Lisp/C Integration in Eclipse

[This paper was presented at the 40th Anniversary of Lisp Conference, November 17, 1998, Berkeley, CA.]

The Eclipse Common Lisp system serves as a Lisp-to-C translator, an extendible Lisp library for C programmers, and a complete traditional top-level Lisp system implemented in portable C. Using Eclipse, hand-written or system-generated C calls to Lisp look like ordinary C function calls, and Lisp data can be manipulated as ordinary C data by programs. Conversely, C function calls look like ordinary function calls within Lisp programs. We describe how this is used, the technology that implements it, and list related work.

1: Introduction

2: Core Technologies

2.1: Identifiers

2.2: Representation

2.2.1: Objects

2.2.2: Functions

2.2.3: Multiple Values

2.2.4: Dynamic Environment

2.2.5: C Implementations

2.3: Memory Management

2.4: Function-Based Interface

2.4.1: CLOS-MOP

2.4.2: Initialization

3: Using Lisp from C

3.1: Direct Calls

3.2: Funcall

3.3: Example Of Generated Code

3.5: Other Lisp Utilities and Their Effect on Calling Lisp Functions

3.5.1: Eval

3.5.2: Load

3.5.3: Passing Lisp Data

4: Using C from Lisp

5: Past And Future

5.1: Related Work

5.2: Planned Work

Notes

References

Eclipse Common Lisp is a commercial implementation that makes the full ANSI language definition [Ansi] available to programmers in two ways: as a traditional top-level program featuring a read-eval-print loop, and as a C-callable library.[Stearns] The library uses normal C naming and function-calling conventions, is suitable for use directly by C programmers, and was used to implement the top-level program. In addition, the library and top-level contain a definition of COMPILE-FILE that generates human-readable, lintable C code that can be compiled and linked with the library. The generated code shares the same naming and calling conventions as the library, and, in fact, was used to generate the library C source code from Lisp source code.

This language implementation strategy provides the following benefits:

• Eclipse allows programmers to develop whole or partial applications in Lisp, and then translate the source to maintainable C code.

• Eclipse enables applications using system-supplied or user-written Lisp utilities to have the same delivery options with respect to executables, libraries, licensing, and so forth, as any other C program developed with the aid of a C-callable library.

• Eclipse integrates Lisp code with code developed in C or any C-compatible language. Eclipse enables Lisp code to easily call C and vice versa. C programs can hold, examine, pass and manipulate Eclipse created-Lisp data directly. An application's controlling main() program can be written in any language.

• Eclipse makes the capabilities of Lisp directly available to C programmers, who can treat both system-defined utilities and those produced by COMPILE-FILE as though they were part of any sophisticated C library.

• Eclipse can be easily ported to a wide variety of platforms, and runs on three Unix systems and 32-bit Windows (NT/95, and so forth), all from the same source code.

What follows is a description of how this is accomplished. Section 2 describes the core technologies Eclipse uses to integrate Lisp and C. Section 3 describes how Eclipse allows Lisp utilities to be used from C code, and gives an example of generated code. Section 4 describes how C utilities are used from Lisp code. Section 5 lists related work and suggests where this technology might be headed.