---
title: (foreign c) a portable foreign function interface for R7RS
version: 0.10.0
---

# (foreign c)

(foreign c) is a C foreign function interface (FFI) library for R7RS. It is
portable in the sense that it supports multiple implementations, as opposed to
being portable by conforming to some specification.

The new readme is a work in progress.

## Implementation support tables

### Primitives 1

|                  | c-size-of    | c-bytevector-u8-set! |c-bytevector-u8-ref | define-c-library    | c-bytevector? | define-c-procedure  |
|------------------|:------------:|:--------------------:|:------------------:|:-------------------:|:-------------:|:-------------------:|
| **Chibi**        | X            | X                    |X                   | X                   | X             | X                   |
| **Chicken**      | X            | X                    |X                   | X                   | X             | X                   |
| **Gauche**       | X            | X                    |X                   | X                   | X             | X                   |
| **Guile**        | X            | X                    |X                   | X                   | X             | X                   |
| **Kawa**         | X            | X                    |X                   | X                   | X             | X                   |
| **Mosh**         | X            | X                    |X                   | X                   | X             | X                   |
| **Racket**       | X            | X                    |X                   | X                   | X             | X                   |
| **Saggittarius** | X            | X                    |X                   | X                   | X             | X                   |
| **Stklos**       | X            | X                    |X                   | X                   | X             | X                   |
| **Ypsilon**      | X            | X                    |X                   | X                   | X             | X                   |

### Primitives 2

|                  | define-c-callback |
|------------------|:-----------------:|
| Chibi            |                   |
| **Chicken**      | X                 |
| Gauche           |                   |
| **Guile**        | X                 |
| Kawa             |                   |
| **Mosh**         | X                 |
| **Racket**       | X                 |
| **Saggittarius** | X                 |
| Stklos           |                   |
| **Ypsilon**      | X                 |

### Test files pass

|                  | primitives.scm | addressof.scm | callback.scm |
|------------------|:--------------:|:-------------:|-------------:|
| Chibi            | X              | X             |              |
| **Chicken**      | X              | X             | X            |
| Gauche           | X              | X             |              |
| **Guile**        | X              | X             | X            |
| Kawa             | X              | X             |              |
| Mosh             | X              | X             |              |
| Racket           | X              |               |              |
| **Saggittarius** | X              | X             | X            |
| Stklos           | X              | X             |              |
| Ypsilon          | X              | X             |              |

### Installation

Either download the latest release from
[releases page](https://git.sr.ht/~retropikzel/foreign-c/refs) or git clone
, preferably with a tag, and copy the "foreign" directory to your library
directory.

As an example assuming you have a project and your libraries live in directory
called snow in it:

    git clone https://git.sr.ht/~retropikzel/foreign-c --branch LATEST_VERSION
    mkdir -p snow
    cp -r foreign-c/foreign snow/
    make -C snow/foreign/c <SCHEME_IMPLEMENTATION_NAME>

With most implementations the make command does not compile anything. When that
is the case it will say "Nothing to build on SCHEME\_IMPLEMENTATION\_NAME."

## Documentation

### Types

Types are given as symbols, for example 'int8 or 'pointer.

- int8
- uint8
- int16
- uint16
- int32
- uint32
- int64
- uint64
- char
- unsigned-char
- short
- unsigned-short
- int
- unsigned-int
- long
- unsigned-long
- float
- double
- pointer
- callback
    - Callback function

### Primitives

(**c-type-size** _type_)

Returns the size of given C type.

(**define-c-library** _scheme-name_ _headers_ _object-name_ _options_)
define-c-procedure
define-c-callback
c-bytevector?
c-bytevector-u8-set!
c-bytevector-u8-ref
c-bytevector-pointer-set!
c-bytevector-pointer-ref


### c-bytevector
make-c-bytevector
make-c-null
c-null?
c-free
native-endianness
c-bytevector-s8-set!
c-bytevector-s8-ref
c-bytevector-s16-set!
c-bytevector-s16-ref
c-bytevector-s16-native-set!
c-bytevector-s16-native-ref
c-bytevector-u16-set!
c-bytevector-u16-ref
c-bytevector-u16-native-set!
c-bytevector-u16-native-ref
c-bytevector-s32-set!
c-bytevector-s32-ref
c-bytevector-s32-native-set!
c-bytevector-s32-native-ref
c-bytevector-u32-set!
c-bytevector-u32-ref
c-bytevector-u32-native-set!
c-bytevector-u32-native-ref
c-bytevector-s64-set!
c-bytevector-s64-ref
c-bytevector-s64-native-set!
c-bytevector-s64-native-ref
c-bytevector-u64-set!
c-bytevector-u64-ref
c-bytevector-u64-native-set!
c-bytevector-u64-native-ref
c-bytevector-sint-set!
c-bytevector-sint-ref
c-bytevector-uint-set!
c-bytevector-uint-ref
c-bytevector-ieee-single-set!
c-bytevector-ieee-single-native-set!
c-bytevector-ieee-single-ref
c-bytevector-ieee-single-native-ref
c-bytevector-ieee-double-set!
c-bytevector-ieee-double-native-set!
c-bytevector-ieee-double-ref
c-bytevector-ieee-double-native-ref
bytevector->c-bytevector
c-bytevector->bytevector
call-with-address-of

string->c-utf8
c-utf8->string