我们知道，int的大小在大多数计算机里面存储长度是4个字节

如果，最高位被符号位占领，那么他的取值区间就是

- $2^{31}$ ~ $2^{31}$ -1

我们可以用一小段代码来计算这个长度

#include <stdio.h>
#include <stdint.h>
#include <wchar.h>
 
int main(void)
{
    printf("PTRDIFF_MIN    = %td\n", PTRDIFF_MIN);
    printf("PTRDIFF_MAX    = %+td\n", PTRDIFF_MAX);
    printf("SIZE_MAX       = %zu\n", SIZE_MAX);
    printf("SIG_ATOMIC_MIN = %+jd\n",(intmax_t)SIG_ATOMIC_MIN);
    printf("SIG_ATOMIC_MAX = %+jd\n",(intmax_t)SIG_ATOMIC_MAX);
    printf("WCHAR_MIN      = %+jd\n",(intmax_t)WCHAR_MIN);
    printf("WCHAR_MAX      = %+jd\n",(intmax_t)WCHAR_MAX);
    printf("WINT_MIN       = %jd\n", (intmax_t)WINT_MIN);
    printf("WINT_MAX       = %jd\n", (intmax_t)WINT_MAX);
    printf("[-%lld]-[+%lld]\n",1ll << (sizeof(int)*8 -1) ,(1ll << (sizeof(int)*8 -1)) -1 );
}

weiqifa@ubuntu:~/c/sizeof$ gcc sizeof.c && a.out
PTRDIFF_MIN = -9223372036854775808
PTRDIFF_MAX = +9223372036854775807
SIZE_MAX = 18446744073709551615
SIG_ATOMIC_MIN = -2147483648
SIG_ATOMIC_MAX = +2147483647
WCHAR_MIN = -2147483648
WCHAR_MAX = +2147483647
WINT_MIN = 0
WINT_MAX = 4294967295
[-2147483648]-[+2147483647]
weiqifa@ubuntu:~/c/sizeof$

里面提到的WCHARMIN WCHAR_MAX 关于他们的介绍如下

Numeric limits - cppreference.com

这个文件的位置在 /usr/include/limits.h

截图看看里面的内容