Dynlink(3)

NAME
Dynlink - Dynamic loading of object files.

Module
Module Dynlink

Documentation

Module Dynlink
 : sig end

Dynamic loading of object files.

val is_native : bool

true if the program is native, false if the program is bytecode.

=== Dynamic loading of compiled files ===

val loadfile : string -> unit

In bytecode: load the given bytecode object file ( .cmo file) or bytecode library file ( .cma file), and link it with the running program. In native code: load the given OCaml plugin file (usually .cmxs ), and link it with the running program. All toplevel expressions in the loaded compilation units are evaluated. No facilities are provided to access value names defined by the unit. Therefore, the unit must register itself its entry points with the main program, e.g. by modifying tables of functions.

val loadfile_private : string -> unit

Same as loadfile , except that the compilation units just loaded are hidden (cannot be referenced) from other modules dynamically loaded afterwards.

val adapt_filename : string -> string

In bytecode, the identity function. In native code, replace the last extension with .cmxs .

=== Access control ===

val allow_only : string list -> unit

allow_only units restricts the compilation units that dynamically-linked units can reference: it forbids all references to units other than those named in the list units . References to any other compilation unit will cause a Unavailable_unit error during loadfile or loadfile_private .

Initially (or after calling default_available_units ) all compilation units composing the program currently running are available for reference from dynamically-linked units. allow_only can be used to restrict access to a subset of these units, e.g. to the units that compose the API for dynamically-linked code, and prevent access to all other units, e.g. private, internal modules of the running program. If allow_only is called several times, access will be restricted to the intersection of the given lists (i.e. a call to allow_only can never increase the set of available units).

val prohibit : string list -> unit

prohibit units prohibits dynamically-linked units from referencing the units named in list units . This can be used to prevent access to selected units, e.g. private, internal modules of the running program.

val default_available_units : unit -> unit

Reset the set of units that can be referenced from dynamically-linked code to its default value, that is, all units composing the currently running program.

val allow_unsafe_modules : bool -> unit

Govern whether unsafe object files are allowed to be dynamically linked. A compilation unit is 'unsafe' if it contains declarations of external functions, which can break type safety. By default, dynamic linking of unsafe object files is not allowed. In native code, this function does nothing; object files with external functions are always allowed to be dynamically linked.

=== Deprecated, low-level API for access control ===

val add_interfaces : string list -> string list -> unit

add_interfaces units path grants dynamically-linked object files access to the compilation units named in list units . The interfaces ( .cmi files) for these units are searched in path (a list of directory names).

val add_available_units : (string * Digest.t) list -> unit

Same as Dynlink.add_interfaces , but instead of searching .cmi files to find the unit interfaces, uses the interface digests given for each unit. This way, the .cmi interface files need not be available at run-time. The digests can be extracted from .cmi files using the extract_crc program installed in the OCaml standard library directory.

val clear_available_units : unit -> unit

Empty the list of compilation units accessible to dynamically-linked programs.

=== Deprecated, initialization ===

val init : unit -> unit

Deprecated. Initialize the Dynlink library. This function is called automatically when needed.

=== Error reporting ===

type linking_error =
 | Undefined_global of string
 | Unavailable_primitive of string
 | Uninitialized_global of string

type error =
 | Not_a_bytecode_file of string
 | Inconsistent_import of string
 | Unavailable_unit of string
 | Unsafe_file
 | Linking_error of string * linking_error
 | Corrupted_interface of string
 | File_not_found of string
 | Cannot_open_dll of string
 | Inconsistent_implementation of string

exception Error of error

Errors in dynamic linking are reported by raising the Error exception with a description of the error.

val error_message : error -> string

Convert an error description to a printable message.