It supports direct allocation via both the heap and the stack.

  type Vec = CStruct3[Double, Double, Double]

  val vec = stackalloc[Vec] // allocate c struct on stack
  !vec._1 = 10.0            // initialize fields
  !vec._2 = 20.0
  !vec._3 = 30.0
  length(vec)               // pass by reference

...and...

  @extern object stdlib {
    def malloc(size: CSize): Ptr[Byte] = extern
  }

  val ptr = stdlib.malloc(32)

http://www.scala-native.org/en/latest/

Otherwise it currently uses the Boehm GC.

One big area that needs more work:

  "Scala Native doesn’t yet provide libraries for parallel
   multi-threaded programming and assumes single-threaded    
   execution by default."