C编程——unsigned int溢出问题

Question

我想打印一个整型变量，值为3000000000；

所以我写了下面的代码然后运行它，但是打印的值不正确。我认为变量溢出了。但是不知道为什么。

#include<stdio.h>

int main(void) {
    unsigned int num1 = 3000000000;

    printf("%d", num1);
}

据我所知，无符号整数类型变量的最大值是(2^32-1 = 4,294,967,296 - 1)当代码符合Win32 API. 但是打印出来的值为-1294967296.

我不知道为什么我的代码会发生溢出。

如果有人知道原因，请告诉我:)

此致，

我使用的是 Microsoft Visual Studio 2015 Professional。

Answer 1

使用 %u 而不是 %d

对于printf：

%d 被以下用户使用：

d, i The int argument is converted to signed decimal notation.The precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros. The default precision is 1. When 0 is printed with an explicit precision 0, the output is empty.

%u 被以下用户使用：

o, u, x, X The unsigned int argument is converted to unsigned octal (o), unsigned decimal (u), or unsigned hexadecimal (x and X) nota‐ tion. The letters abcdef are used for x conversions; the let‐ ters ABCDEF are used for X conversions. The precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros. The default precision is 1. When 0 is printed with an explicit precision 0, the output is empty.

见http://man7.org/linux/man-pages/man3/printf.3.html

C编程——unsigned int溢出问题

C programming - unsigned int overflow problem

c

integer

int

overflow

unsigned