gdb调试多进程和多线程命令

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 <infer number>
   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

2. 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 <thread number>

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：

(gdb) inferior 2

[Switching to inferior 2 [process 3475] (/home/cnwuwil/labs/c-lab/test)]

[Switching to thread 2 (Thread 0xb7fe86c
4000
0 (LWP 3475))]

#0  0x00110424 in ?? ()

(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) inferior 1

[Switching to inferior 1 [process 3472] (/home/cnwuwil/labs/c-lab/test)]

[Switching to thread 1 (Thread 0xb7fe86c0 (LWP 3472))]

#0  main (argc=1, argv=0xbffff364) at test.c:14

(gdb) info inferiors

  Num  Description       Executable       

  2    process 3475      /home/cnwuwil/labs/c-lab/test

* 1    process 3472      /home/cnwuwil/labs/c-lab/test

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

原文地址：http://blog.csdn.net/pbymw8iwm/article/details/7876797