winter_course_Question_gdb_test1

xu6wu6gj@kmtath:~/2016-winter-course/test1$ gdb swap
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Reading symbols from swap...done.
(gdb) l
126	
127	
128	
129	return head;
130	
131	
132	
133	}
134	
135	int main(){return 0;}
(gdb) b 135
Breakpoint 1 at 0x40072a: file swap.c, line 135.
(gdb) r
Starting program: /home/xu6wu6gj/2016-winter-course/test1/swap 

Breakpoint 1, main () at swap.c:135
135	int main(){return 0;}
(gdb) p $head = (List)malloc(sizeof(List))
Invalid cast.
(gdb) p $head = (List*)malloc(sizeof(List))
$1 = (List *) 0x602030
(gdb) p $head->value = 1
$2 = 1
(gdb) p $head->next = (List*)malloc(sizeof(List))
$3 = (struct List_node *) 0x602050
(gdb) p $head->next->value = 2
$4 = 2
(gdb) p $head->next->next = (List*)malloc(sizeof(List))
$5 = (struct List_node *) 0x602070
(gdb) p $head->next->next->value = 3
$6 = 3
(gdb) p $head->next->next->next = (List*)0
$7 = (struct List_node *) 0x0

/*
以上三行(gdb) p xxxx  開頭是用來製造linked list用的  依序是 1 2 3總共3個node  1 是head 
(從這邊就可以看出 如果要測比較大的list 這是個笨方法)
*/

(gdb) p $head = swap($head,$head->next,$head->next->next)
$8 = (List *) 0x602030

/*
交換第二個和第三個node  預期應該是 1  3  2
*/

(gdb) p $head->value
$9 = 1
(gdb) p $head->next->value
$10 = 3
(gdb) p $head->next->next->value
$11 = 2

/*
果然是XD 再來繼續測別的
*/

(gdb) p $head->next->next->next
$12 = (struct List_node *) 0x0
(gdb) p $head = swap($head,$head->next,$head->next->next)
$13 = (List *) 0x602030

/*
一樣二換三  應該是 1  2  3
*/

(gdb) p $head->value
$14 = 1
(gdb) p $head->next->value
$15 = 2
(gdb) p $head->next->next->value
$16 = 3
(gdb) p $head->next->next->next
$17 = (struct List_node *) 0x0

/*
果然  
*/

(gdb) p $head->next->next->next = (List*)malloc(sizeof(List))
$18 = (struct List_node *) 0x602090
(gdb) p $head->next->next->next->value = 4
$19 = 4
(gdb) p $head->next->next->next->next = (List*)0
$20 = (struct List_node *) 0x0
(gdb) p $head = swap($head,$head->next,$head->next->next->next)
$21 = (List *) 0x602030
(gdb) p $head->value
$22 = 1
(gdb) p $head->next->value
$23 = 4
(gdb) p $head->next->next->value
$24 = 3
(gdb) p $head->next->next->next->value
$25 = 2
(gdb) p $head->next->next->next->next
$26 = (struct List_node *) 0x0
(gdb) p $head = swap($head,$head->next,$head->next->next->next)
$27 = (List *) 0x602030
(gdb) p $head->value
$28 = 1
(gdb) p $head->next->value
$29 = 2
(gdb) p $head->next->next->value
$30 = 3
(gdb) p $head->next->next->next->value
$31 = 4
(gdb) p $head->next->next->next->next
$32 = (struct List_node *) 0x0
(gdb) p $head = swap($head,$head,$head->next->next)
$33 = (List *) 0x602070
(gdb) p $head->value
$34 = 3
(gdb) p $head->next->value
$35 = 2
(gdb) p $head->next->next->value
$36 = 1
(gdb) p $head->next->next->next->value
$37 = 4
(gdb) p $head->next->next->next->next
$38 = (struct List_node *) 0x0
(gdb) p $head = swap($head,$head,$head->next->next)
$39 = (List *) 0x602030
(gdb) p $head->value
$40 = 1
(gdb) p $head->next->value
$41 = 2
(gdb) p $head->next->next->value
$42 = 3
(gdb) p $head->next->next->next->value
$43 = 4
(gdb) p $head->next->next->next->next
$44 = (struct List_node *) 0x0
(gdb) p $head->next->next->next->next->value
Cannot access memory at address 0x0