不用指针类型转换用C [英] Needless pointer-casts in C

问题描述

我得到了这个线程我的回答评论：

I got a comment to my answer on this thread:

http://stackoverflow.com/questions/105477

总之我有code是这样的：

In short I had code like this:

int * somefunc (void)
{
  int * temp = (int*) malloc (sizeof (int));
  temp[0] = 0;
  return temp;
}

我得到了这个评论：

I got this comment:

我只能说，请不要投的
  返回的malloc价值？不是这样
  需要和可以隐藏的错误。

Can I just say, please don't cast the return value of malloc? It is not required and can hide errors.

我同意，中投不中C.要求它在C ++强制性的，所以我通常添加他们万一我有端口C ++中的code一天。

I agree that the cast is not required in C. It is mandatory in C++, so I usually add them just in case I have to port the code in C++ one day.

不过，我不知道怎么蒙上这样可以隐藏错误。任何想法？

However, I wonder how casts like this can hide errors. Any ideas?

好像有两边非常好，有效的参数。感谢张贴，乡亲们。

Seems like there are very good and valid arguments on both sides. Thanks for posting, folks.

推荐答案

看来我装修后一个答案，因为我离开的注释：P

It seems fitting I post an answer, since I left the comment :P

基本上，如果你忘了包括文件stdlib.h 编译器将假定的malloc 返回 INT 。没有铸造，你会得到一个警告。随着铸造你不会。

Basically, if you forget to include stdlib.h the compiler will assume malloc returns an int. Without casting, you will get a warning. With casting you won't.

因此​​，通过铸造你什么也得不到，并运行SUP pressing合法警告的风险。

So by casting you get nothing, and run the risk of suppressing legitimate warnings.

很多写这个，快速谷歌搜索将更加详细的解释。

Much is written about this, a quick google search will turn up more detailed explanations.

据认为，

TYPE * p;
p = (TYPE *)malloc(n*sizeof(TYPE));

使得它很明显当你不小心，因为比方说，你以为 P 是键入不是不分配足够的内存键入，因此，我们应该投malloc的，因为这种方法的优点是覆盖意外燮pressing编译器警告较小的成本。

makes it obvious when you accidentally don't allocate enough memory because say, you thought p was TYPe not TYPE, and thus we should cast malloc because the advantage of this method overrides the smaller cost of accidentally suppressing compiler warnings.

我想指出的两件事情：

1. 您应该写 P =的malloc（sizeof的（* P）* N）; 来始终确保你的malloc空间权金额


2. 用上面的方法，你需要在3个地方的变化，如果你改变 P 的类型：一次报关，一次是在的malloc ，一旦中投。

1. you should write p = malloc(sizeof(*p)*n); to always ensure you malloc the right amount of space
2. with the above approach, you need to make changes in 3 places if you ever change the type of p: once in the declaration, once in the malloc, and once in the cast.

总之，我还是个人认为没有必要为铸造的malloc 的返回值，它肯定不是最好的做法。

In short, I still personally believe there is no need for casting the return value of malloc and it is certainly not best practice.

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