【gdb】向上或向下切换函数堆栈帧
向上或向下切换函数堆栈帧
1. 例子:
#include <stdio.h>
int func1(int a)
{
return 2 * a;
}
int func2(int a)
{
int c = 0;
c = 2 * func1(a);
return c;
}
int func3(int a)
{
int c = 0;
c = 2 * func2(a);
return c;
}
int main(void)
{
printf("%d\n", func3(10));
return 0;
}
输出:
用gdb调试程序时,当程序暂停后,可以用“up n
”或“down n
”命令向上或向下选择函数堆栈帧,其中n
是层数。以上面程序为例:
(gdb) b test.c:5
Breakpoint 1 at 0x40053d: file test.c, line 5.
(gdb) r
Starting program: /home/nanxiao/test
Breakpoint 1, func1 (a=10) at test.c:5
5 return 2 * a;
(gdb) bt
#0 func1 (a=10) at test.c:5
#1 0x0000000000400560 in func2 (a=10) at test.c:11
#2 0x0000000000400586 in func3 (a=10) at test.c:18
#3 0x000000000040059e in main () at test.c:24
(gdb) frame 2
#2 0x0000000000400586 in func3 (a=10) at test.c:18
18 c = 2 * func2(a);
(gdb) up 1
#3 0x000000000040059e in main () at test.c:24
24 printf("%d\n", func3(10));
(gdb) down 2
#1 0x0000000000400560 in func2 (a=10) at test.c:11
11 c = 2 * func1(a);
可以看到程序断住后,先执行“frame 2
”命令,切换到fun3
函数。接着执行“up 1
”命令,此时会切换到main
函数,也就是会往外层的堆栈帧移动一层。反之,当执行“down 2
”命令后,又会向内层堆栈帧移动二层。如果不指定n
,则n
默认为1
. 还有“up-silently n
”和“down-silently n
”这两个命令,与“up n
”和“down n
”命令区别在于,切换堆栈帧后,不会打印信息,仍以上面程序为例:
(gdb) up
#2 0x0000000000400586 in func3 (a=10) at test.c:18
18 c = 2 * func2(a);
(gdb) bt
#0 func1 (a=10) at test.c:5
#1 0x0000000000400560 in func2 (a=10) at test.c:11
#2 0x0000000000400586 in func3 (a=10) at test.c:18
#3 0x000000000040059e in main () at test.c:24
(gdb) up-silently
(gdb) i frame
Stack level 3, frame at 0x7fffffffe5a0:
rip = 0x40059e in main (test.c:24); saved rip = 0x7ffff7a35ec5
caller of frame at 0x7fffffffe590
source language c.
Arglist at 0x7fffffffe590, args:
Locals at 0x7fffffffe590, Previous frame's sp is 0x7fffffffe5a0
Saved registers:
rbp at 0x7fffffffe590, rip at 0x7fffffffe598
可以看到从func3
切换到main
函数堆栈帧时,并没有打印出相关信息。
参考资料