gdb调试多线程

#include <pthread.h> void* ThreadFun(void* arg) { int *value=static_cast<int*> (arg); std::cout<<"This is thread"<<*value<<std::endl; pthread_exit(0); } int main() { int ret=0; pthread_t thread_id1,thread_id2; int* v1=new int(1); int* v2=new int(2); ret = pthread_create(&thread_id1, NULL, ThreadFun, static_cast<void*>(v1)); //这里笔误,应为thread_id1 就是调试这里的错误 if (ret) { std::cout<<"Create pthread error!"<<std::endl; return 1; } ret = pthread_create(&thread_id2, NULL, ThreadFun, static_cast<void*>(v2)); if (ret) { std::cout<<"Create pthread error!"<<std::endl; return 1; } pthread_join(thread_id1, NULL); pthread_join(thread_id2, NULL); return 0; }

$ gdb gdbThreadTest//调试gdbThreadTest

加断点

(gdb) break 7
Breakpoint 1 at 0x400a19: file kangThread.cpp, line 7.
(gdb) break 35
Breakpoint 2 at 0x400b35: file kangThread.cpp, line 35.
(gdb) info break
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x0000000000400a19 in ThreadFun(void*) at kangThread.cpp:7
2       breakpoint     keep y   0x0000000000400b35 in main() at kangThread.cpp:35

开始运行

(gdb) r
Starting program: /home/kang/src/mulThread/kangThread 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Traceback (most recent call last):
  File "/usr/share/gdb/auto-load/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19-gdb.py", line 63, in <module>
    from libstdcxx.v6.printers import register_libstdcxx_printers
ImportError: No module named ‘libstdcxx‘
[New Thread 0x7ffff6fd5700 (LWP 2773)]
[Switching to Thread 0x7ffff6fd5700 (LWP 2773)]

Breakpoint 1, ThreadFun (arg=0x602010) at kangThread.cpp:7
warning: Source file is more recent than executable.
7       int *value=static_cast<int*> (arg);

查看线程信息

(gdb) info thread
[New Thread 0x7ffff67d4700 (LWP 2774)]
  Id   Target Id         Frame 
  3    Thread 0x7ffff67d4700 (LWP 2774) "kangThread" clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:81
* 2    Thread 0x7ffff6fd5700 (LWP 2773) "kangThread" ThreadFun (arg=0x602010) at kangThread.cpp:7
  1    Thread 0x7ffff7fda780 (LWP 2769) "kangThread" clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:81

可以看到ID为2的线程执行到了断点Breakpoint 1。可以看一下value的值

(gdb) n
8       std::cout<<"This is thread"<<*value<<std::endl;
(gdb) p *value
$2 = 1

切换到线程3,看一下线程3执行到了哪里

(gdb) c
Continuing.
1
[Switching to Thread 0x7ffff67d4700 (LWP 2774)]

Breakpoint 1, ThreadFun (arg=0x602030) at kangThread.cpp:7
7       int *value=static_cast<int*> (arg);
(gdb) info thread
  Id   Target Id         Frame 
* 3    Thread 0x7ffff67d4700 (LWP 2774) "kangThread" ThreadFun (arg=0x602030) at kangThread.cpp:7
  2    Thread 0x7ffff6fd5700 (LWP 2773) "kangThread" __GI__dl_debug_state () at dl-debug.c:74
  1    Thread 0x7ffff7fda780 (LWP 2769) "kangThread" 0x00007ffff7bc566b in pthread_join (threadid=140737337186048, 
    thread_return=0x0) at pthread_join.c:92
(gdb) thread 3
[Switching to thread 3 (Thread 0x7ffff67d4700 (LWP 2774))]
#0  ThreadFun (arg=0x602030) at kangThread.cpp:7
7       int *value=static_cast<int*> (arg);
(gdb) n
8       std::cout<<"This is thread"<<*value<<std::endl;
(gdb) p *value
$3 = 2

可以看出线程3的value为2。

还有其他许多命令和方法，要在实践中慢慢熟悉。

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gdb调试多线程

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