Outdated CHICKEN release

This is a manual page for an old and unsupported version of CHICKEN. If you are still using it, please consider migrating to the latest version. You can find the manual for the latest release here.

manual

Extension libraries (eggs) are extensions to the core functionality provided by the basic CHICKEN system, to be built and installed separately. The mechanism for loading compiled extensions is based on dynamically loadable code and as such is only available on systems on which loading compiled code at runtime is supported. Currently these are most UNIX-compatible platforms that provide the libdl functionality like Linux, Solaris, BSD, Mac OS X and Windows using Cygwin.

Note: Extension may also be normal applications or shell scripts, but are usually libraries.

chicken-setup will download the source code for extension automatically from the canonical server at http://www.call-with-current-continuation.org/eggs if the requested egg does not exist in the current directory. Various command-line options exist for customizing the process and/or retrieving the egg from other locations or in other formats.

Installing extensions

To install an extension library, run the chicken-setup program with the extension name as argument. The extension archive is downloaded, its contents extracted and the contained setup script is executed. This setup script is a normal Scheme source file, which will be interpreted by chicken-setup. The complete language supported by csi is available, and the library units srfi-1 regex utils posix tcp are loaded. Additional libraries can be loaded at run-time.

The setup script should perform all necessary steps to build the new library (or application). After a successful build, the extension can be installed by invoking one of the procedures install-extension, install-program or install-script. These procedures will copy a number of given files into the extension repository or in the path where the CHICKEN executables are located (in the case of executable programs or scripts). Additionally the list of installed files, and user-defined metadata is stored in the repository.

If no extension name is given on the command-line, and if none of the options -list, -version, -repository (without argument), -program-path (without argument), -fetch, -fetch-tree or -docindex is given, then all .setup scripts in the current directory are processed.

Installing extensions that use libraries

Sometimes an extension requires a C library to compile. Compilation can fail when your system has this library in a nonstandard location. Luckily, normally Chicken searches in the default locations /usr and /usr/local, and in the prefix where Chicken itself was installed. Sometimes this is not enough, so you'll need to supply chicken-setup with some extra hints to the C compiler/linker. Here's an example:

 chicken-setup -c '-I/usr/pkg/include/mysql' -c '-L/usr/pkg/lib/mysql' -c '-L -R/usr/pkg/lib/mysql' mysql

This installs the mysql egg with the extra compiler options -I and -L to set the include path and the library search path. The second -L switch passes the -R option directly to the linker, which causes the library path to get hardcoded into the resulting extension file (for systems that do not use ld.so.conf).

Creating extensions

Extensions can be created by creating an (optionally gzipped) tar archive named EXTENSION.egg containing all needed files plus a .setup script in the root directory. After chicken-setup has extracted the files, the setup script will be invoked. There are no additional constraints on the structure of the archive, but the setup script has to be in the root path of the archive.

Procedures and macros available in setup scripts

install-extension

(install-extension ID FILELIST [INFOLIST])

Installs the extension library with the name ID. All files given in the list of strings FILELIST will be copied to the extension repository. It should be noted here that the extension id has to be identical to the name of the file implementing the extension. The extension may load or include other files, or may load other extensions at runtime specified by the require-at-runtime property.

FILELIST may be a filename, a list of filenames, or a list of pairs of the form (SOURCE DEST) (if you want to copy into a particular sub-directory - the destination directory will be created as needed). If DEST is a relative pathname, < it will be copied into the extension repository.

The optional argument INFOLIST should be an association list that maps symbols to values, this list will be stored as ID.setup-info at the same location as the extension code. Currently the following properties are used:

syntax

[extension property] (syntax)

Marks the extension as syntax-only. No code is compiled, the extension is intended as a file containing macros to be loaded at compile/macro-expansion time.

require-at-runtime

[extension property] (require-at-runtime ID ...)

Specifies extensions that should be loaded (via require) at runtime. This is mostly useful for syntax extensions that need additional support code at runtime.

version

[extension property] (version STRING)

Specifies version string.

documentation

[extension property] (documentation FILENAME)

The filename of a HTML document containing extension-specific documentation. This file should be given in the file-list passed to install-extension and a link to it will be automatically included in the index page (accessible via chicken-setup -docindex).

examples

[extension property] (examples FILENAME ...)

Copies the given files into the examples directory, which is usually $prefix/share/chicken/examples or (make-pathname (chicken-home) "examples")).

Note that the files listed in this property should not be listed in the normal list of files to install passed to install-extension. This is the only exception - other files that are installed in the repository must be given in the file list.

exports

[extension property] (exports EXPORT ...)

Add export-information to the generated extension-information. EXPORT may be a symbol naming an exported toplevel variable or a string designating a file with exported variables, as generated by the -emit-exports option or the emit-exports declaration specifier.

static

[extension property] (static STRING)

If the extension also provides a static library, then STRING should contain the name of that library. Used by csc when compiling with the -static-extensions option.

static-options

[extension property] (static-options STRING)

Additional options that should be passed to the linker when linking with the static version of an extension (see static above). Used by csc when compiling with the -static-extensions option.

All other properties are currently ignored. The FILELIST argument may also be a single string.

install-program

[procedure] (install-program ID FILELIST [INFOLIST])

Similar to install-extension, but installs an executable program in the executable path (usually /usr/local/bin).

install-script

[procedure] (install-script ID FILELIST [INFOLIST])

Similar to install-program, but additionally changes the file permissions of all files in FILELIST to executable (for installing shell-scripts).

run

[syntax] (run FORM ...)

Runs the shell command FORM, which is wrapped in an implicit quasiquote. (run (csc ...)) is treated specially and passes -v (if -verbose has been given to chicken-setup) and -feature compiling-extension options to the compiler.

compile

[syntax] (compile FORM ...)

Equivalent to (run (csc FORM ...)).

make

[syntax] (make ((TARGET (DEPENDENT ...) COMMAND ...) ...) ARGUMENTS)

A make macro that executes the expressions COMMAND ..., when any of the dependents DEPENDENT ... have changed, to build TARGET. This is the same as the make extension, which is available separately. For more information, see make.

patch

[procedure] (patch WHICH REGEX SUBST)

Replaces all occurrences of the regular expression REGEX with the string SUBST, in the file given in WHICH. If WHICH is a string, the file will be patched and overwritten. If WHICH is a list of the form OLD NEW, then a different file named NEW will be generated.

copy-file

[procedure] (copy-file FROM TO)

Copies the file or directory (recursively) given in the string FROM to the destination file or directory TO.

move-file

[procedure] (move-file FROM TO)

Moves the file or directory (recursively) given in the string FROM to the destination file or directory TO.

remove-file*

[procedure] (remove-file* PATH)

Removes the file or directory given in the string PATH.

find-library

[procedure] (find-library NAME PROC)

Returns #t if the library named libNAME.[a|so] (unix) or NAME.lib (windows) could be found by compiling and linking a test program. PROC should be the name of a C function that must be provided by the library. If no such library was found or the function could not be resolved, #f is returned.

find-header

[procedure] (find-header NAME)

Returns #t if a C include-file with the given name is available, or #f otherwise.

try-compile

[procedure] (try-compile CODE #!key cc cflags ldflags compile-only c++)

Returns #t if the C code in CODE compiles and links successfully, or #f otherwise. The keyword parameters cc (compiler name, defaults to the C compiler used to build this system), cflags and ldflags accept additional compilation and linking options. If compile-only is true, then no linking step takes place. If the keyword argument c++ is given and true, then the code will be compiled in C++ mode.

create-directory

[procedure] (create-directory PATH)

Creates the directory given in the string PATH, with all parent directories as needed.

chicken-prefix

[parameter] chicken-prefix

The installation prefix specified when CHICKEN was built.

installation-prefix

[parameter] installation-prefix

An alternative installation prefix that will be prepended to extension installation paths if specified. It is set by the -install-prefix option or environment variable CHICKEN_INSTALL_PREFIX.

program-path

[parameter] (program-path [PATH])

Holds the path where executables are installed and defaults to either $CHICKEN_PREFIX/bin, if the environment variable CHICKEN_PREFIX is set or the path where the CHICKEN binaries (chicken, csi, etc.) are installed.

setup-root-directory

[parameter] (setup-root-directory [PATH])

Contains the path of the directory where chicken-setup was invoked.

setup-build-directory

[parameter] (setup-build-directory [PATH])

Contains the path of the directory where the extension is built. This is not necessarily identical to setup-root-directory.

setup-verbose-flag

[parameter] (setup-verbose-flag [BOOL])

Reflects the setting of the -verbose option, i.e. is #t, if -verbose was given.

setup-install-flag

[parameter] (setup-install-flag [BOOL])

Reflects the setting of the --no-install option, i.e. is #f, if -no-install was given.

required-chicken-version

[procedure] (required-chicken-version VERSION)

Signals an error if the version of CHICKEN that this script runs under is lexicographically less than VERSION (the argument will be converted to a string, first).

required-extension-version

[procedure] (required-extension-version EXTENSION1 VERSION1 ...)

Checks whether the extensions EXTENSION1 ... are installed and at least of version VERSION1 .... The test is made by lexicographically comparing the string-representations of the given version with the version of the installed extension. If one of the listed extensions is not installed, has no associated version information or is of a version older than the one specified.

cross-chicken

[procedure] (cross-chicken)

Returns #t if this system is configured for cross-compilation or #f otherwise.

host-extension

[parameter] host-extension

For a cross-compiling CHICKEN, when compiling an extension, then it should be built for the host environment (as opposed to the target environment). This parameter is controlled by the -host-extension command-line option. A setup script should perform the proper steps of compiling any code by passing -host when invoking csc or using the compile macro.

Examples for extensions

The simplest case is a single file that does not export any syntax. For example

;;;; hello.scm

(define (hello name)
  (print "Hello, " name " !") )

We need a .setup script to build and install our nifty extension:

;;;; hello.setup

;; compile the code into a dynamically loadable shared object
;; (will generate hello.so)
(compile -s hello.scm)

;; Install as extension library
(install-extension 'hello "hello.so")

After entering

$ chicken-setup hello

at the shell prompt (and in the same directory where the two files exist), the file hello.scm will be compiled into a dynamically loadable library. If the compilation succeeds, hello.so will be stored in the repository, together with a file named hello.setup-info containing an a-list with metadata. If no extension name is given to chicken-setup, it will simply execute the first file with the .setup extension it can find.

Use it like any other CHICKEN extension:

$ csi -q
#;1> (require-extension hello)
; loading /usr/local/lib/chicken/1/hello.so ...
#;2> (hello "me")
Hello, me!
#;3>

Here we create a simple application:

;;;; hello2.scm

(print "Hello, ")
(for-each (lambda (x) (printf "~A " x)) (command-line-arguments))
(print "!")

We also need a setup script:

;;;; hello2.setup

(compile hello2.scm)  ; compile `hello2'
(install-program 'hello2 "hello2") ; name of the extension and files to be installed

To use it, just run chicken-setup in the same directory:

$ chicken-setup

(Here we omit the extension name)

Now the program hello2 will be installed in the same location as the other CHICKEN tools (like chicken, csi, etc.), which will normally be /usr/local/bin. Note that you need write-permissions for those locations and may have to run chicken-setup with administrative rights.

Uninstallation is just as easy:

$ chicken-setup -uninstall hello2

chicken-setup provides a make macro, so build operations can be of arbitrary complexity. When running chicken-setup with an argument NAME, for which no associated file NAME.setup, NAME.egg or NAME.scm exists will ask you to download the extension via HTTP from the default URL http://www.call-with-current-continuation.org/eggs. You can use the -host option to specify an alternative source location. Extensions that are required to compile and/or use the requested extension are downloaded and installed automatically.

If the given extension name contains a path prefix and the -host option is given, then chicken-setup can also download and install eggs from an arbitrary HTTP server. Alternatively you can pass a full URL (including the http:// prefix. Note that no dependency checks are done when downloading eggs directly with the URL syntax.

Finally a somewhat more complex example: We want to package a syntax extension with additional support code that is to be loaded at run-time of any Scheme code that uses that extension. We create a glass lambda, a procedure with free variables that can be manipulated from outside:

;;;; glass.scm

(define-macro (glass-lambda llist vars . body)
  ;; Low-level macros are fun!
  (let ([lvar (gensym)]
	[svar (gensym)] 
	[x (gensym)]
	[y (gensym)] 
	[yn (gensym)] )
    `(let ,(map (lambda (v) (list v #f)) vars)
       (define (,svar ,x . ,y)
	 (let* ([,yn (pair? ,y)]
		[,y (and ,yn (car ,y))] )
	   (case ,x
	     ,@(map (lambda (v)
		      `([,v] (if ,yn 
				 (set! ,v ,y)
				 ,v) ) )
		    vars)
	     (else (error "variable not found" ,x)) ) ) )
       (define ,lvar (lambda ,llist ,@body))
       (extend-procedure ,lvar ,svar) ) ) )

Here some support code that needs to be loaded at runtime:

;;;; glass-support.scm

(require-extension lolevel)

(define glass-lambda-accessor procedure-data)
(define (glass-lambda-ref gl v) ((procedure-data gl) v))
(define (glass-lambda-set! gl v x) ((procedure-data gl) v x))

The setup script looks like this:

(compile -s glass-support.scm)

(install-extension
  'glass
  '("glass.scm" "glass-support.so")
  '((syntax) (require-at-runtime glass-support)) )

The invocation of install-extension provides the files that are to be copied into the extension repository, and a metadata list that specifies that the extension glass is a syntax extension and that, if it is declared to be used by other code (either with the require-extension or require-for-syntax form), then client code should perform an implicit (require 'glass-support) at startup.

This can be conveniently packaged as an egg:

$ tar cfz glass.egg glass.setup glass.scm glass-support.scm

And now we use it:

$ chicken-setup glass
$ csi -quiet
#;1> (require-extension glass)
; loading /usr/local/lib/chicken/1/glass.scm ...
; loading /usr/local/lib/chicken/1/glass-support.so ...
#;2> (define foo (glass-lambda (x) (y) (+ x y)))
#;3> (glass-lambda-set! foo 'y 99)
#;4> (foo 33)
132

chicken-setup reference

Available options:

-h -help: Show usage information and exit.
-V -version: Display version and exit.
-R -repository [PATHNAME]: When used without an argument, the path of the extension repository is displayed on standard output. When given an argument, the repository pathname (and the repository-path parameter) will be set to PATHNAME for all subsequent operations. The default repository path is the installation library directory (usually /usr/local/lib/chicken), or (if set) the directory given in the environment variable CHICKEN_REPOSITORY. PATHNAME should be an absolute pathname.
-P -program-path [PATHNAME]: When used without an argument, the path for executables is displayed on standard output. When given an argument, the program path for installing executables and scripts will be set to PATHNAME for all subsequent operations. PATHNAME should be an absolute pathname.
-h -host HOSTNAME[:PORT]: Specifies alternative host for downloading extensions, optionally with a TCP port number (which defaults to 80).
-u -uninstall EXTENSION: Removes all files that were installed for EXTENSION from the file-system, together with any metadata that has been stored.
-l -list [NAME ...]: List all installed extensions or show extension information.
-r -run FILENAME: Load and execute given file.
-s -script FILENAME: Executes the given Scheme source file with all remaining arguments and exit. The she-bang shell script header is recognized, so you can write Scheme scripts that use chicken-setup just as with csi.
-e -eval EXPRESSION: Evaluates the given expression(s)
-v -verbose: Display additional debug information
-k -keep: Keep temporary files and directories
-c -csc-option OPTION: Passes OPTION as an extra argument to invocations of the compiler-driver (csc); this works only if csc is invoked as (run (csc ...))
-d -dont-ask: Do not ask the user before trying to download required extensions
-n -no-install: Do not install generated binaries and/or support files; any invocations of install-program, install-extension or install-script will be be no-ops
-i -docindex: Displays the path to the index-page of any installed extension-documentation; if the index page does not exist, it is created
-t -test EXTENSION ...: return success if all given extensions are installed
-ls EXTENSION: List installed files for extension
-fetch-tree: Download and print the repository catalog
-create-tree DIRECTORY: Create a fresh, minimal repository catalog and writes it to stdout
-t -test: If the extension sources contain a directory named tests and this directory includes a file named run.scm then this file is executed (with tests being the current working directory)
-tree FILENAME: Download and show the repository catalog
-svn URL: Fetch extension from Subversion repository
-svn-trunk URL: Fetch extension from trunk in Subversion repository
-revision REV: Specifies SVN revision to check out
-local PATHNAME: Fetch extension from local file
-install-prefix PATHNAME: Specify alternative installation prefix (for packaging)
-host-extension: Compile extension in "host" mode (sets the parameter host-extension to #f)
-build-prefix PATHNAME: Location where chicken-setup will create egg build directories (default: the value of environment variable CHICKEN_TMPDIR, or /tmp/chicken-{MAJOR-VERSION-build-{USER}})
-download-path PATHNAME: Location where chicken-setup will save downloaded files (default: build-prefix/downloads)
--: Ignore all following arguments

Note that the options are processed exactly in the order in which they appear in the command-line.

Windows notes

chicken-setup works on Windows, when compiled with Visual C++, but depends on the tar and gunzip tools to extract the contents of an egg. The best way is to download an egg either manually (or with chicken-setup -fetch) and extract its contents with a separate program (like winzip). The CHICKEN_REPOSITORY environment variable has to be set to a directory where your compiled extensions should be located.

The .setup scripts will not always work under Windows, and the extensions may require libraries that are not provided for Windows or work differently. Under these circumstances it is recommended to perform the required steps to build an extension manually.

The required UNIX tools are also available as Windows binaries. Google or ask on the CHICKEN mailing list if you need help locating them.

Security

When extensions are downloaded and installed one is executing code from potentially compromised systems. This applies also when chicken-setup executes system tests for required extensions. As the code has been retrieved over the network effectively untrusted code is going to be evaluated. When chicken-setup is run as root the whole system is at the mercy of the build instructions (note that this is also the case every time you install software via sudo make install, so this is not specific to the CHICKEN extension mechanism).

Security-conscious users should never run chicken-setup as root. A simple remedy is to set the environment variable CHICKEN_REPOSITORY, which will transparently place the repository at an arbitrary user-selected location. Alternatively obtain write/execute access to the default location of the repository (usually /usr/local/lib/chicken) to avoid running as root.

Other modes of installation

It is possible to install extensions directly from a Subversion repository or from a local checkout by using the -svn or -local options. By using either the svn client program (which must be installed) or file-system operations, all necessary files will be copied into the current directory (creating a subdirectory named EXTENSIONNAME.egg-dir), built and subsequently installed.

Dependency information, which is necessary to ensure required extensions are also installed, is downloaded automatically. If you have no internet connection or don't want to connect, you can also use a local file containing the necessary dependency information. The -fetch-tree option retrieves the canonical repository file at http://www.call-with-current-continuation.org/eggs/repository, writing it to stdout. Redirecting this output into a file and passing the file via the -tree option to chicken-setup allows you now to use the local repository file:

Retrieve complete extension repository (big):

% cd /opt
% svn co http://anonymous@//code.call-cc.org/svn/chicken-eggs/release/3 eggs

Get your own copy of the repository file:

% chicken-setup -fetch-tree >~/my-repository-file

Now you can install eggs from your local checkout, with full dependency tracking and without being connected to the internet:

% cd ~/tmp
% chicken-setup -local /opt/eggs -tree ~/my-repository-file opengl

Linking extensions statically

The compiler and chicken-setup support statically linked eggs. The general approach is to generate an object file or static library (in addition to the usual shared library) in your .setup script and install it along with the dynamically loadable extension. The setup properties static should contain the name of the object file (or static library) to be linked, when csc gets passed the -static-extensions option:

(compile -s -O2 -d1 my-ext.scm)   ; dynamically loadable "normal" version
(compile -c -O2 -d1 my-ext -unit my-ext)  ; statically linkable version
(install-extension
  'my-ext
  '("my-ext.so" "my-ext.o")
  '((static "my-ext.o")) )

Note the use of the -unit option in the second compilation step: static linking must use static library units. chicken-setup will perform platform-dependent file-extension translation for the file list, but does currently not do that for the static extension property.

To actually link with the static version of my-ext, do:

% csc -static-extensions my-program.scm -uses my-ext

The compiler will try to do the right thing, but can not handle all extensions, since the ability to statically link eggs is relatively new. Eggs that support static linking are designated as being able to do so. If you require a statically linkable version of an egg that has not been converted yet, contact the extension author or the CHICKEN mailing list.

Previous: Interface to external functions and variables

Next: Data representation