package ctypes-foreign

You can search for identifiers within the package.

in-package search v0.2.0

On This Page

Description
Readme
Dependencies (6)
Dev Dependencies (6)
Optional Dependencies
Used by (94)
Conflicts
Build status

Dynamic access to foreign C libraries using Ctypes

Install

dune-project

Dependency

github.com Readme Changelog Edit opam file Versions (6)

Authors

J

Jeremy Yallop

Maintainers

J

Jeremy Yallop <yallop@gmail.com>

Sources

0.24.0.tar.gz

sha256=249c5604c8554659761a7282db4ad200aa8c0fdc408cdb53102bd70feeb51955

md5=064316aaf508a9db203f114bb8401dee

Description

This installs the ctypes-foreign interface which uses libffi to provide dynamic access to foreign libraries.

Added to opam-repository: 13 Nov 2025

README

ctypes is a library for binding to C libraries using pure OCaml. The primary aim is to make writing C extensions as straightforward as possible.

The core of ctypes is a set of combinators for describing the structure of C types -- numeric types, arrays, pointers, structs, unions and functions. You can use these combinators to describe the types of the functions that you want to call, then bind directly to those functions -- all without writing or generating any C!

Usage

Suppose you want to bind to the following C functions:

   int sigemptyset(sigset_t *set);
   int sigfillset(sigset_t *set);
   int sigaddset(sigset_t *set, int signum);
   int sigdelset(sigset_t *set, int signum);
   int sigismember(const sigset_t *set, int signum);

Using ctypes you can describe the interfaces to these functions as follows:

   let sigemptyset = foreign "sigemptyset" (ptr sigset_t @-> returning int)
   let sigfillset = foreign "sigfillset" (ptr sigset_t @-> returning int)
   let sigaddset = foreign "sigaddset" (ptr sigset_t @-> int @-> returning int)
   let sigdelset = foreign "sigdelset" (ptr sigset_t @-> int @-> returning int)
   let sigismember = foreign "sigismember" (ptr sigset_t @-> int @-> returning int)

The names bound by this code have the types you might expect:

   val sigemptyset : sigset_t ptr -> int
   val sigfillset : sigset_t ptr -> int
   val sigaddset : sigset_t ptr -> int -> int
   val sigdelset : sigset_t ptr -> int -> int
   val sigismember : sigset_t ptr -> int -> int

That's all there is to it. Unlike the usual way of writing C extensions, there are no C "stub" functions to write, so there's much less opportunity for error.

The documentation and source distribution contain more complex examples, involving structs, unions, arrays, callback functions, and so on, and show how to create and use C values (like instances of sigset_t ptr) in OCaml.

Links

Building C libraries in OCaml with the dune ctypes stanza describes how to use ctypes with dune
Chapter 19: Foreign Function Interface of Real World OCaml describes ctypes
Modular Foreign Function Bindings introduces ctypes in the context of the Mirage library operating system
Tutorial
API documentation
Mailing list
Type-safe C bindings using ocaml-ctypes and stub generation introduces the Cstubs interface
Using Cstubs_structs shows how to use the Cstubs_structs module to reliably determine data layout
A modular foreign function interface is a research paper (extending an earlier paper) that presents the design of ctypes
FAQ

Dependencies (6)

conf-libffi >= "2.0.0"
conf-pkg-config
dune-configurator
ctypes = version
ocaml >= "4.07.0"
dune >= "3.9"

Dev Dependencies (6)

odoc with-doc
conf-fts with-test & os != "win32"
conf-ncurses with-test
ounit2 with-test
lwt with-test & >= "2.4.7"
integers with-test & >= "0.2.2"

Optional Dependencies

None

Used by (94)

Conflicts