gdb多进程/多线程调试实战

gdb多进程调试

• set follow-fork-mode [parent|child] set detach-on-fork [on|off]

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

• 查询正在调试的进程：info inferiors
• 切换调试的进程： inferior +inferior number
• catch fork命令可以捕获进程的创建
• attach + pid ， 可以附到一个正在运行的进程上进行调试

gdb多线程调试

• show scheduler-locking //显示当前scheduler-locking
• set scheduler-locking [on/off/step] //设置scheduler-locking
  
  • on：只有当前调试线程运行，其他线程处于暂停状态。
  • off：当前调试线程外的其他线程一直在正常运行。
  • step：其他线程跟随当前调试线程运行，但具体怎么协同运行，测试中无法体现。
  • 注意：set scheduler-locking要处于线程运行环境下才能生效，也就是程序已经运行并且暂停在某个断点处，否则会出现“Target ‘exec’ cannot support this command.”这样的错误；而且经过测试，设置后的scheduler-locking值在整个进程内有效，不属于某个线程。

gdb多进程/多线程调试实战例子

b@b-VirtualBox:~/Documents/temp_test$ sudo gdb ./o_multi_thread_process [sudo] password for b: GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1Copyright (C) 2014 Free Software Foundation, Inc.License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>This is free software: you are free to change and redistribute it.There is NO WARRANTY, to the extent permitted by law.  Type "show copying"and "show warranty" for details.This GDB was configured as "x86_64-linux-gnu".Type "show configuration" for configuration details.For bug reporting instructions, please see:<http://www.gnu.org/software/gdb/bugs/>.Find the GDB manual and other documentation resources online at:<http://www.gnu.org/software/gdb/documentation/>.For help, type "help".Type "apropos word" to search for commands related to "word"...Reading symbols from ./o_multi_thread_process...done.(gdb) attach 3027Attaching to program: /home/b/Documents/temp_test/o_multi_thread_process, process 3027Reading symbols from /lib/x86_64-linux-gnu/libpthread.so.0...Reading symbols from /usr/lib/debug//lib/x86_64-linux-gnu/libpthread-2.19.so...done.done.[New LWP 3029][Thread debugging using libthread_db enabled]Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".Loaded symbols for /lib/x86_64-linux-gnu/libpthread.so.0Reading symbols from /lib/x86_64-linux-gnu/libc.so.6...Reading symbols from /usr/lib/debug//lib/x86_64-linux-gnu/libc-2.19.so...done.done.Loaded symbols for /lib/x86_64-linux-gnu/libc.so.6Reading symbols from /lib64/ld-linux-x86-64.so.2...Reading symbols from /usr/lib/debug//lib/x86_64-linux-gnu/ld-2.19.so...done.done.Loaded symbols for /lib64/ld-linux-x86-64.so.20x00007f5c9acb8dfd in nanosleep () at ../sysdeps/unix/syscall-template.S:8181  ../sysdeps/unix/syscall-template.S: No such file or directory.(gdb) set follow-fork-mode parent (gdb) set detach-on-fork off(gdb) catch forkCatchpoint 1 (fork)(gdb) rStarting program: /home/b/Documents/temp_test/o_multi_thread_process [Thread debugging using libthread_db enabled]Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".Catchpoint 1 (forked process 3002), 0x00007ffff78b7ee4 in __libc_fork ()    at ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c:130130 ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c: No such file or directory.(gdb) info inferiors   Num  Description       Executable        * 1    process 2998      /home/b/Documents/temp_test/o_multi_thread_process (gdb) b 14Breakpoint 2 at 0x7ffff78b7f5b: file ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c, line 14.(gdb) info breakpoints Num     Type           Disp Enb Address            What1       catchpoint     keep y                      fork, process 3002     catchpoint already hit 1 time2       breakpoint     keep y   0x00007ffff78b7f5b in __libc_fork                                                    at ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c:14(gdb) d 2(gdb) info breakpoints Num     Type           Disp Enb Address            What1       catchpoint     keep y                      fork, process 3002     catchpoint already hit 1 time(gdb) b multi_thread_process.cpp : 14Breakpoint 3 at 0x4007f4: file ./multi_thread_process.cpp, line 14.(gdb) cContinuing.[New process 3002][Thread debugging using libthread_db enabled]Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".Reading symbols from /usr/lib/debug/lib/x86_64-linux-gnu/libpthread-2.19.so...done.Reading symbols from /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.19.so...done.Reading symbols from /usr/lib/debug/lib/x86_64-linux-gnu/ld-2.19.so...done.Breakpoint 3, main (argc=1, argv=0x7fffffffe598) at ./multi_thread_process.cpp:1515    if(pid != 0)(gdb) info inferiors   Num  Description       Executable          2    process 3002      /home/b/Documents/temp_test/o_multi_thread_process * 1    process 2998      /home/b/Documents/temp_test/o_multi_thread_process (gdb) inferior 2[Switching to inferior 2 [process 3002] (/home/b/Documents/temp_test/o_multi_thread_process)][Switching to thread 2 (Thread 0x7ffff7fdf740 (LWP 3002))] 0  0x00007ffff78b7ee4 in __libc_fork () at ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c:130130 ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c: No such file or directory.(gdb) set scheduler-locking on(gdb) b multi_thread_process.cpp : 50Breakpoint 4 at 0x400916: multi_thread_process.cpp:50. (2 locations)(gdb) info threads   Id   Target Id         Frame * 2    Thread 0x7ffff7fdf740 (LWP 3002) "o_multi_thread_" 0x00007ffff78b7ee4 in __libc_fork ()    at ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c:130  1    Thread 0x7ffff7fdf740 (LWP 2998) "o_multi_thread_" main (argc=1, argv=0x7fffffffe598)    at ./multi_thread_process.cpp:15(gdb) cContinuing.Breakpoint 3, main (argc=1, argv=0x7fffffffe598) at ./multi_thread_process.cpp:1515    if(pid != 0)(gdb) info threads   Id   Target Id         Frame * 2    Thread 0x7ffff7fdf740 (LWP 3002) "o_multi_thread_" main (argc=1, argv=0x7fffffffe598)    at ./multi_thread_process.cpp:15  1    Thread 0x7ffff7fdf740 (LWP 2998) "o_multi_thread_" main (argc=1, argv=0x7fffffffe598)    at ./multi_thread_process.cpp:15(gdb) cContinuing.ProcessB: 3002 step1ProcessB: 3002 step2ProcessB: 3002 step3^CProgram received signal SIGINT, Interrupt.0x00007ffff78b7de0 in __nanosleep_nocancel () at ../sysdeps/unix/syscall-template.S:8181  ../sysdeps/unix/syscall-template.S: No such file or directory.(gdb) info threads   Id   Target Id         Frame * 2    Thread 0x7ffff7fdf740 (LWP 3002) "o_multi_thread_" 0x00007ffff78b7de0 in __nanosleep_nocancel ()    at ../sysdeps/unix/syscall-template.S:81  1    Thread 0x7ffff7fdf740 (LWP 2998) "o_multi_thread_" main (argc=1, argv=0x7fffffffe598)    at ./multi_thread_process.cpp:15(gdb) info inferiors   Num  Description       Executable        * 2    process 3002      /home/b/Documents/temp_test/o_multi_thread_process   1    process 2998      /home/b/Documents/temp_test/o_multi_thread_process (gdb) inferior 1[Switching to inferior 1 [process 2998] (/home/b/Documents/temp_test/o_multi_thread_process)][Switching to thread 1 (Thread 0x7ffff7fdf740 (LWP 2998))] 0  main (argc=1, argv=0x7fffffffe598) at ./multi_thread_process.cpp:1515    if(pid != 0)(gdb) list10    {11    int pid;12  13    pid = fork();14  15    if(pid != 0)16      processA();17    else18      processB();19  (gdb) rThe program being debugged has been started already.Start it from the beginning? (y or n) nProgram not restarted.(gdb) cContinuing.ProcessA: 2998 step1[New Thread 0x7ffff77f6700 (LWP 3017)]^CProgram received signal SIGINT, Interrupt.0x00007ffff78b7dfd in nanosleep () at ../sysdeps/unix/syscall-template.S:8181  ../sysdeps/unix/syscall-template.S: No such file or directory.(gdb) info threads   Id   Target Id         Frame   3    Thread 0x7ffff77f6700 (LWP 3017) "o_multi_thread_" clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:81  2    Thread 0x7ffff7fdf740 (LWP 3002) "o_multi_thread_" 0x00007ffff78b7de0 in __nanosleep_nocancel ()    at ../sysdeps/unix/syscall-template.S:81* 1    Thread 0x7ffff7fdf740 (LWP 2998) "o_multi_thread_" 0x00007ffff78b7dfd in nanosleep ()    at ../sysdeps/unix/syscall-template.S:81(gdb)