18. Bigloo -- Bigloo Libraries

18. Bigloo -- Bigloo Libraries

Browsing

Home: Bigloo
A ``practical Scheme compiler''
User manual for version 2.6b
December 2003

Previous chapter: The Java interface
Next chapter: Extending the Runtime System

Bigloo Libraries

18.1 Compiling and linking with a library
18.2 Library and SRFI
18.3 Library and inline functions
18.4 library and repl
18.5 Building a library
18.6 A complete library example
18.7 Library and modules

Chapters

  Acknowledgements
1. Table of contents
2. Overview of Bigloo
3. Modules
4. Core Language
5. Standard Library
6. Pattern Matching
7. Object System
8. Threads
9. Regular parsing
10. Lalr(1) parsing
11. Errors and Assertions
12. Eval and code interpretation
13. Macro expansion
14. Command Line Parsing
15. Explicit typing
16. The C interface
17. The Java interface
18. Bigloo Libraries
19. Extending the Runtime System
20. SRFIs
21. DSSSL support
22. Compiler description
23. User Extensions
24. Bigloo Development Environment
25. Global Index
26. Library Index
  Bibliography

Bigloo libraries are collections of global bindings (global variables and global functions). Bigloo libraries are build on the top of the host operating system (e.g. Unix) libraries. Because Bigloo uses modules, a library is not only a bundle of compiled codes and memory locations. A Bigloo library is splited into several files:

  • one heap that describes the locations of the library.
  • several host library files.
  • possibly, C header files.
  • possibly, a compiler initialization file.
Let's consider, for example, a library that implements the format Common Lisp facility. Let's suppose we name this library bformat. Using a Unix machine, the Bigloo library will consist of the following files:

  • bformat.heap: the heap file.
  • libbformat.a, libbformat.so, libbformat_u.a, libbformat_u.so: the Unix library files. The file names with a _u are libraries compiled in unsafe and optimized mode.
  • bformat.h: an include file.
18.1 Compiling and linking with a library

From the user stand point, using a library can be made two ways:

  • Using the Bigloo -library lib-name option where lib-name is the name of the Bigloo library (not the name of one of the Unix files implementing the library). The name of the library must be lower case. For instance:

    $ bigloo foo.scm -library bformat
  • Using the module clause library. This second solution prevent from using a special compilation option. For instance, this module will automatically compile and link with the bformat library:

    (module foo
       (library bformat))
    
    ...
    (format ...)
    
When a Bigloo library lib is used, Bigloo automatically searches if a file called lib.init exists. If such a file exits, it is loaded at compile-time. That file may specifies compilation flags.

When a Bigloo library lib is used, the Bigloo linker automatically searches for a library to be linked against the application. The name of the file containing the library depends on the operating system and the back-end used. For instance, under Unix, for a library called NAME, the Bigloo linker searches for a file called libNAME.a or libNAME.so in the compilation linker path when using the native back-end. It searches for a file NAME.zip when the JVM back-end is used.

18.2 Library and SRFI

Libraries are related to Scheme SRFIs. That is, when a library is used the SRFI implemented by the library is registered. Registered SRFIs may be tested by the cond-expand form (see SRFIs).

18.3 Library and inline functions

It is illegal for libraries to include inline functions that make use of new foreign types. By new foreign type, we mean foreign types that are defined inside the library. A library may contains inline functions but that inline functions must not even call function using foreign types in their prototypes. Including inline functions making use of foreign C type will make the compiler to fail when compiling user code. The compiler will fail prompting type errors. A library may contains non-inline functions that make use of new foreign types.

18.4 library and repl

It is possible to implement a "read-eval-print-loop" that is extended with the facilities implemented inside a library. Because of the Bigloo module initialization process a module that implements an extended "repl" must reference a least one of the binding of the library. For instance, here is a module that implements a "repl" with the format facility available:

(module format-repl
   (library format))

;; a dummy reference to a facility of the format library
(let ((dummy format))
   (repl)


18.5 Building a library

Bigloo libraries require several steps before being completed.

  • The first step is to build a library heap. This is achieved using a special compilation mode: -mkaddheap -mkaddlib -addheap. That is, for your library you have to create a heap associated source file that imports all the binding you want in your library. The heap source file must be excluded from the source files that will be used to build the host library.

    Suppose we have a unique source file for the bformat library. The module clause of this source file is:

    (module __format
       (export (format . args)
               format:version
               ...
       (eval   (export format)
               (export format:version)
               ...
    
    Prior to compiling the library, we have to create the heap associated file (let's name it make-lib.scm). This file could be:

    (module __make-lib
       (import (__format "format.scm")))
    
    Building it is simple:

    bigloo -unsafe -q -mkaddheap -mkaddlib \
         make-lib.scm -addheap format.heap
    The option -mkaddheap and -mkaddlib tell Bigloo that it is compiling an heap associated file. The option -addheap tells Bigloo the name of the heap file to be produced.

  • The second step is to compile all the library source file. These compilation must be done using the -mkaddlib compilation mode. For example:

    bigloo -O3 -unsafe -mkaddlib              \
       -cc gcc -fsharing -q -rm               \
       -unsafev bformat.scm -o bformat_u.o -c
    bigloo -O3 -mkaddlib -g -cg -cc gcc       \
       -fsharing -q -rm                       \
       -unsafev bformat.scm -o bformat.o -c
    The first compilation produces the unsafe version the second the produced the debugging version.

  • The third step is to build the host operating system libraries. There is no portable way to do this. This operation may looks like:

    ar qcv libformat.a format.o
    ranlib libformat.a
    ld -G -o libformat.so format.o -lm -lc
    ar qcv libformat_u.a format_u.o
    ranlib libformat_u.a
    ld -G -o libformat_u.so format_u.o -lm -lc
At this time, you are ready to use your library. The Bigloo distribution contains library exemplar. Considering these examples as a departure point for new libraries is probably a good idea.

18.6 A complete library example

For the means of an example let's suppose we want to design a Bigloo library for 2d points. That library is made of three implementation files: two C files, point.h and point.c and one Scheme file scm-point.scm. Here are defined the three files:

point.h:
struct point_2d {
   double x, y;
};
point.c:
#include <stdio.h>
#include "point.h"

int print_point_2d( struct point_2d *pt ) {
   printf( "<point-2d: %g, %g>", pt->x, pt->y );
}
scm-point.scm:
(module point
   (include "point.sch")
   (extern  (include "point.h"))
   (export  (make-point::s-point_2d* ::double ::double)
            (print-point             ::s-point_2d*)
            (point?                  ::obj))
   (eval    (export-all)))

(define (make-point::s-point_2d* x::double y::double)
   (s-point_2d* x y))

(define (print-point p::s-point_2d*)
   (print_point_2d p))

(define (point? obj::obj)
   (s-point_2d*? obj)
   obj)
We want our library to be composed of the whole exported Scheme functions. Thus the file to build the heap library could look like:

(module __make-point-lib
   (import (point "scm-point.scm")))
Let's suppose that the point library requires the libposix library. This means that any file linked with the point library needs to be also linked with the posix library. Furthermore, programs making use of the point library needs to include the point.sch file. That Scheme file needs in turn the C file point.h otherwise the produced C files won't compile. The need for the libposix library and for the point.h file may be specified inside the point.init file. For our current library, the point.init file could look like:

(set! *ld-options*
      (string-append "-L/usr/lib " *ld-options*))

(set! *bigloo-user-lib*
      (cons "-lposix" *bigloo-user-lib*))

(set! *additional-include-foreign*
      (cons "point.h" *additional-include-foreign*))
      
(define-macro (point x y)
   `(make-point ,x ,y))
This file updates some compilation variables (*ld-options*, *bigloo-user-lib*, *additional-include-foreign*) and defines a macro: point. Because the point.init file will be loaded each time a compilation require the point library is spawned, user code are allowed to use the point macro. Here is an example file making use of the point library:

(module example
   (include "point.sch"))

(let ((p (point 2.9 3.5)))
   (print "point?: " (point? p))
   (print "point?: " (point? 4))
   (print-point p)
   (print (eval `(point? ,p)))
   (eval `(print-point ,p))
   (print "done..."))
To conclude that example here is the Makefile used to compile the point library, heap file and one example.

# bigloo flags
BIGLOO          = bigloo
BHEAPFLAGS      = -unsafe -q -mkaddheap -mkaddlib -v2
BCOMMONFLAGGS   = -mkaddlib -fsharing -q $(VERBOSE)        \
                  -copt '$(CCOMMONFLAGS)' -cc $(CC)
BSAFEFLAGS      = $(BCOMMONFLAGGS) -cg -O3 -g -cg -unsafev \
                  -eval '(set! *indent* 4)' -rm
BUNSAFEFLAGS    = $(BCOMMONFLAGS) -O4 -unsafe

# cigloo flags
CIGLOO          = cigloo

# cflags
CC              = gcc
CCOMMONFLAGS    = -I.
CSAFEFLAGS      = $(CCOMMONFLAGS)
CUNSAFEFLAGS    = $(CCOMMONFLAGS) -O2

# library objects
SAFE_OBJECT     = olib/scm-point.o olib/point.o
UNSAFE_OBJECT   = olib_u/scm-point.o olib_u/point.o

all: heap lib example

heap: point.heap

point.heap: point.sch scm-point.scm
        $(BIGLOO) $(BHEAPFLAGS) make-lib.scm -addheap point.heap

lib: lib_u lib.a

lib.a: olib $(SAFE_OBJECT)
        ar qcv libpoint.a $(SAFE_OBJECT) 

lib_u: olib_u $(UNSAFE_OBJECT)
        ar qcv libpoint_u.a $(UNSAFE_OBJECT) 

olib:
        mkdir olib

olib_u:
        mkdir olib_u

olib_u/scm-point.o olib/scm-point.o: scm-point.scm
        $(BIGLOO) $(BSAFEFLAGS) $(<F) -o $*.o -c

olib_u/point.o olib/point.o: point.c
        $(CC) $(CSAFEFLAGS) $(<F) -o $*.o -c

point.sch: point.h point.c
        cigloo $^ > point.sch

example: heap lib
        $(BIGLOO) -v2 -L . -library point \
            -static-bigloo example.scm -o example

clean:
        -/bin/rm -f point.heap
        -/bin/rm -f point.sch scm-point.c
        -/bin/rm -fr olib olib_u
        -/bin/rm -f example example.c example.o
        -/bin/rm -f libpoint.a libpoint_u.a
18.7 Library and modules

A Bigloo library may be composed of several Bigloo modules (even if in our example only one module was used). The modules composing the library are free to import each other. Nevertheless, someone designing a Bigloo library should be aware that Bigloo importation creates dependences between modules. A module mod1 that imports a module mod2 depends on mod2 because mod1 requires mod2 to be initialized (i.e. mod1 calls to the initialization function of mod2). The result is that using import clauses inside modules composing a library may create a lot of dependencies between the object files that are used to build the associated Unix library. Dependencies should be avoided because they make the Unix linkers unable to produce small stand-alone programs. Instead of import clauses, use clauses should be preferred. Use clauses do not create dependencies because a module mod1 that uses a second module mod2 does not require mod2 to be initialized. Of course, it may happen situations where the initialization is mandatory and thus, the import must not be replaced with a use clause. The source code of the Bigloo library makes use of import and use clauses. The Bigloo standard library should be studied as an example.




This Scribe page has been generated by scribeinfo.
Last update Tue Dec 16 13:46:41 2003