Game locks up due to pathfinding not cleaning up old paths.

[Skyaero42]

Prerequisites

• I have searched for similar issues and confirmed this is not a duplicate

Game Version

• Command & Conquer Generals
• Command & Conquer Generals: Zero Hour
• Other (please specify below)

Bug Description

Game completely locks up. This happened in a recent game of Legionaire

Reproduction Steps

See attached replay. Happens around 1h:33m

Legi Defcon 6 lockup.zip

Additional Context

Initial investigation by @Mauller and @Caball009 yielded this is an issue with pathfinding not cleaned up
where during sorting in putOnSortedOpenList the game never breaks out of the following for-loop.

		// insertion sort
		PathfindCell *c, *lastCell = NULL;
		for( c = list; c; c = c->getNextOpen() )
		{
			if (c->m_info->m_totalCost > m_info->m_totalCost)
				break;

			lastCell = c;
		}

[Caball009]

link to source location

[Mauller]

So the problem here is due to the poor cleanup of the open and closed lists within some codepaths.
We are essentially getting a pathfinding cell that still has a reference to another cell.
The situation has then created a closed loop within the linked list as the pathfind info happens to link back to a later cell.

When i added an extra check in the loop to not exceed 500 cells, it prevented the deadlock.

The problem with this code should not exist within the fully fixed pathfinding as we correctly cleanup the open and closed lists and free and cleanup all pathfind info resources.

I can look at sorting a fix for this in the week and i will check for other places where deadlocks could occur due to the possible creation of infinite loops within linked lists.

The more difficult part is sensibly signaling that a pathfinding forced cleanup needs to occur due to where this is happening in the code.