将使得普通int 64位打破了很多合理的code的？ [英] Would making plain int 64-bit break a lot of reasonable code?

问题描述

直到最近，我会考虑大多数系统实现者/供应商的决定，以保持纯 INT 32位甚至64位的机器某种权宜之计疣。随着现代C99固定大小的类型（ int32_t 和 uint32_t的等）需要那里是一个标准的整数每个大小为8，16，32和64型大多消失，好像 INT 也可以同样进行64位。

Until recently, I'd considered the decision by most systems implementors/vendors to keep plain int 32-bit even on 64-bit machines a sort of expedient wart. With modern C99 fixed-size types (int32_t and uint32_t, etc.) the need for there to be a standard integer type of each size 8, 16, 32, and 64 mostly disappears, and it seems like int could just as well be made 64-bit.

不过，平原 INT 规模最大的实际后果用C来自一个事实，即Ç基本上不会对算术更小的超 - INT 类型。特别是，如果 INT 大于32位，在 uint32_t的值的算术结果已键入<$大C $ C>符号int ，这是相当令人不安。

However, the biggest real consequence of the size of plain int in C comes from the fact that C essentially does not have arithmetic on smaller-than-int types. In particular, if int is larger than 32-bit, the result of any arithmetic on uint32_t values has type signed int, which is rather unsettling.

这是一个很好的理由让 INT 永久固定在32位对现实世界的实现？我倾向于说是的。在我看来，像有可能是一个巨大的类的用途uint32_t的该休息的时候 INT 大于32位。即使在应用一元减或按位补运算符，除非你投回到 uint32_t的变得危险。

Is this a good reason to keep int permanently fixed at 32-bit on real-world implementations? I'm leaning towards saying yes. It seems to me like there could be a huge class of uses of uint32_t which break when int is larger than 32 bits. Even applying the unary minus or bitwise complement operator becomes dangerous unless you cast back to uint32_t.

当然，同样的问题也适用于 uint16_t 和 uint8_t有当前实现，但每个人似乎都知道并用于把它们当作小于- - INT 。类型

Of course the same issues apply to uint16_t and uint8_t on current implementations, but everyone seems to be aware of and used to treating them as "smaller-than-int" types.

推荐答案

正如你所说，我认为促销规则真的是凶手。 uint32_t的然后将提升到 INT 键，突然间你已签署的算术几乎人人都预期未签名。

As you say, I think that the promotion rules really are the killer. uint32_t would then promote to int and all of a sudden you'd have signed arithmetic where almost everybody expects unsigned.

这将大多隐匿在你做的只是算术和分配回一个 uint32_t的的地方。但它可能是在你做对比常量的地方是致命的。无论code，它依赖于这样的比较没有做明确的投是合理的，我不知道。铸造像常数（uint32_t的）1 可能会变得非常乏味。我个人至少总是用后缀 U 对，我想是无符号常量，但是这已经是不为可读，因为我想。

This would be mostly hidden in places where you do just arithmetic and assign back to an uint32_t. But it could be deadly in places where you do comparison to constants. Whether code that relies on such comparisons without doing an explicit cast is reasonable, I don't know. Casting constants like (uint32_t)1 can become quite tedious. I personally at least always use the suffix U for constants that I want to be unsigned, but this already is not as readable as I would like.

也有记住， uint32_t的等不能保证存在。甚至没有 uint8_t有。的，执法是POSIX的延伸。因此，在这个意义上说C作为一门语言是远远不能做出这一举动。

Also have in mind that uint32_t etc are not guaranteed to exist. Not even uint8_t. The enforcement of that is an extension from POSIX. So in that sense C as a language is far from being able to make that move.

这篇关于将使得普通int 64位打破了很多合理的code的？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！