选择函数堆栈帧

#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;
}

技巧

用gdb调试程序时，当程序暂停后，可以用“frame n”命令选择函数堆栈帧，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);

可以看到程序断住后，最内层的函数帧为第0帧。执行frame 2命令后，当前的堆栈帧变成了fun3的函数帧。

也可以用“frame addr”命令选择函数堆栈帧，其中addr是堆栈地址。仍以上面程序为例：

(gdb) frame 2
#2  0x0000000000400586 in func3 (a=10) at test.c:18
18              c = 2 * func2(a);
(gdb) i frame
Stack level 2, frame at 0x7fffffffe590:
 rip = 0x400586 in func3 (test.c:18); saved rip = 0x40059e
 called by frame at 0x7fffffffe5a0, caller of frame at 0x7fffffffe568
 source language c.
 Arglist at 0x7fffffffe580, args: a=10
 Locals at 0x7fffffffe580, Previous frame's sp is 0x7fffffffe590
 Saved registers:
  rbp at 0x7fffffffe580, rip at 0x7fffffffe588
(gdb) frame 0x7fffffffe568
#1  0x0000000000400560 in func2 (a=10) at test.c:11
11              c = 2 * func1(a);

使用“i frame”命令可以知道0x7fffffffe568是func2的函数堆栈帧地址，使用“frame 0x7fffffffe568”可以切换到func2的函数堆栈帧。

参见 gdb手册.