Module Dynlink

module Dynlink: sig .. end
Dynamic loading of bytecode object files.


val init : unit -> unit
Initialize the Dynlink library. Must be called before any other function in this module.

Dynamic loading of compiled bytecode files

val loadfile : string -> unit
Load the given bytecode object file (.cmo file) or bytecode library file (.cma file), 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.

Access control

val allow_only : string list -> unit
allow_only units restricts the compilation units that dynamically-linked units can reference: it only allows references to the units named in list units. References to any other compilation unit will cause a Unavailable_unit error during loadfile or loadfile_private.

Initially (just after calling init), all compilation units composing the program currently running are available for reference from dynamically-linked units. allow_only can be used to grant access to some of them only, 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.

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.

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 Objective Caml standard library directory.
val clear_available_units : unit -> unit
Empty the list of compilation units accessible to dynamically-linked programs.

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
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.