gdb调试多进程和多线程命令（转）

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 != )
     processA();
   else
     processB();

   return ;
   }

 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 !=  )
     {
     printf("ProcessA: Can not create new thread.");
     }

   processAworker(NULL);
   sleep();
   }

 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:  step1
ProcessB:  step1
ProcessB:  step2
ProcessB:  step3
ProcessA:  thread  step2
ProcessA:  thread  step3
ProcessA:  thread  step2
ProcessA:  thread  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  (fork)
(gdb) r
[Thread debugging using libthread_db enabled]

Catchpoint  (forked process ), 0x00110424 in __kernel_vsyscall ()
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.47.el6.i686
(gdb) break test.c:
Breakpoint  at 0x8048546: file test.c, line .
(gdb) cont
[New process ]
[Thread debugging using libthread_db enabled]

Breakpoint , main (argc=, argv=0xbffff364) at test.c:
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.47.el6.i686
(gdb) info inferiors
  Num  Description       Executable
      process       /home/cnwuwil/labs/c-lab/test
*     process       /home/cnwuwil/labs/c-lab/test

2. 切换到子进程：

(gdb) inferior
[Switching to inferior  [process ] (/home/cnwuwil/labs/c-lab/test)]
[Switching to thread  (Thread 0xb7fe86c0 (LWP ))]
#  0x00110424 in ?? ()
(gdb) info inferiors
  Num  Description       Executable
*     process       /home/cnwuwil/labs/c-lab/test
      process       /home/cnwuwil/labs/c-lab/test
(gdb) inferior
[Switching to inferior  [process ] (/home/cnwuwil/labs/c-lab/test)]
[Switching to thread  (Thread 0xb7fe86c0 (LWP ))]
#  main (argc=, argv=0xbffff364) at test.c:
(gdb) info inferiors
  Num  Description       Executable
      process       /home/cnwuwil/labs/c-lab/test
*     process       /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:
Breakpoint  at 0x804867d: file test.c, line . ( locations)
(gdb) cont
ProcessA:  step1
[New Thread 0xb7fe7b70 (LWP )]
ProcessA:  thread  step2

Breakpoint , processAworker (arg=0x0) at test.c:
(gdb) info inferiors
  Num  Description       Executable
      process       /home/cnwuwil/labs/c-lab/test
*     process       /home/cnwuwil/labs/c-lab/test
(gdb) info threads
   Thread 0xb7fe7b70 (LWP )  0x00110424 in __kernel_vsyscall ()
   Thread 0xb7fe86c0 (LWP )  0x00110424 in ?? ()
*  Thread 0xb7fe86c0 (LWP )  processAworker (arg=0x0) at test.c:

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
[Switching to thread  (Thread 0xb7fe7b70 (LWP ))]#  0x00110424 in __kernel_vsyscall ()
(gdb) cont
ProcessA:  thread  step3
ProcessA:  thread  step2
[Switching to Thread 0xb7fe7b70 (LWP )]

Breakpoint , processAworker (arg=0x0) at test.c:
(gdb) info threads
*  Thread 0xb7fe7b70 (LWP )  processAworker (arg=0x0) at test.c:
   Thread 0xb7fe86c0 (LWP )  0x00110424 in ?? ()
   Thread 0xb7fe86c0 (LWP )  0x00110424 in __kernel_vsyscall ()
(gdb) thread 

转自：http://blog.csdn.net/pbymw8iwm/article/details/7876797