谁能帮我解释一下这段代码的处理过程 [英] Can anyone help me with the explanation of the processing of this snippet of code

问题描述

其实我是用一个在线的c编译器编译的，代码的输出是5...处理是怎么进行的??

Actually i compiled this in a online c compiler, the output of the code was 5... how did the processing take place??

#include <stdio.h>

int main()
{
    struct ab {char a,b;};
    union abcd
    {
        int c;
        struct ab d;
    }k;
    k.d.a=5;
    k.d.b=0;
    printf("%d",k.c);
}

推荐答案

你有一个整数和一个包含 2 个字符的结构之间的联合.

you have an union between an integer and a structure containing 2 chars.

代码正在更改结构的第一个字符.因为联合，它会影响另一个联合成员的第一个字节，也就是整数.

The code is changing the first char of the structure. Because of the union, it affects the first byte of the other union member, which is the integer.

在小端机器上，将整数的第一个字节设置为 5 会使该整数为 5，这就是您在此处看到的内容.

On a little-endian machine, setting the first byte of an integer to 5 makes this integer 5 and that's what you're seeing here.

在大端机器上，您最终会得到一个非常大的值，具体取决于整数的实际大小.

On a big-endian machine you end up with a very big value depending of the actual size of an integer.

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