removeBody leaves rigid-body constraints pointing at the deleted body

[peachtree0222]

Environment

• OS: Ubuntu 24.04.5 LTS, Linux 7.0.0-28-generic x86_64
• Compiler: GCC 11.5.0
• Python: 3.12.3
• Source: bulletphysics/bullet3 master at 63c4d67e337017f9d8b298c900e9aabdb69296e7
• PyBullet: built locally from that exact checkout

Description

Removing a maximal-coordinate rigid body does not remove btTypedConstraint objects or m_userConstraints entries that reference it. The multibody branch performs this cleanup, but the rigid-body branch deletes the body after a //todo: clear all other remaining data... comment.

Expected behavior: removeBody removes constraints whose endpoint is the removed body, just as the multibody path does.

Actual behavior: stepping immediately after removal exits with status 139. If a replacement rigid body is allocated first, the retained fixed constraint silently binds the replacement: a body created at x=5 moves to x=4.5 and its peer moves from x=1 to x=1.5. Removing the constraint before the body is a clean control and leaves both positions unchanged.

Source:

bullet3/examples/SharedMemory/PhysicsServerCommandProcessor.cpp

Lines 12739 to 12848 in 63c4d67

	bool PhysicsServerCommandProcessor::processRemoveBodyCommand(const struct SharedMemoryCommand& clientCmd, struct SharedMemoryStatus& serverStatusOut, char* bufferServerToClient, int bufferSizeInBytes)
	{
	bool hasStatus = true;
	SharedMemoryStatus& serverCmd = serverStatusOut;
	serverCmd.m_type = CMD_REMOVE_BODY_FAILED;
	serverCmd.m_removeObjectArgs.m_numBodies = 0;
	serverCmd.m_removeObjectArgs.m_numUserConstraints = 0;
	m_data->m_guiHelper->setVisualizerFlag(COV_ENABLE_SYNC_RENDERING_INTERNAL, 0);
	for (int i = 0; i < clientCmd.m_removeObjectArgs.m_numBodies; i++)
	{
	int bodyUniqueId = clientCmd.m_removeObjectArgs.m_bodyUniqueIds[i];
	InternalBodyHandle* bodyHandle = m_data->m_bodyHandles.getHandle(bodyUniqueId);
	if (bodyHandle)
	{
	#ifndef USE_DISCRETE_DYNAMICS_WORLD
	if (bodyHandle->m_multiBody)
	{
	serverCmd.m_removeObjectArgs.m_bodyUniqueIds[serverCmd.m_removeObjectArgs.m_numBodies++] = bodyUniqueId;
	if (m_data->m_pickingMultiBodyPoint2Point && m_data->m_pickingMultiBodyPoint2Point->getMultiBodyA() == bodyHandle->m_multiBody)
	{
	//memory will be deleted in the code that follows
	m_data->m_pickingMultiBodyPoint2Point = 0;
	}
	//also remove user constraints...
	for (int i = m_data->m_dynamicsWorld->getNumMultiBodyConstraints() - 1; i >= 0; i--)
	{
	btMultiBodyConstraint* mbc = m_data->m_dynamicsWorld->getMultiBodyConstraint(i);
	if ((mbc->getMultiBodyA() == bodyHandle->m_multiBody) || (mbc->getMultiBodyB() == bodyHandle->m_multiBody))
	{
	m_data->m_dynamicsWorld->removeMultiBodyConstraint(mbc);
	//also remove user constraint and submit it as removed
	for (int c = m_data->m_userConstraints.size() - 1; c >= 0; c--)
	{
	InteralUserConstraintData* userConstraintPtr = m_data->m_userConstraints.getAtIndex(c);
	int userConstraintKey = m_data->m_userConstraints.getKeyAtIndex(c).getUid1();
	if (userConstraintPtr->m_mbConstraint == mbc)
	{
	m_data->m_userConstraints.remove(userConstraintKey);
	serverCmd.m_removeObjectArgs.m_userConstraintUniqueIds[serverCmd.m_removeObjectArgs.m_numUserConstraints++] = userConstraintKey;
	}
	}
	delete mbc;
	}
	}
	if (bodyHandle->m_multiBody->getBaseCollider())
	{
	if (m_data->m_pluginManager.getRenderInterface())
	{
	m_data->m_pluginManager.getRenderInterface()->removeVisualShape(bodyHandle->m_multiBody->getBaseCollider()->getUserIndex3());
	}
	m_data->m_dynamicsWorld->removeCollisionObject(bodyHandle->m_multiBody->getBaseCollider());
	int graphicsIndex = bodyHandle->m_multiBody->getBaseCollider()->getUserIndex();
	m_data->m_guiHelper->removeGraphicsInstance(graphicsIndex);
	delete bodyHandle->m_multiBody->getBaseCollider();
	}
	for (int link = 0; link < bodyHandle->m_multiBody->getNumLinks(); link++)
	{
	btCollisionObject* colObj = bodyHandle->m_multiBody->getLink(link).m_collider;
	if (colObj)
	{
	if (m_data->m_pluginManager.getRenderInterface())
	{
	m_data->m_pluginManager.getRenderInterface()->removeVisualShape(bodyHandle->m_multiBody->getLink(link).m_collider->getUserIndex3());
	}
	m_data->m_dynamicsWorld->removeCollisionObject(bodyHandle->m_multiBody->getLink(link).m_collider);
	int graphicsIndex = bodyHandle->m_multiBody->getLink(link).m_collider->getUserIndex();
	m_data->m_guiHelper->removeGraphicsInstance(graphicsIndex);
	delete colObj;
	}
	}
	int numCollisionObjects = m_data->m_dynamicsWorld->getNumCollisionObjects();
	m_data->m_dynamicsWorld->removeMultiBody(bodyHandle->m_multiBody);
	numCollisionObjects = m_data->m_dynamicsWorld->getNumCollisionObjects();
	delete bodyHandle->m_multiBody;
	bodyHandle->m_multiBody = 0;
	serverCmd.m_type = CMD_REMOVE_BODY_COMPLETED;
	}
	#endif
	if (bodyHandle->m_rigidBody)
	{
	if (m_data->m_pluginManager.getRenderInterface())
	{
	m_data->m_pluginManager.getRenderInterface()->removeVisualShape(bodyHandle->m_rigidBody->getUserIndex3());
	}
	serverCmd.m_removeObjectArgs.m_bodyUniqueIds[serverCmd.m_removeObjectArgs.m_numBodies++] = bodyUniqueId;
	if (m_data->m_pickedConstraint && m_data->m_pickedBody == bodyHandle->m_rigidBody)
	{
	m_data->m_pickedConstraint = 0;
	m_data->m_pickedBody = 0;
	}
	//todo: clear all other remaining data...
	m_data->m_dynamicsWorld->removeRigidBody(bodyHandle->m_rigidBody);
	int graphicsInstance = bodyHandle->m_rigidBody->getUserIndex2();
	m_data->m_guiHelper->removeGraphicsInstance(graphicsInstance);
	delete bodyHandle->m_rigidBody;
	bodyHandle->m_rigidBody = 0;
	serverCmd.m_type = CMD_REMOVE_BODY_COMPLETED;
	}

Reproduction package:

rigid-body-removal-constraint-cleanup-poc.zip

Steps to reproduce

1. Build PyBullet from the commit above using poc/README.md.
2. Run the control, dangling, and reuse modes in separate processes.
3. Compare the exit statuses, constraint counts, and positions with poc/observed-output.txt.