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gdb的细节是什么，它在调试代码时是否拥有一个线程？

我在主线程中设置了一个退出标志，并且在打印标志之前我已经加入了其他线程。当我在使用参数“-g”编译后使用 gdb 运行调试版本时，它看起来：

[Thread debugging using libthread_db enabled]
Input number of threads:5

Main thread id: 0xb7fda6c0, 
[New Thread 0xb7fd9b70 (LWP 9276)]
[New Thread 0xb75d8b70 (LWP 9277)]
[New Thread 0xb6bd7b70 (LWP 9278)]
[New Thread 0xb61d6b70 (LWP 9279)]
[New Thread 0xb57d5b70 (LWP 9280)]
I am thread 0xb6bd7b70, myorder 2, thread_exit.
I am thread 0xb61d6b70, myorder 3, thread_exit.
I am thread 0xb7fd9b70, myorder 0, thread_exit.
I am thread 0xb57d5b70, myorder 4, thread_exit.
I am thread 0xb75d8b70, myorder 1, thread_exit.
[Thread 0xb61d6b70 (LWP 9279) exited]
[Thread 0xb6bd7b70 (LWP 9278) exited]
[Thread 0xb75d8b70 (LWP 9277) exited]
[Thread 0xb7fd9b70 (LWP 9276) exited]
Main: completed join with thread 0xb7fd9b70 having a status of 0
Main: completed join with thread 0xb75d8b70 having a status of 1
Main: completed join with thread 0xb6bd7b70 having a status of 2
Main: completed join with thread 0xb61d6b70 having a status of 3
Main: completed join with thread 0xb57d5b70 having a status of 4
Main: lock will be destroy
Main: 9273, tlist will be free 
Main exit.
[Thread 0xb57d5b70 (LWP 9280) exited]

Program exited normally.
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.7.el6.i686 libgcc-4.4.4-13.el6.i686

GDB 提供有关线程“创建”和“退出”的信息。pthread_join()但是在主线程中调用并打印“Main exit”后总是有一个线程退出。为什么？是 gdb 使用的线程吗？

运行发布版，没什么特别的：

Input number of threads:5

Main thread id: 0xb77176c0, 
I am thread 0xb5913b70, myorder 3, thread_exit.
I am thread 0xb4f12b70, myorder 4, thread_exit.
I am thread 0xb6314b70, myorder 2, thread_exit.
I am thread 0xb6d15b70, myorder 1, thread_exit.
I am thread 0xb7716b70, myorder 0, thread_exit.
Main: completed join with thread 0xb7716b70 having a status of 0
Main: completed join with thread 0xb6d15b70 having a status of 1
Main: completed join with thread 0xb6314b70 having a status of 2
Main: completed join with thread 0xb5913b70 having a status of 3
Main: completed join with thread 0xb4f12b70 having a status of 4
Main: lock will be destroy
Main: tdata list will be free 
Main exit.
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1 回答 1

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gdb，调试代码时它是否拥有一个线程？

不。

在调用 pthread_join() 并在主线程中打印“主退出”后，总是有一个线程退出。为什么？

glibc 发送到 GDB 以告知它线程已退出的通知作为（几乎）线程执行的最后一件事发送。特别是，在退出线程通知主线程它已经退出之后（即在退出线程唤醒主线程之后）发送该通知。Main exit因此，在 GDB 注意到退出线程实际上已经退出之前，主线程被唤醒并打印也就不足为奇了。

我已经运行了很多次，每次“主退出”之后只有一个线程。

那证明不了。如果您运行程序 1,000,000 次，可能至少有一次运行 GDB 会注意到Main exit打印之前退出的线程。排序可能取决于您的系统有多少处理器，以及它们有多忙。这里真的没有什么（有趣的）可看的。

于 2012-07-13T18:45:13.337 回答