boost thread - use local variable as parameter - c++

Question

I'm writing a C++ class using boost threads. The purpose of the class is to start a new thread, generate in this thread every 2 seconds an object called LocationEstimatePF and call a callback function in another class, giving this LocationEstimatePF as parameter.
Something like this:
void Simulator::startSimulation() {
running_ = true;
sim_thread_ = new boost::thread(boost::bind(&Simulator::run, this));
}
void Simulator::run() {
for (;;) {
if(running_){
try {
//Generate estimate
LocationEstimatePF estimate(1,2,3,4,5);
engine_.updateLocationEstimate(estimate);
//Wait for 2 seconds for next estimate
boost::this_thread::sleep(boost::posix_time::milliseconds(2000));
} catch (boost::thread_interrupted&) {
return;
}
}
}
}
The engine and thread are defined as a member variable in the .h file as follows:
InMapsEngine& engine_;
boost::thread* sim_thread_;
And the callback method in the Engine class:
void updateLocationEstimate(const LocationEstimatePF& estimate) { Log::info("Test");};
Now when I run startSimulation() above, I get a segmentation fault. Now, I know that engine_ is correctly set, I can even call other methods without a problem. I believe the problem lies in the local variable, do you guys have any idea? The "Test" in the engine is never printed.
Here the stack trace:
I/DEBUG (11781): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 00000000
I/DEBUG (11781): r0 00000000 r1 66da3e68 r2 00000001 r3 00000000
I/DEBUG (11781): r4 001e8480 r5 00000000 r6 00000000 r7 40490000
I/DEBUG (11781): r8 62055ab0 r9 66da3e68 sl 3f800000 fp 40000000
I/DEBUG (11781): ip 00000001 sp 66da3e60 lr 61864604 pc 616b0a4e cpsr 60000030
I/DEBUG (11781): d0 4158b82020000000 d1 3f110612c247fff9
I/DEBUG (11781): d2 400b8ae93f57e022 d3 400b8ae943697f55
I/DEBUG (11781): d4 c2ef3a464385c588 d5 407eb7ac40c0a412
I/DEBUG (11781): d6 40dd1ce4bec8a7a3 d7 0062e080400b8ae9
I/DEBUG (11781): d8 3fd9b1b440400000 d9 0000000000000000
I/DEBUG (11781): d10 0000000000000000 d11 0000000000000000
I/DEBUG (11781): d12 0000000000000000 d13 0000000000000000
I/DEBUG (11781): d14 0000000000000000 d15 0000000000000000
I/DEBUG (11781): d16 3fe0000000000000 d17 4158b82000000000
I/DEBUG (11781): d18 3fd7e1cb1c913900 d19 3fc41a88bb99a35a
I/DEBUG (11781): d20 0000000000000000 d21 3fac47489540ee39
I/DEBUG (11781): d22 3f8293cfee13fd75 d23 3f96eb1df9afa780
I/DEBUG (11781): d24 3f5871d465fee876 d25 3f6e1beddd51e95d
I/DEBUG (11781): d26 3f30d636137869f2 d27 3f439d2605c8ef21
I/DEBUG (11781): d28 3fe66819a15509c2 d29 3f13d11c3e64b4a4
I/DEBUG (11781): d30 bef375cbdb605373 d31 3f8b5c41074afda1
I/DEBUG (11781): scr 80000093
I/DEBUG (11781):
I/DEBUG (11781): backtrace:
I/DEBUG (11781): #00 pc 00367a4e /data/app-lib/de.tum.ei.lmt.inmaps3d-1/libInMapsJNI.so (Simulator::run()+69)
I/DEBUG (11781): #01 pc 0051b600 /data/app-lib/de.tum.ei.lmt.inmaps3d-1/libInMapsJNI.so
I/DEBUG (11781):
I/DEBUG (11781): stack:
I/DEBUG (11781): 66da3e20 83a88000
I/DEBUG (11781): 66da3e24 02ed263d
I/DEBUG (11781): 66da3e28 83a88000
I/DEBUG (11781): 66da3e2c 02ed263d
I/DEBUG (11781): 66da3e30 61f05dd3
I/DEBUG (11781): 66da3e34 0004f4cf
I/DEBUG (11781): 66da3e38 532719d5 /dev/ashmem/dalvik-mark-stack (deleted)
I/DEBUG (11781): 66da3e3c 176a6e38
I/DEBUG (11781): 66da3e40 61c0ee99 /data/app-lib/de.tum.ei.lmt.inmaps3d-1/libInMapsJNI.so
I/DEBUG (11781): 66da3e44 001e8480
I/DEBUG (11781): 66da3e48 00000000
I/DEBUG (11781): 66da3e4c 00000000
I/DEBUG (11781): 66da3e50 40490000 /system/lib/libskia.so (GrGLCaps::initStencilFormats(GrGLContextInfo const&)+808)
I/DEBUG (11781): 66da3e54 62055ab0
I/DEBUG (11781): 66da3e58 df0027ad
I/DEBUG (11781): 66da3e5c 00000000
I/DEBUG (11781): #00 66da3e60 001e8480
I/DEBUG (11781): 66da3e64 00000000
I/DEBUG (11781): 66da3e68 00000000
I/DEBUG (11781): 66da3e6c 00000000
I/DEBUG (11781): 66da3e70 00000000
I/DEBUG (11781): 66da3e74 00000000
I/DEBUG (11781): 66da3e78 00000000
I/DEBUG (11781): 66da3e7c 00000000
I/DEBUG (11781): 66da3e80 3f800000
I/DEBUG (11781): 66da3e84 40000000
I/DEBUG (11781): 66da3e88 40400000 /system/lib/libskia.so
I/DEBUG (11781): 66da3e8c 00000000
I/DEBUG (11781): 66da3e90 00000000
I/DEBUG (11781): 66da3e94 40490000 /system/lib/libskia.so (GrGLCaps::initStencilFormats(GrGLContextInfo const&)+808)
I/DEBUG (11781): 66da3e98 00000000
I/DEBUG (11781): 66da3e9c 16c16c17

Answer 1

Your InMapsEngine reference is not initialized or do you set it up outside of the class constructor ?
InMapsEngine & engine_;
You could use member object instead
InMapsEngine engine_;
... or set your reference before the thread calls it.

Answer 2

It's hard to tell from your stacktrace exactly what is going wrong, but it could be that you have multiple threads trying to access your shared engine resource at the same time.
One way to do this would be to use a mutex and condition variable to signal to your threads when your engine resource is available to them.:
try{
boost::mutex::scoped_lock lock(engine_mutex);
m_condition.wait(lock);
engine_.updateLocationEstimate(estimate);
m_condition.notify_one();
}
catch (boost::thread_interrupted&) {
return;
}
boost::this_thread::sleep(boost::posix_time::milliseconds(2000));
Though you may want to use a regular lock instead if you want to include your sleep in the try block. Just remember to unlock.