`GC.malloc_uninitialized` (untested)

gc_malloc_uninitialized.cr

lib LibGC
  GC_DS_LENGTH = 0

  fun GC_new_free_list : Void**
  fun GC_new_kind(freelist : Void**, descr : GC_word, adjust : Int, clear : Int) : UInt
  fun GC_generic_malloc(SizeT, knd : UInt) : Void*
end

module GC
  UNINITIALIZED_OBJ_KIND = LibGC.GC_new_kind(LibGC.GC_new_free_list, descr: LibGC::GC_DS_LENGTH, adjust: 1, clear: 0)

  # Same as `.malloc` but doesn't zero the memory.
  def self.malloc_uninitialized(size : LibC::SizeT) : Void*
    LibGC.GC_malloc_generic(size, UNINITIALIZED_OBJ_KIND)
  end
end