Dead-Pointer Defense Primitives: Methods available on every Godot::Object wrapper for defensive lifetime inspection.

Key Topics & Information

• object.alive? : Returns true if native C++ engine object is still valid
• object.destroyed? : Returns true if node was freed in GDScript or Godot
• object.check_alive! : Raises Godot::DisposedObjectError if freed

The Dead-Pointer Hazard: How standard bindings crash without stack traces and how Lapis defends against it.

If an entity (e.g. an enemy) is deleted in GDScript via queue_free(), standard C bindings retain a dangling raw pointer. Dereferencing this pointer triggers an immediate unrecoverable crash: ACCESS_VIOLATION (0xC0000005)

In Lapis, every virtual dispatch and reflection call invokes #check_alive!:

def check_alive! : Void
  return if @pointer.null?
  unless Bridge.is_instance_id_valid(@instance_id)
    @pointer = Pointer(Void).null
    raise Godot::DisposedObjectError.new("Cannot access disposed Godot object")
  end
end

Instead of crashing the game, you get a clean, catchable Crystal exception with full stack trace!

Defensive Coding Patterns: Checking #alive? when holding references to transient entities.

node Tower < Node2D do
  @target : Enemy? = nil

  def _physics_process(delta : Float64) : Void
    # Check alive before firing:
    if enemy = @target
      if enemy.alive?
        fire_at(enemy.global_position)
      else
        @target = nil # Clear stale reference
      end
    end
  end
end