gdb调试多进程和多线程命令（转）

时间：2021-07-21 16:29:53

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

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