用类型以外的类型读取内存

reinterpret_cast if you've omitted details that mean you might actually be reading memory using a type other than the type is was written with, and be aware that your code will have limited portability.

顺便说一句，使用没有很多好的理由， void * 以这种方式在C ++中的指针。 C风格的回调接口通常可以用模板函数（类似于标准函数 qsort ）或虚拟接口（类似于注册监听器的任何东西）替换， 。如果你的C ++代码使用一些C API，当然你没有太多的选择。

By the way, there are not very many good reasons for using a void* pointer in this way in C++. C-style callback interfaces can often be replaced with either a template function (for anything that resembles the standard function qsort) or a virtual interface (for anything that resembles a registered listener). If your C++ code is using some C API then of course you don't have much choice.

这篇关于使用哪个投射; static_cast或reinterpret_cast？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！