union学习

union student {int age;int height;}; 

union中的多个成员公用一个最大成员的内存空间，假设int类型占用4个字节的内存空间，那么

union student s;

只会为s分配4个字节的内存

 

下面是union更多的测试：

localhost test # cat main.c #include<stdio.h>union student {int age;int height;};void main(void) {printf("main E./n");union student s1;s1.age = 26;s1.height = 179;printf("s1, age is:%d, height is:%d/n", s1.age, s1.height);s1.height = 179;s1.age = 26;printf("s1, age is:%d, height is:%d/n", s1.age, s1.height);union person {union student s;int weight;};union person p1;p1.s.age = 26;p1.s.height = 179;p1.weight = 136;printf("p1, age is:%d, height is:%d, weight is:%d/n", p1.s.age, p1.s.height, p1.weight);struct teacher {int age;int height;};union man {struct teacher t;int weight;};union man m1;m1.t.age = 38;m1.t.height = 180;m1.weight = 150;printf("m1, age is:%d, height is:%d, weight is:%d/n", m1.t.age, m1.t.height, m1.weight);}localhost test # gcc *.c -o mainlocalhost test # ./main main E.s1, age is:179, height is:179s1, age is:26, height is:26p1, age is:136, height is:136, weight is:136m1, age is:150, height is:180, weight is:150