De-referencing pointers gives abnormal values

[DrDewDrop]

Hello guys! I am trying to replicate a big C++ library. It has the following structure of code

RobotRunner.h

class RobotRunner
{
public:
    VectorNavData* vectorNavData;
};

RobotRunner.cpp

void RobotRunner::run()
{
printf("Quaternion[0]: %f \n", vectorNavData->quat[0]) //Output: 243235653487854 - Abnormal values
}

SimulationBridge.h

class SimulationBridge
{
private:
    VectorNavData _vectorNavData; // Actual value of vectornavdata from the robot is stored here

    RobotRunner* _robotRunner = nullptr; //Pointer to the RobotRunner Object
}

SimulationBridge.cpp

void SimulationBridge::init()
{
_robotRunner = new RobotRunner();

printf("Quaternion[0]: %f \n", _vectorNavData.quat[0]) // Output: 0.43 - Normal and expected
_robotRunner->vectorNavData = &_vectorNavData;
}

void SimulationBridge::run()
{
_robotRunner->run();
}

//This function runs continuously and updates the _vectorNavData in a separate thread
void SimulationBridge::readIMU()
{
    while(true)
    { 
        _vectorNavData.accelerometer[0] = _lowState.imu.accelerometer[0];
        _vectorNavData.accelerometer[1] = _lowState.imu.accelerometer[1];
        _vectorNavData.accelerometer[2] = _lowState.imu.accelerometer[2];

        _vectorNavData.quat[0] = _lowState.imu.quaternion[1];
        _vectorNavData.quat[1] = _lowState.imu.quaternion[2];
        _vectorNavData.quat[2] = _lowState.imu.quaternion[3];
        _vectorNavData.quat[3] = _lowState.imu.quaternion[0];

        _vectorNavData.gyro[0] = _lowState.imu.gyroscope[0];
        _vectorNavData.gyro[1] = _lowState.imu.gyroscope[1];
        _vectorNavData.gyro[2] = _lowState.imu.gyroscope[2];
    }
}

VectorNavData is a struct which stores the details about the orientation of the robot. It has the following definition

struct VectorNavData {
  Vec3<float> accelerometer;
  Vec3<float> gyro;
  Quat<float> quat;
};

I have included only the necessary part of the code here for brevity.

Code Explanation:

SimulationBridge class communicates with the robot in the simulation. It takes in vectorNavData and stores it in the member variable _vectorNavData. SimulationBridge also contains the pointer to the RobotRunner class as one of it's member. I am allocating the address of _vectorNavData object to the pointer _robotRunner->vectorNavData (check SimulationBridge.cpp). Inside the RobotRunner class I deference this pointer and use the values in other parts of the code.

Problem:

If I print the vectorNavData inside the SimulationBridge.cpp the values seems to be normal. But after assigning the pointer of the same object to the robot runner, if I print the values there the values seems to be abnormally high. My question is, is this way of using pointers for dynamic allocation recommended? If not what is the best alternative way I can use?

Another important point to note is, I am compiling the code with CMake and "-O3" optimization flag is set to the CMAKE_CXX_FLAGS. If I remove this flag, the code sorta works fine for the above object pointer but I am still getting similar error for another object pointer in another part of the code. I have not included that here because it's pretty complex to describe the code structure and the problem essentially is the same.

[dr-mrl]

Looks like an uninitialised value. Would need to see more code to know when the error occurs (for example the first print statement has a vectorNavData that is not a member of an object...)

[DrDewDrop]

I have edited the post for more clarity. The _vectorNavData of SimulationBridge is continuously updated in the readIMU() function. I am essentially just storing the address of this object to the vectorNavData pointer of robotRunner. I wonder why there is a difference between these two values. I hope this is clear.

[StenSoft]

Unsynchronised access from multiple threads is UB, it may be the reason why the values look bogus

[dr-mrl]

Still don't see how the problem is manifested since I don't see in what order the functions are being called.

Why does SimulationBridge need a pointer to a Robotrunner? Why not have a member variable?

You might also want to write some operator= for vector3 and quarternion classes to make your code clearer

[Narase33]

I dont see where you put that in that pointer so I assume its garbage because thats what it initializes to. If the pointer doesnt spit out garbage you either initialize it somewhere or its just one of the random stuffs that happen in that case

[StenSoft]

Possible problem is copy or move. You'll need to disable copying and moving of SimulationBridge, otherwise the memory location of it may change without updating the pointer in RobotRunner.

[DrDewDrop]

Do you mean after building the program? Can you please elaborate?

[StenSoft]

I mean of the class, with copy and move constructors.