Access Violation When JPH::PhysicsSystem Is Destroyed.

Access Violation when JPH::PhysicsSystem is Destroyed: A Deep Dive

Introduction

When working with complex physics systems, it's not uncommon to encounter issues that can be difficult to diagnose. One such issue is the access violation that occurs when the JPH::PhysicsSystem is destroyed. In this article, we'll delve into the root cause of this problem and explore possible solutions.

The Problem

The issue arises when the program is terminated with an access violation, as shown in the following code snippet:

int main()
{
    JPH::PhysicsSystem physics_system;

    return 0;
}

This simple program creates an instance of JPH::PhysicsSystem and then immediately terminates. However, the program throws an access violation, indicating that something is amiss.

The IslandBuilder.h File

The error is located in the IslandBuilder.h file, which contains the following code:

struct BodyLink
{
    JPH_OVERRIDE_NEW_DELETE

    atomic<uint32> mLinkedTo; ///< An index in mBodyLinks pointing to another body in this island with a lower index than this body
    uint32 mIslandIndex; ///< The island index of this body (filled in during Finalize)
};

The JPH_OVERRIDE_NEW_DELETE macro is used to override the default new and delete operators for the BodyLink struct. However, this macro may not be working as intended, leading to the access violation.

The Reproducible Example

To reproduce this issue, you can clone the following GitHub repository: https://github.com/Please-just-dont/JoltPhysicsDestructorError. This repository contains a minimal reproducible example that demonstrates the access violation.

The Root Cause

After analyzing the code, it appears that the issue is caused by the fact that the JPH::PhysicsSystem destructor is not properly implemented. Specifically, the destructor is not releasing the memory allocated by the BodyLink struct.

The Solution

To fix this issue, we need to ensure that the JPH::PhysicsSystem destructor is properly implemented. We can do this by adding a custom destructor to the JPH::PhysicsSystem class that releases the memory allocated by the BodyLink struct.

Here's an updated version of the JPH::PhysicsSystem class with a custom destructor:

class JPH::PhysicsSystem
{
public:
    // ...

    ~PhysicsSystem()
    {
        // Release the memory allocated by the BodyLink struct
        for (auto& bodyLink : mBodyLinks)
        {
            delete bodyLink;
        }
    }

    // ...
};

By adding this custom destructor, we ensure that the memory allocated by the BodyLink struct is properly released when the JPH::PhysicsSystem object is destroyed.

Conclusion

In this article, we've explored the access violation that occurs when the JPH::PhysicsSystem is destroyed. We've identified the root cause of the issue and provided a solution by adding a custom destructor to the JPH::PhysicsSystem class. By following these steps, you should be able to fix this issue and ensure that your program runs without access violations.

Additional Tips

• When working with complex physics systems, it's essential to ensure that the destructors are properly implemented to release any allocated memory.
• Use a debugger to identify the source of the access violation and diagnose the issue.
• Consider using a memory profiler to detect any memory leaks or issues.

References

• JPH::PhysicsSystem
• IslandBuilder.h
• GitHub Repository
  Access Violation when JPH::PhysicsSystem is Destroyed: A Q&A Article

Introduction

In our previous article, we explored the access violation that occurs when the JPH::PhysicsSystem is destroyed. We identified the root cause of the issue and provided a solution by adding a custom destructor to the JPH::PhysicsSystem class. In this article, we'll answer some frequently asked questions (FAQs) related to this issue.

Q: What is an access violation?

A: An access violation is a type of runtime error that occurs when a program attempts to access memory that it is not allowed to access. This can happen when a program tries to read or write to memory that has already been freed or is not valid.

Q: Why does the JPH::PhysicsSystem destructor need to be implemented?

A: The JPH::PhysicsSystem destructor needs to be implemented to release the memory allocated by the BodyLink struct. If the destructor is not implemented, the memory will not be released, and the program will throw an access violation when it tries to access the memory.

Q: How do I implement a custom destructor for the JPH::PhysicsSystem class?

A: To implement a custom destructor for the JPH::PhysicsSystem class, you need to add a destructor function to the class that releases the memory allocated by the BodyLink struct. Here's an example of how you can do this:

class JPH::PhysicsSystem
{
public:
    // ...

    ~PhysicsSystem()
    {
        // Release the memory allocated by the BodyLink struct
        for (auto& bodyLink : mBodyLinks)
        {
            delete bodyLink;
        }
    }

    // ...
};

Q: Why do I need to use a for loop to release the memory allocated by the BodyLink struct?

A: You need to use a for loop to release the memory allocated by the BodyLink struct because the BodyLink struct is a container of pointers to memory. If you don't use a for loop, you'll only release the memory allocated by the first BodyLink struct, and the remaining BodyLink structs will still point to invalid memory.

Q: Can I use a delete[] statement to release the memory allocated by the BodyLink struct?

A: No, you should not use a delete[] statement to release the memory allocated by the BodyLink struct. The delete[] statement is used to release arrays of memory, but the BodyLink struct is a container of pointers to memory, not an array of memory.

Q: How do I debug an access violation in my program?

A: To debug an access violation in your program, you can use a debugger to identify the source of the access violation. Here are some steps you can follow:

1. Run your program under a debugger.
2. When the access violation occurs, the debugger will stop execution and display an error message.
3. Use the debugger to examine the memory locations that are being accessed.
4. Use the debugger to identify the source of the access violation.

Q: Can I use a memory profiler to detect access violations in my program?

A: Yes, you can use a memory profiler to detect access violations in your program. A memory profiler is a tool that can help you identify memory leaks and access violations in your program. Here are some steps you can follow:

1. Install a memory profiler on your system.
2. Run your program under the memory profiler.
3. The memory profiler will detect any memory leaks or access violations in your program.
4. Use the memory profiler to identify the source of the access violation.

Conclusion

In this article, we've answered some frequently asked questions (FAQs) related to the access violation that occurs when the JPH::PhysicsSystem is destroyed. We've provided information on how to implement a custom destructor for the JPH::PhysicsSystem class, how to debug an access violation, and how to use a memory profiler to detect access violations in your program. By following these steps, you should be able to fix this issue and ensure that your program runs without access violations.

Additional Tips

• Always use a debugger to identify the source of an access violation.
• Use a memory profiler to detect memory leaks and access violations in your program.
• Implement a custom destructor for any class that allocates memory.
• Use a for loop to release the memory allocated by a container of pointers to memory.