Module Stdlib.Obj

Operations on internal representations of values.

Not for the casual user.

type t
type raw_data = nativeint
val repr : 'a -> t
val obj : t -> 'a
val magic : 'a -> 'b
val is_block : t -> bool
val is_int : t -> bool
val tag : t -> int
val size : t -> int
val reachable_words : t -> int

Computes the total size (in words, including the headers) of all heap blocks accessible from the argument. Statically allocated blocks are excluded, unless the runtime system was configured with --disable-naked-pointers.

  • since 4.04
val field : t -> int -> t
val set_field : t -> int -> t -> unit

When using flambda:

set_field MUST NOT be called on immutable blocks. (Blocks allocated in C stubs, or with new_block below, are always considered mutable.)

The same goes for set_double_field and set_tag. However, for set_tag, in the case of immutable blocks where the middle-end optimizers never see code that discriminates on their tag (for example records), the operation should be safe. Such uses are nonetheless discouraged.

For experts only: set_field et al can be made safe by first wrapping the block in Sys.opaque_identity, so any information about its contents will not be propagated.

val set_tag : t -> int -> unit
  • deprecated Use with_tag instead.
val double_field : t -> int -> float
val set_double_field : t -> int -> float -> unit
val raw_field : t -> int -> raw_data
val set_raw_field : t -> int -> raw_data -> unit
val dup : t -> t
val truncate : t -> int -> unit
  • deprecated
val add_offset : t -> Int32.t -> t
val with_tag : int -> t -> t
val first_non_constant_constructor_tag : int
val last_non_constant_constructor_tag : int
val lazy_tag : int
val closure_tag : int
val object_tag : int
val infix_tag : int
val forward_tag : int
val no_scan_tag : int
val abstract_tag : int
val string_tag : int
val double_tag : int
val double_array_tag : int
val custom_tag : int
val final_tag : int
  • deprecated Replaced by custom_tag.
val int_tag : int
val out_of_heap_tag : int
val unaligned_tag : int
module Closure : sig ... end
module Extension_constructor : sig ... end
val extension_constructor : 'a -> extension_constructor
  • deprecated use Obj.Extension_constructor.of_val
val extension_name : extension_constructor -> string
  • deprecated use Obj.Extension_constructor.name
val extension_id : extension_constructor -> int
  • deprecated use Obj.Extension_constructor.id
module Ephemeron : sig ... end

Ephemeron with arbitrary arity and untyped