【gdb】设置观察点

设置观察点

1. 例子：

#include <stdio.h>
#include <pthread.h>

typedef struct
{
  int a;
  int b;
  int c;
  int d;
  pthread_mutex_t mutex;
} ex_st;

int main(void)
{
  ex_st st = {1, 2, 3, 4, PTHREAD_MUTEX_INITIALIZER};
  printf("%d,%d,%d,%d\n", st.a, st.b, st.c, st.d);
  return 0;
}

默认情况下，gdb以一种“紧凑”的方式打印结构体。以上面代码为例：

(gdb) n
16	  printf("%d,%d,%d,%d\n", st.a, st.b, st.c, st.d);
(gdb) p st
$1 = {a = 1, b = 2, c = 3, d = 4, mutex = {__data = {__lock = 0, __count = 0, __owner = 0, __nusers = 0, __kind = 0, __spins = 0, __elision = 0, 
      __list = {__prev = 0x0, __next = 0x0}}, __size = '\000' <repeats 39 times>, __align = 0}}

可以看到结构体的显示很混乱，尤其是结构体里还嵌套着其它结构体时。可以执行“set print pretty on”命令，这样每行只会显示结构体的一名成员，而且还会根据成员的定义层次进行缩进：

(gdb) set print pretty on
(gdb) p st
$2 = {
  a = 1, 
  b = 2, 
  c = 3, 
  d = 4, 
  mutex = {
    __data = {
      __lock = 0, 
      __count = 0, 
      __owner = 0, 
      __nusers = 0, 
      __kind = 0, 
      __spins = 0, 
      __elision = 0, 
      __list = {
        __prev = 0x0, 
        __next = 0x0
      }
    }, 
    __size = '\000' <repeats 39 times>, 
    __align = 0
  }
}