gdb调试多进程和多线程命令

gdb调试多进程和多线程命令

原文地址：http://blog.youkuaiyun.com/pbymw8iwm/article/details/7876797

1. 默认设置下，在调试多进程程序时GDB只会调试主进程。但是GDB（>V7.0）支持多进程的

分别以及同时

调试，换句话说，GDB可以同时调试多个程序。只需要设置follow-fork-mode(默认值：parent)和detach-on-fork（默认值：on）即可。

follow-fork-mode	detach-on-fork	说明
parent	on	只调试主进程（GDB默认）
child	on	只调试子进程
parent	off	同时调试两个进程，gdb跟主进程，子进程block在fork位置
child	off	同时调试两个进程，gdb跟子进程，主进程block在fork位置

设置方法：set follow-fork-mode [parent|child] set detach-on-fork [on|off]

查询正在调试的进程：info inferiors

切换调试的进程： inferior

添加新的调试进程： add-inferior [-copies n] [-exec executable] ,可以用file executable来分配给inferior可执行文件。

其他：remove-inferiors infno， detach inferior

1. GDB默认支持调试多线程，跟主线程，子线程block在create thread。

   查询线程：info threads

   切换调试线程：thread

例程：

#include <stdio.h>

#include <pthread.h>

void processA();

void processB();

void * processAworker(void *arg);

int main(int argc, const char *argv[])

  {

  int pid;

  pid = fork();

  if(pid != 0)

    processA();

  else

    processB();

  return 0;

  }

void processA()

  {

  pid_t pid = getpid();

  char prefix[] = "ProcessA: ";

  char tprefix[] = "thread ";

  int tstatus;

  pthread_t pt;

  printf("%s%lu %s\n", prefix, pid, "step1");

  tstatus = pthread_create(&pt, NULL, processAworker, NULL);

  if( tstatus != 0 )

    {

    printf("ProcessA: Can not create new thread.");

    }

  processAworker(NULL);

  sleep(1);

  }

void * processAworker(void *arg)

  {

  pid_t pid = getpid();

  pthread_t tid = pthread_self();

  char prefix[] = "ProcessA: ";

  char tprefix[] = "thread ";

  printf("%s%lu %s%lu %s\n", prefix, pid, tprefix, tid, "step2");

  printf("%s%lu %s%lu %s\n", prefix, pid, tprefix, tid, "step3");

  return NULL;

  }

void processB()

  {

  pid_t pid = getpid();

  char prefix[] = "ProcessB: ";

  printf("%s%lu %s\n", prefix, pid, "step1");

  printf("%s%lu %s\n", prefix, pid, "step2");

  printf("%s%lu %s\n", prefix, pid, "step3");

  }

输出：

[cnwuwil@centos c-lab]$ ./test

​ ProcessA: 802 step1
​ ProcessB: 803 step1
​ ProcessB: 803 step2
​ ProcessB: 803 step3
​ ProcessA: 802 thread 3077555904 step2
​ ProcessA: 802 thread 3077555904 step3
​ ProcessA: 802 thread 3077553008 step2
​ ProcessA: 802 thread 3077553008 step3

调试：

1. 调试主进程，block子进程。

   (gdb) set detach-on-fork off
   (gdb) show detach-on-fork
   Whether gdb will detach the child of a fork is off.
   (gdb) catch fork
   Catchpoint 1 (fork)
   (gdb) r
   [Thread debugging using libthread_db enabled]
   Catchpoint 1 (forked process 3475), 0x00110424 in __kernel_vsyscall ()
   Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.47.el6.i686
   (gdb) break test.c:14
   Breakpoint 2 at 0x8048546: file test.c, line 14.
   (gdb) cont
   [New process 3475]
   [Thread debugging using libthread_db enabled]
   Breakpoint 2, main (argc=1, argv=0xbffff364) at test.c:14
   Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.47.el6.i686
   (gdb) info inferiors
   Num Description Executable
   2 process 3475 /home/cnwuwil/labs/c-lab/test
   * 1 process 3472 /home/cnwuwil/labs/c-lab/test

2. 切换到子进程：

3. 设断点继续调试主进程，主进程产生两个子线程：

   (gdb) break test.c:50
   Breakpoint 3 at 0x804867d: file test.c, line 50. (2 locations)
   (gdb) cont
   ProcessA: 3472 step1
   [New Thread 0xb7fe7b70 (LWP 3562)]
   ProcessA: 3472 thread 3086911168 step2
   Breakpoint 3, processAworker (arg=0x0) at test.c:50
   (gdb) info inferiors
   Num Description Executable
   2 process 3475 /home/cnwuwil/labs/c-lab/test
   * 1 process 3472 /home/cnwuwil/labs/c-lab/test
   (gdb) info threads
   3 Thread 0xb7fe7b70 (LWP 3562) 0x00110424 in __kernel_vsyscall ()
   2 Thread 0xb7fe86c0 (LWP 3475) 0x00110424 in ?? ()
   * 1 Thread 0xb7fe86c0 (LWP 3472) processAworker (arg=0x0) at test.c:50

4. 切换到主进程中的子线程，注意：线程2为前面产生的子进程

   (gdb) thread 3
   [Switching to thread 3 (Thread 0xb7fe7b70 (LWP 3562))]#0 0x00110424 in __kernel_vsyscall ()
   (gdb) cont
   ProcessA: 3472 thread 3086911168 step3
   ProcessA: 3472 thread 3086908272 step2
   [Switching to Thread 0xb7fe7b70 (LWP 3562)]
   Breakpoint 3, processAworker (arg=0x0) at test.c:50
   (gdb) info threads
   * 3 Thread 0xb7fe7b70 (LWP 3562) processAworker (arg=0x0) at test.c:50
   2 Thread 0xb7fe86c0 (LWP 3475) 0x00110424 in ?? ()
   1 Thread 0xb7fe86c0 (LWP 3472) 0x00110424 in __kernel_vsyscall ()
   (gdb) thread 1