Random Chitchat 2012-2016

[Seadragon91]

I am not sure, but a int value shouldn't get increased by 2 threads without a lock. This happens on start of the server.
The line 98 in SpawnPrepare.cpp is: m_NumPrepared += 1.

Code:

==================
WARNING: ThreadSanitizer: data race (pid=20803)
  Write of size 4 at 0x7ffcb7d8d124 by main thread (mutexes: write M129381):
    #0 cSpawnPrepare::PreparedChunkCallback(int, int) /home/lukas/cpp/cuberite/src/SpawnPrepare.cpp:98 (Cuberite+0x00000069eeac)
    #1 cSpawnPrepareCallback::Call(int, int, bool) /home/lukas/cpp/cuberite/src/SpawnPrepare.cpp:25 (Cuberite+0x00000069f1cf)
    #2 cChunkMap::PrepareChunk(int, int, std::unique_ptr<cChunkCoordCallback, std::default_delete<cChunkCoordCallback> >) /home/lukas/cpp/cuberite/src/ChunkMap.cpp:2435 (Cuberite+0x00000060a96a)
    #3 cWorld::PrepareChunk(int, int, std::unique_ptr<cChunkCoordCallback, std::default_delete<cChunkCoordCallback> >) /home/lukas/cpp/cuberite/src/World.cpp:3140 (Cuberite+0x0000006d5861)
    #4 cSpawnPrepare::PrepareChunks(cWorld&, int, int, int) /home/lukas/cpp/cuberite/src/SpawnPrepare.cpp:63 (Cuberite+0x00000069eceb)
    #5 cWorld::InitializeSpawn() /home/lukas/cpp/cuberite/src/World.cpp:354 (Cuberite+0x0000006b9bea)
    #6 cRoot::StartWorlds() /home/lukas/cpp/cuberite/src/Root.cpp:418 (Cuberite+0x000000688e69)
    #7 UniversalMain(std::unique_ptr<cSettingsRepositoryInterface, std::default_delete<cSettingsRepositoryInterface> >) /home/lukas/cpp/cuberite/src/main.cpp:220 (Cuberite+0x0000006ddd9e)
    #8 main /home/lukas/cpp/cuberite/src/main.cpp:534 (Cuberite+0x0000006e2140)

  Previous write of size 4 at 0x7ffcb7d8d124 by thread T4:
    #0 cSpawnPrepare::PreparedChunkCallback(int, int) /home/lukas/cpp/cuberite/src/SpawnPrepare.cpp:98 (Cuberite+0x00000069eeac)
    #1 cSpawnPrepareCallback::Call(int, int, bool) /home/lukas/cpp/cuberite/src/SpawnPrepare.cpp:25 (Cuberite+0x00000069f1cf)
    #2 cLightingThread::LightChunk(cLightingThread::cLightingChunkStay&) /home/lukas/cpp/cuberite/src/LightingThread.cpp:327 (Cuberite+0x000000655ecc)
    #3 cLightingThread::Execute() /home/lukas/cpp/cuberite/src/LightingThread.cpp:228 (Cuberite+0x0000006558a1)
    #4 cIsThread::DoExecute() /home/lukas/cpp/cuberite/src/OSSupport/IsThread.cpp:74 (Cuberite+0x0000006f7d26)
    #5 void std::_Mem_fn<void (cIsThread::*)()>::operator()<, void>(cIsThread*) const /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/functional:569 (Cuberite+0x0000006f8505)
    #6 std::this_thread::__sleep_for(std::chrono::duration<long, std::ratio<1l, 1l> >, std::chrono::duration<long, std::ratio<1l, 1000000000l> >) <null> (libstdc++.so.6+0x00000008d38f)

  Location is stack of main thread.

  Mutex M129381 (0x7d3c0000d200) created at:
    #0 pthread_mutex_lock <null> (Cuberite+0x0000005900a0)
    #1 __gthread_mutex_lock(pthread_mutex_t*) /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../../include/x86_64-linux-gnu/c++/4.9/bits/gthr-default.h:748 (Cuberite+0x0000006f4f6d)
    #2 cChunkMap::Tick(std::chrono::duration<long, std::ratio<1l, 1000l> >) /home/lukas/cpp/cuberite/src/ChunkMap.cpp:2792 (Cuberite+0x00000060c05a)
    #3 cWorld::Tick(std::chrono::duration<long, std::ratio<1l, 1000l> >, std::chrono::duration<long, std::ratio<1l, 1000l> >) /home/lukas/cpp/cuberite/src/World.cpp:983 (Cuberite+0x0000006b5ad2)
    #4 cWorld::cTickThread::Execute() /home/lukas/cpp/cuberite/src/World.cpp:110 (Cuberite+0x0000006b5688)
    #5 cIsThread::DoExecute() /home/lukas/cpp/cuberite/src/OSSupport/IsThread.cpp:74 (Cuberite+0x0000006f7d26)
    #6 void std::_Mem_fn<void (cIsThread::*)()>::operator()<, void>(cIsThread*) const /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/functional:569 (Cuberite+0x0000006f8505)
    #7 std::this_thread::__sleep_for(std::chrono::duration<long, std::ratio<1l, 1l> >, std::chrono::duration<long, std::ratio<1l, 1000000000l> >) <null> (libstdc++.so.6+0x00000008d38f)

  Thread T4 (tid=20808, running) created by main thread at:
    #0 pthread_create <null> (Cuberite+0x000000571251)
    #1 std::thread::_M_start_thread(std::shared_ptr<std::thread::_Impl_base>, void (*)()) <null> (libstdc++.so.6+0x00000008d4d2)
    #2 cIsThread::Start() /home/lukas/cpp/cuberite/src/OSSupport/IsThread.cpp:86 (Cuberite+0x0000006f7d93)
    #3 cLightingThread::Start(cWorld*) /home/lukas/cpp/cuberite/src/LightingThread.cpp:118 (Cuberite+0x0000006553fe)
    #4 cWorld::Start() /home/lukas/cpp/cuberite/src/World.cpp:550 (Cuberite+0x0000006bda5d)
    #5 cRoot::StartWorlds() /home/lukas/cpp/cuberite/src/Root.cpp:417 (Cuberite+0x000000688e58)
    #6 UniversalMain(std::unique_ptr<cSettingsRepositoryInterface, std::default_delete<cSettingsRepositoryInterface> >) /home/lukas/cpp/cuberite/src/main.cpp:220 (Cuberite+0x0000006ddd9e)
    #7 main /home/lukas/cpp/cuberite/src/main.cpp:534 (Cuberite+0x0000006e2140)

SUMMARY: ThreadSanitizer: data race /home/lukas/cpp/cuberite/src/SpawnPrepare.cpp:98 cSpawnPrepare::PreparedChunkCallback(int, int)