sizeof的结果

[HostOOP]

char *cp;

union {
short s;
char c[2];
} un;

问：
sizeof(cp) = ?
sizeof(un) = ?

为什么？？？？

[lbaby]

sizeof cp=一个指针的长度

sizeof un= max{short, sizeof char *2}//取二者较大者

[yuanhen]

sizeof(cp) = 4（字节）；我们的CPU是32位的（即4个字节）
sizeof(un) = sizeof(short int) 16位(2字节)
32-bit data types, sizes, and ranges

Type Size (bits) Range Sample applications
unsigned char 8 0 <= X <= 255 Small numbers and full PC character set
char 8 -128 <= X <= 127 Very small numbers and ASCII characters
short int 16 -32,768 <= X <= 32,767 Counting, small numbers, loop control
unsigned int 32 0 <= X <= 4,294,967,295 Large numbers and loops
int 32 -2,147,483,648 <= X <= 2,147,483,647 Counting, small numbers, loop control
unsigned long 32 0 <= X <= 4,294,967,295 Astronomical distances
enum 32 -2,147,483,648 <= X <= 2,147,483,647 Ordered sets of values
long 32 -2,147,483,648 <= X <= 2,147,483,647 Large numbers, populations

[liuheliaoshi7879]

第一问，答案是一个字符的长度，第二问是取short ， char两种类型所占长度的最大值，因为第二个变量是一个联合体类型，计算它的长度办法就是取其成员变量中长度最大值。

[yang0008]

up

[chinajiji]

sizeof(cp) == sizeof(char*) = sizeof(void*) == sizeof(int) == 4(vc6.0中)
sizeof(un) == (sizeof(short) > sizeof(c) ? sizeof(short), sizeof(c)) == 2 (vc6.0);

[chinajiji]

sizeof(un)如果考虑位对齐调整,可能等于4

[hiliyun]

要看是什么机器了，我在aix下sizeof(cp)＝＝8，也就是aix下int为64位.
但是如果要用turboc2。0的话sizeof(cp)＝＝2所以这主要是看你的机器是多少位得了：）

[langzi8818]

4和2,
我想可能变量太少,所以没有考虑位对齐