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UINT_MAX与C中的ULONG_MAX相同

[英]UINT_MAX the same as ULONG_MAX in C

原文 2012-03-17 12:19:01 3 3 c/ max/ long-integer/ unsigned/ kr-c

While solving exercises from the K&R C book, I stumbled upon the exercise 2.1. 在解决K＆R C书中的练习时，我偶然发现了练习2.1。

At first I got as UINT_MAX as -1 , but then I used the %u placeholder, but now its giving me the same number as ULONG_MAX . 起初，我将UINT_MAX为-1 ，但是后来我使用了%u占位符，但是现在它给了我与ULONG_MAX相同的数字。

In the book in Appendix B, they say that UINT_MAX should be 65535 and ULONG_MAX should be 4294967295 , but when running the exercise, its giving me for both UINT_MAX and ULONG_MAX as 4294967295 . 在附录B的书中，他们说UINT_MAX应该为65535 ， ULONG_MAX应该为4294967295 ，但是运行该练习时，它给我的UINT_MAX和ULONG_MAX都UINT_MAX为4294967295 。

Why is that? 这是为什么？

3 个解决方案

First of all, the right way to print an unsigned long is not %u but %lu . 首先，打印unsigned long的正确方法不是%u而是%lu 。 Second, the standard says the minimum value of UINT_MAX is 65535. It can be (and usually is) larger. 其次，标准说UINT_MAX 的最小值是65535。它可以（通常是）更大。

5.2.4.2.1 Sizes of integer types 5.2.4.2.1整数类型的大小

Their implementation-deﬁned values shall be equal or greater in magnitude (absolute value) to those shown, with the same sign. 其实现定义的值的大小（绝对值）应等于或大于所示的相同符号。

On 32-bit platforms, int and long are usually the same, and so their max are also the same. 在32位平台上， int和long通常是相同的，因此它们的最大值也相同。 The same for their unsigned counterparts of course. 当然，对于未签名的同行也是如此。

The appendix is wrong. 附录是错误的。 The only guarantee is that sizeof(long) >= sizeof(int) >= sizeof(char) note the possibility of equality. 唯一的保证是sizeof（long）> = sizeof（int）> = sizeof（char）注意相等的可能性。