thread terminate called without an active exception

Question

I've been doing threaded networking for a game, but the server dies randomly, while i've been testing the networking so that I have several clients connecting and sending bunch of packets and disconnecting then connecting back again.

I am using c++ with SFML/Network and SFML/System threads. I have thread which listens for connections in the server once connection is established it creates two new threads for sending and receiving packets. The event handler and the send/receive threads share data with two std::queues. I've been trying to debug the crash with gdb, but i'm not that experienced with this so i'm looking for help.

Here is gdb console input when the crash happens.

OUT: 10 1 HELLO
IN: 10 0 LOLOLOL
OUT: 10 1 HELLO
IN: 10 0 LOLOLOL
OUT: 10 1 HELLO
Out thread killed by in thread!
In thread died!
New client connected!
[Thread 0x34992b70 (LWP 16167) exited]
[New Thread 0x3118bb70 (LWP 16186)]
terminate called without an active exception

Program received signal SIGABRT, Aborted.
[Switching to Thread 0x35193b70 (LWP 16166)]
0x00110416 in __kernel_vsyscall ()

Here is the backtrace:

(gdb) backtrace
#0  0x00110416 in __kernel_vsyscall ()
#1  0x46a0967f in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#2  0x46a0afb5 in abort () at abort.c:92
#3  0x47b8af0d in __gnu_cxx::__verbose_terminate_handler () at ../../../../libstdc++-v3/libsupc++/vterminate.cc:95
#4  0x47b88c84 in __cxxabiv1::__terminate (handler=0x47b8adc0 <__gnu_cxx::__verbose_terminate_handler()>) at ../../../../libstdc++-v3/libsupc++/eh_terminate.cc:40
#5  0x47b88cc0 in std::terminate () at ../../../../libstdc++-v3/libsupc++/eh_terminate.cc:50
#6  0x47b8878f in __cxxabiv1::__gxx_personality_v0 (version=1, actions=10, exception_class=890844228, ue_header=0x35193dc0, context=0x35192ea0)
    at ../../../../libstdc++-v3/libsupc++/eh_personality.cc:669
#7  0x46bdbfbe in _Unwind_ForcedUnwind_Phase2 (exc=0x35193dc0, context=0x35192ea0) at ../../../gcc/unwind.inc:175
#8  0x46bdc3a9 in _Unwind_ForcedUnwind (exc=0x35193dc0, stop=0x46b76fc0 <unwind_stop>, stop_argument=0x35193444) at ../../../gcc/unwind.inc:207
#9  0x46b794e2 in _Unwind_ForcedUnwind (exc=0x35193dc0, stop=0x46b76fc0 <unwind_stop>, stop_argument=0x35193444) at ../nptl/sysdeps/pthread/unwind-forcedunwind.c:132
#10 0x46b77141 in __pthread_unwind (buf=<optimized out>) at unwind.c:130
#11 0x46b6f5bb in __do_cancel () at ../nptl/pthreadP.h:265
#12 sigcancel_handler (sig=<optimized out>, si=<optimized out>, ctx=<optimized out>) at nptl-init.c:202
#13 sigcancel_handler (sig=32, si=0x35192f7c, ctx=0x35192ffc) at nptl-init.c:155
#14 <signal handler called>
#15 0x08049930 in out (data=0xb761c798) at src/layer7.cpp:40
#16 0x0804b8d7 in sf::priv::ThreadFunctorWithArg<void (*)(networkdata*), networkdata*>::Run (this=0xb761c7c8) at /usr/local/include/SFML/System/Thread.inl:48
#17 0x00116442 in sf::Thread::Run() () from /home/toni/ProjectRepos/sfml/build/lib/libsfml-system.so.2
#18 0x001166df in sf::priv::ThreadImpl::EntryPoint(void*) () from /home/toni/ProjectRepos/sfml/build/lib/libsfml-system.so.2
#19 0x46b70c5e in start_thread (arg=0x35193b70) at pthread_create.c:305
#20 0x46ab4b4e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:133

Here is the thread code from src/layer7.cpp

void out(networkdata * data) {
    bool running = true;
    while(running) {
        if(data->pipe_out->pipe_empty() == false) {
            sf::Packet packet = data->pipe_out->pop_message();
            if(data->socket->Send(packet) == sf::Socket::Disconnected) {
                data->thread_in->Terminate();
                std::cout << "In thread killed by out thread!" << std::endl;
                running = false;
            }
        }
    }
    std::cout << "Out thread died!" << std::endl;
}

Line 40 is the first if keyword after the while(running).
The data->pipe_out->pipe_empty() is call to the queue->empty()
The data->pipe_out->pop_message() is call which pops the front from the queue.
Then it sends the packet and checks if the connection is not disconnected
if socket is disconnected it terminates the "in" thread and stops the own thread.

Switch threads in gdb to get a different backtrace, maybe. — Lightness Races in Orbit
Actually i realized just now before checking your comments that i should probably lock data. :P — TMKCodes
Yeah, stupid me. It seems the bug was there. Seems to be working now. 5 Minutes been running already and before it crashed under a minute. — TMKCodes
You are getting a signal (look at the line that says "signal handler called"). I'm not sure which one, I don't trust the "sig=32" bit. This usually terminates your thread. Perhaps you should try use your own signal handlers. — n. 1.8e9-where's-my-share m.

Lightness Races in Orbit Lightness Races in Orbit · Accepted Answer · 2011-06-06T20:31:39

You need locks around data to protect against concurrent access to the same data structure from multiple threads.

thread terminate called without an active exception

2 Answers