关于联合体的一道笔试题

ljl_lucifer

回复 30# lwrsmy


    我机器运行出来的266是小端的结果？

linccn

回复 27# melodyzm
是的，在solaris SPACK上的结果是 167837696
在cygwin上的结果是266
在ubuntu8.04上是266

wangzhen11aaa

Reading symbols from /home/wangzhen/c/union...done.
(gdb) l
2        *
3       */
4       #include<stdio.h>
5       union{
6               int i;
7               char a[2];
8       }x;
9       int main()
10      {
11              x.a[0] = 10;
(gdb) b 5
Breakpoint 1 at 0x80483b5: file union.c, line 5.
(gdb) run
Starting program: /home/wangzhen/c/union

Breakpoint 1, main () at union.c:11
11              x.a[0] = 10;
(gdb) display &x
1: &x = (union {...} *) 0x804963c
(gdb) display &x.i
2: &x.i = (int *) 0x804963c
(gdb) display &x.a
3: &x.a = (char (*)[2]) 0x804963c
(gdb) display &x.a[1]
4: &x.a[1] = 0x804963d ""
(gdb) display &x.a[0]
5: &x.a[0] = 0x804963c ""
(gdb) s
12              x.a[1] = 1;
5: &x.a[0] = 0x804963c "\n"
4: &x.a[1] = 0x804963d ""
3: &x.a = (char (*)[2]) 0x804963c
2: &x.i = (int *) 0x804963c
1: &x = (union {...} *) 0x804963c
(gdb) display x.a[0]
6: x.a[0] = 10 '\n'
(gdb) display x.a[1]
7: x.a[1] = 0 '\000'
(gdb) s
13              printf("%d\n",x.i);
7: x.a[1] = 1 '\001'
6: x.a[0] = 10 '\n'
5: &x.a[0] = 0x804963c "\n\001"
4: &x.a[1] = 0x804963d "\001"
3: &x.a = (char (*)[2]) 0x804963c
2: &x.i = (int *) 0x804963c
1: &x = (union {...} *) 0x804963c
(gdb) display x
8: x = {i = 266, a = "\n\001"}
(gdb) display a[2]
No symbol "a" in current context.
(gdb) display x.a[2]
9: x.a[2] = 0 '\000'
(gdb) display x.a[3]
10: x.a[3] = 0 '\000'
(gdb) display x.i
11: x.i = 266
(gdb) display x.i
12: x.i = 266
(gdb) display &x.a[3]
13: &x.a[3] = 0x804963f ""
(gdb) display &x.a[2]
14: &x.a[2] = 0x804963e ""
(gdb) display &x.a[2]
14: &x.a[2] = 0x804963e ""
(gdb) display x.a[2]
15: x.a[2] = 0 '\000'
(gdb) display x.a[3]
16: x.a[3] = 0 '\000'


7: x.a[1] = 1 '\001'
6: x.a[0] = 10 '\n'

按照小端来算：(看地址内的内容
应该是0x10a

2768637066

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