Singapore's old spiky half moons

You only see these "spokes"(left) in old architecture in Singapore - spiky things in the shape of a half moon on upper floors or roofs of old buildings. I remember asking dad what they were when I was a kid. My dad said they were to prevent people from climbing into the house. I see these spiky structures in the old building at Balestier Road where I attend taichi classes. They are located at corners where one could climb over to next door, say from the lift landing to the next unit (if not for these structures). Some are even reinforced with barbed wires. So I guess my dad was right that they were some form of deterrents . 

So unless you are Spiderman, you won't be able to swing from one roof top to the next with these spiky "separators". Can some architect let me know the proper term of these structures, or their real functions (if I were wrong about them)?

Those half-moon spikes again. separating the units of terraced houses along Emerald Hill Road.