调试已经运行的进程

例子

#include <stdio.h>
#include <pthread.h>
void *thread_func(void *p_arg)
{
        while (1)
        {
                printf("%s\n", (char*)p_arg);
                sleep(10);
        }
}
int main(void)
{
        pthread_t t1, t2;

        pthread_create(&t1, NULL, thread_func, "Thread 1");
        pthread_create(&t2, NULL, thread_func, "Thread 2");

        sleep(1000);
        return;
}

技巧

调试已经运行的进程有两种方法：一种是gdb启动时，指定进程的ID：gdb program processID（也可以用-p或者--pid指定进程ID，例如：gdb program -p=10210）。以上面代码为例，用“ps”命令已经获得进程ID为10210：

bash-3.2# gdb -q a 10210
Reading symbols from /data/nan/a...done.
Attaching to program `/data/nan/a', process 10210
[New process 10210]
Retry #1:
Retry #2:
Retry #3:
Retry #4:
Reading symbols from /usr/lib/libc.so.1...(no debugging symbols found)...done.
[Thread debugging using libthread_db enabled]
[New LWP    3        ]
[New LWP    2        ]
[New Thread 1 (LWP 1)]
[New Thread 2 (LWP 2)]
[New Thread 3 (LWP 3)]
Loaded symbols for /usr/lib/libc.so.1
Reading symbols from /lib/ld.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/ld.so.1
[Switching to Thread 1 (LWP 1)]
0xfeeeae55 in ___nanosleep () from /usr/lib/libc.so.1
(gdb) bt
#0  0xfeeeae55 in ___nanosleep () from /usr/lib/libc.so.1
#1  0xfeedcae4 in sleep () from /usr/lib/libc.so.1
#2  0x080509ef in main () at a.c:17

如果嫌每次ps查看进程号比较麻烦，请尝试如下脚本

# 保存为xgdb.sh（添加可执行权限）
# 用法 xgdb.sh a 
prog_bin=$1
running_name=$(basename $prog_bin)
pid=$(/sbin/pidof $running_name)
gdb attach $pid

另一种是先启动gdb，然后用“attach”命令“附着”在进程上：

bash-3.2# gdb -q a
Reading symbols from /data/nan/a...done.
(gdb) attach 10210
Attaching to program `/data/nan/a', process 10210
[New process 10210]
Retry #1:
Retry #2:
Retry #3:
Retry #4:
Reading symbols from /usr/lib/libc.so.1...(no debugging symbols found)...done.
[Thread debugging using libthread_db enabled]
[New LWP    3        ]
[New LWP    2        ]
[New Thread 1 (LWP 1)]
[New Thread 2 (LWP 2)]
[New Thread 3 (LWP 3)]
Loaded symbols for /usr/lib/libc.so.1
Reading symbols from /lib/ld.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/ld.so.1
[Switching to Thread 1 (LWP 1)]
0xfeeeae55 in ___nanosleep () from /usr/lib/libc.so.1
(gdb) bt
#0  0xfeeeae55 in ___nanosleep () from /usr/lib/libc.so.1
#1  0xfeedcae4 in sleep () from /usr/lib/libc.so.1
#2  0x080509ef in main () at a.c:17

如果不想继续调试了，可以用“detach”命令“脱离”进程：

(gdb) detach
Detaching from program: /data/nan/a, process 10210
(gdb) bt
No stack.

详情参见gdb手册

贡献者

nanxiao