用linux编程时，我们不时会遇到Segmentation fault，其实这就是段错误。引发段错误通常是数组越界，出现野指针，在一些作业网上可能也会显示runtime error，遇到这种情况我们该怎么办？难道一行一行看代码？
显然要调试程序。这里我用的是gdb。
apple@ubuntu:~/Desktop$ gdb
GNU gdb (Ubuntu 7.9-1ubuntu1) 7.9
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(gdb) file a.out
Reading symbols from a.out...done.
(gdb) run
Starting program: /home/apple/Desktop/a.out
2
648 822
7
Program received signal SIGSEGV, Segmentation fault.
0x00000000004007ec in pop (top=0x7fffffffdf10) at stack.h:27
27 if (p1->next == NULL || p1 == NULL) {
(gdb) p p1->next
Cannot access memory at address 0x8
(gdb) p p1
$1 = (Node *) 0x0
(gdb) quit
A debugging session is active.
Inferior 1 [process 11453] will be killed.
Quit anyway? (y or n) y
调用gdb后输入 file a.out，然后再输入run，就能发现段错误所在位置，然后通过“p 变量”指令，查询所在位置变量的值的情况。然后根据情况判断是哪个部分导致了段错误。