如何在C中显示无符号长long的最大值？

Question

我在这做错了什么？

$ cat size.c
#include<stdio.h>
#include<math.h>

int main() {

printf ("sizeof unsigned int = %d bytes.\n", sizeof(unsigned int));
printf ("sizeof unsigned long long = %d bytes.\n", sizeof(unsigned long long));

printf ("max unsigned int = %d\n", (int)(pow(2, 32) - 1));
printf ("max unsigned long long = %lld\n", (unsigned long long)(pow(2, 64) - 1));

}
$ gcc size.c -o size
$ ./size
sizeof unsigned int = 4 bytes.
sizeof unsigned long long = 8 bytes.
max unsigned int = 2147483647
max unsigned long long = -1
$ 

我期待18446744073709551615输出而不是-1最后一行的输出.

---

好吧,我完全错过了我得到的错误值为2 ³² - 1,应该是4294967295,而不是2147483647.事情现在变得更有意义了.

Answer 1

只是不要以为它具有一定的使用价值 ULLONG_MAX

Answer 2

使用%llu,而不是%lld.d是用于有符号整数,因此将其printf显示为带符号的长整数.