Distributing a CFFI wrapper for a custom C lib - common-lisp

I've built a library that wraps custom C code and thinking about the best way to build the shared library as part of the ASDF load. The makefile is conditionalised for various OSs, so it could be as simple as uiop:run-program ..., but I thought I'd ask here if there were a more standard idiom for this.
Because the C code is specific to this application, it won't be available through a package manager and must be built specifically for each users machine. I'm fine with documenting a manual build, but if I can smooth things for the user I will. I notice that Python seems to have some kind of automated way of building libs for their CFFI and wonder if there's something for CL.

For an answer to my own question: there seems to be neither a de-facto way of doing this (based on a search of github asd files), nor a definitive method in the ASDF best practices, though there are some ideas to be gleaned from that document.
I'll put my implementation out as a suggested idiom for this use case, along with some possible alternatives. Hopefully some of the ASDF experts here will correct any misunderstandings.
;; Define a makefile as a type of source file for the system
(defclass makefile (source-file) ((type :initform "m")))
;; tell ASDF how to compile it
(defmethod perform ((o load-op) (c makefile)) t)
(defmethod perform ((o compile-op) (c makefile))
(let* ((lib-dir (system-relative-pathname "cephes" "scipy-cephes"))
(lib (make-pathname :directory `(:relative ,(namestring lib-dir))
:name "libmd"
:type #+unix "so" #+(or windows win32) "dll"))
(built (probe-file (namestring lib))))
(if built
(format *error-output* "Library ~S exists, skipping build" lib)
(format *error-output* "Building ~S~%" lib))
(unless built
(run-program (format nil "cd ~S && make" (namestring lib-dir)) :output t))))
(defsystem "cephes"
:description "Wrapper for the Cephes Mathematical Library"
:version (:read-file-form "version.sexp")
:license "MS-PL"
:depends-on ("cffi")
:serial t
:components ((:module "libmd"
:components ((:makefile "makefile")))
(:file "package")
(:file "init")
(:file "cephes")))
This works fine, on both MS Windows and UNIX. Adding a method to perform seems to be the most common method on github.
An alternative might be to use a build-op, as described in building a system. The description
Some systems offer operations that are neither loading in the current
image, nor testing. Whichever operation a system is meant to be used
with, you may use it with:
(asdf:make :foobar)
This will invoke build-op, which in turn will depend on the
build-operation for the system, if defined, or load-op if not.
Therefore, for usual Lisp systems that want you to load them, the
above will be equivalent to (asdf:load-system :foobar), but for other
Lisp systems, e.g. one that creates a shell command-line executable,
(asdf:make ...) will do the Right Thing™, whatever that Right Thing™
is.
suggest to me that this is rather close to the idea of building a C library, and it would map nicely to the mental model of using a makefile and the asdf:make command. I didn't find too many examples in the wild of this being used though and technically we are loading the C lib into the existing image.
Another point that could be reconsidered is the detection of an existing shared library to avoid the rebuild. make will avoid recompiling if the shared library exists, but will still call the linker again. This causes errors because it can't write to the shared library when it's in use, at least on MS Windows. The ASDF example used Lisp code to detect the existence of the library and avoiding recompilation, but an alternative might be to use output-files.
The ASDF docs are a bit muddled on the purpose of output-files and there are no examples that make their intentions clear, but in the manual section on creating new operations we have:
output-files If your perform method has any output, you must define a
method for this function. for ASDF to determine where the outputs of
performing operation lie.
which suggests that defining the shared library (libmd.so or libmd.dll) is the recommended way to avoid a recompilation if the output-files already exists.
Finally, the C library could be considered a secondary system, cephes/libmd in this case, and added to the :depends-on clause in the main system. The section on other secondary systems demonstrates building an executable this way, with build-op. Except for the fact that this is building an executable and hard-codes ".exe" it seems to map well onto the use case:
To build an executable, define a system as follows (in this case, it's
a secondary system, but it could also be a primary system). You will
be able to create an executable file foobar-command by evaluating
(asdf:make :foobar/executable):
(defsystem "foobar/executable"
:build-operation program-op
:build-pathname "foobar-command" ;; shell name
:entry-point "foobar::start-foobar" ;; thunk
:depends-on ("foobar")
:components ((:file "main")))
The build-pathname gives the name of the executable; a .exe type will
be automatically added on Windows.
I didn't use this method because the secondary system would look almost exactly like the primary one does now, but would be slightly less understandable.

Related

How to permanently save a macro in LISP (sbcl)

Lets say i define a macro
(defmacro foo(x)
(print x))
Now i want to be able to always load this macro in all my lisp files in future where should i save this macro?
Every CL implementation has an init file it calls on start. For SBCL that is ~/.sbclrc. Usually also quicklisp has some setup code in there if you installed quicklisp.
So you could add a line:
(load #P"path/to/your/macro/file.lisp")
And it'll get loaded each time you start SBCL.
You want to have a library.
A library can contain any number of definitions, not only macros.
The de facto standard way to define systems (which is a more general term for libraries, frameworks, and applications — units of software) is to use ASDF.
Let's say that you put your macro into a lisp file:
;;;; my-util.lisp
(in-package cl-user)
(defpackage my-util
(:use cl))
(in-package my-util)
(defmacro foo (x)
`(whatever ,x etc))
Then you put that under a directory that is known to ASDF. One useful directory for that is ~/common-lisp/, so let's use ~/common-lisp/my-util/. In the same directory, put the system definition file:
;;;; my-util.asd
(in-package asdf-user)
(defsystem "my-util"
:components ((:file "my-util")))
Now you can load this utility into any lisp interaction, e. g. on the repl:
CL-USER> (asdf:load-system "my-util")
Or in a different system:
;;;; my-application.asd
(in-package asdf-user)
(defsystem "my-application"
:depends-on ("my-util")
...)
In the case of utility libraries, you often want to use their package so that you don't need to package-qualify the symbols.
If you want things that only work on your computer (like shortcuts for your REPL use or one-off scripts), you can sometimes get away with adding things to your implementation's init file.

What's the meaning of "#+" in the code of cl-mysql? [duplicate]

This question already has answers here:
operator #+ and #- in .sbclrc
(2 answers)
Closed 6 years ago.
Recently I tried to read code about cl-mysql, but got stuck with the #+.
Tried to google it, but not work, so turn to here
(defun make-lock (name)
#+sb-thread (sb-thread:make-mutex :name name)
#+ecl (mp:make-lock :name name)
#+armedbear (ext:make-thread-lock)
#+ (and clisp mt) (mt:make-mutex :name name)
#+allegro (mp:make-process-lock :name name))
And looks like it is for different backend lisp compiler. But still no idea why write something like this.
Anyone can help me make it clear, thx.
#+ is a reader-macro that checks if a keyword is in the special variable *FEATURES*. If it isn't there, the following form will be skipped over (by the reader; the compiler will never see it). There is also #- which does the opposite.
There are some things that aren't part of the Common Lisp standard, but are important enough that all (or most) implementations provide a non-standard extension for them. When you want to use them in code that needs to work on multiple implementations, you have to use read-time conditionals to provide the correct code for the current implementation. Mutexes (and threads in general) are one of those things.
Of course there may be features provided by third party libraries as well. The contents of *FEATURES* will look something like this:
(:SWANK :QUICKLISP :SB-BSD-SOCKETS-ADDRINFO :ASDF-PACKAGE-SYSTEM :ASDF3.1
:ASDF3 :ASDF2 :ASDF :OS-UNIX :NON-BASE-CHARS-EXIST-P :ASDF-UNICODE :64-BIT
:64-BIT-REGISTERS :ALIEN-CALLBACKS :ANSI-CL :ASH-RIGHT-VOPS
:C-STACK-IS-CONTROL-STACK :COMMON-LISP :COMPARE-AND-SWAP-VOPS
:COMPLEX-FLOAT-VOPS :CYCLE-COUNTER :ELF :FLOAT-EQL-VOPS
:FP-AND-PC-STANDARD-SAVE :GENCGC :IEEE-FLOATING-POINT :INLINE-CONSTANTS
:INTEGER-EQL-VOP :INTERLEAVED-RAW-SLOTS :LARGEFILE :LINKAGE-TABLE :LINUX
:LITTLE-ENDIAN :MEMORY-BARRIER-VOPS :MULTIPLY-HIGH-VOPS :OS-PROVIDES-DLADDR
:OS-PROVIDES-DLOPEN :OS-PROVIDES-GETPROTOBY-R :OS-PROVIDES-POLL
:OS-PROVIDES-PUTWC :OS-PROVIDES-SUSECONDS-T :PACKAGE-LOCAL-NICKNAMES
:PRECISE-ARG-COUNT-ERROR :RAW-INSTANCE-INIT-VOPS :SB-DOC :SB-EVAL :SB-FUTEX
:SB-LDB :SB-PACKAGE-LOCKS :SB-SIMD-PACK :SB-SOURCE-LOCATIONS :SB-TEST
:SB-THREAD :SB-UNICODE :SBCL :STACK-ALLOCATABLE-CLOSURES
:STACK-ALLOCATABLE-FIXED-OBJECTS :STACK-ALLOCATABLE-LISTS
:STACK-ALLOCATABLE-VECTORS :STACK-GROWS-DOWNWARD-NOT-UPWARD :SYMBOL-INFO-VOPS
:UNIX :UNWIND-TO-FRAME-AND-CALL-VOP :X86-64)
So if you wanted to write code that depends on Quicklisp for example, you could use #+quicklisp. If you wanted code that is only run if Quicklisp is not available, you'd use #-quicklisp.
You can also use a boolean expression of features. For example,
#+(or sbcl ecl) (format t "Foo!")
would print Foo! on either SBCL or ECL.
#+(and sbcl quicklisp) (format t "Bar!")
would only print Bar! on SBCL that has Quicklisp available.
One could imagine that we can write:
(defun make-lock (name)
(cond ((member :sb-thread *features)
(sb-thread:make-mutex :name name))
((member :ecl *features*)
(mp:make-lock :name name))
...))
But that does usually not work, because we can't read symbols when their package is not existing and some packages are implementation/library/application specific. Packages are not created at read time in a lazy/automatic fashion.
In Common Lisp, reading a symbol of a package, which does not exist, leads to an error:
CL-USER 1 > (read-from-string "foo:bar")
Error: Reader cannot find package FOO.
1 (continue) Create the FOO package.
2 Use another package instead of FOO.
3 Try finding package FOO again.
4 (abort) Return to level 0.
5 Return to top loop level 0.
In your example sb-thread:make-mutex is a symbol which makes sense in SBCL, but not in Allegro CL. Additionally the package SB-THREAD does not exist in Allegro CL. Thus Allegro CL needs to be protected from reading it. In this case, the symbol sb-thread:make-mutex will only be read, if the the feature sb-thread is present on the cl:*features* list. Which is likely only for SBCL, or a Lisp which claims to have sb-threads available.
The feature expressions here prevents the Lisp from trying to read symbols with unknown packages - the packages are unknown, because the respective software is not loaded or not available.

Defining aliases to standard Common Lisp functions?

Lisp is said to enable redefinitions of its core functions.
I want to define an alias to the function cl:documentation function, such that
(doc 'write 'function) === (documentation 'write 'function)
How can this be done and made permanent in SBCL?
Creating an Alias
You are not trying to redefine (i.e., change the definition of) the system function documentation, you want to define your own function with a shorter name which would do the same thing as the system function.
This can be done using fdefinition:
(setf (fdefinition 'doc) #'documentation)
How to make your change "permanent" in common lisp
There is no standard way, different implementation may do it differently, but, generally speaking, there are two common ways.
Add code to an init file - for beginners and casual users
SBCL
CLISP
Clozure
ECL
The code in question will be evaluated anew every time lisp starts.
Pro:
Easy to modify (just edit file)
Takes little disk space
Normal lisp invocation captures the change
Con:
Evaluated every time you start lisp (so, slows start up time if the code is slow)
Save image - for heavy-weight professionals
SBCL
CLISP
Clozure
ECL - not supported
The modified lisp world is saved to disk.
Pro:
Start uptime is unaffected
Con:
Requires re-dumping the world on each change
Lisp image is usually a large file (>10MB)
Must specify the image at invocation time
Even though #sds has already answered pretty thoroughly I just wanted to add that the utility library serapeum has defalias
I use a simple macro for this:
(defmacro alias (to fn)
`(setf (fdefinition ',to) #',fn))
e.g.
(alias neg -) => #<Compiled-function ... >
(neg 10) => -10
Other answers include detail about how to make this permanent.

asdf building and Common Lisp

I am having trouble using the asdf build tools with common lisp. Here is my fractals.asd file:
(defpackage :fractals
(:use :cl :asdf :cl-opengl :cl-glu :cl-glut)
(:export :frac-tree :draw-tree))
(in-package :fractals)
;----------------------------------------------------------
(defsystem fractals
:name "fractals"
:version "0.0.0"
:serial t
:components ((:file "frac-tree")
(:file "fractal-lab")))
Both the ffiles fract-tree.lisp and fractal-lab.lisp have the statement (in-package :fractals) at the very beginning of the file. However, I am automatically getting an error saying The name "CL-OPENGL" does not designate any package. I don't understand why this is wrong. Furthermore, if I don't include these libraries, then I have to manually require them myself... I created a directory called: ~/.config/common-lisp/source-registry.conf.d/ where I placed a file called fractals2.conf which contains the following:
(:directory "~/lisp_proj/fractals2/")
This is the directory of my fractals.asd file as shown above. Apparently, this is supposed to tell asdf where my user-defined systems are located. I followed this tutorial.
In summary, how can I get asdf to find my user-defined systems so that I do not have to manually load them?
Thanks for all the help!
You need to declare your dependencies in the defsystem with a :depends-on clause. The :use clause of the defpackage only makes names of already loaded packages available, but won't load them.
BTW, your .asd file should not include the defpackage of the main package. While it makes sense to declare a special package to run the defsystems in there, regular packages should be declared in .lisp files.
EDIT: This may also solve your second problem. If not, it's probably because ASDF doesn't automatically expand the ~ character in paths. In that case, replace it with the actual path of your home directory.
1- Looks like you were using the undefined fractals:defsystem instead of asdf:defsystem
2- the ASDF DSL accepts the directive (:directory (:home "lisp_proj/fractals_2"))
3- Starting with 3.1.2, you can put everything under ~/common-lisp/
4- For God's Sake, RTFM!

Why can I not access my Leiningen dependencies with Clojure code?

In Clojure, if I want to pull in the clojure.inspector functions, I can go like this:
(use `[clojure.math.numeric-tower :include (expt)])
From the REPL, and I can now evaluate the function expt.
However, it seems to me that there should be (and probably is) another way to do it - pulling in the code using Leiningen dependencies.
I add this line to my project.clj:
[org.clojure/math.numeric-tower "0.0.2"]
And I restart the REPL to pull in the new dependency. I even do "lein deps" to be safe (there is no output for that command). When I try to evaluate expt, it gives me a RuntimeException, and says its Unable to resolve the symbol.
How can I access the expt function, only using Leiningen dependencies?
You can't. It doesn't work like that. Adding a dependency puts the code on your classpath, which merely means it is available for you to use. In order to actually use the things inside the namespaces, you need to use
(require '[the-namespace :refer [the things you want to use]])
or
(require '[the-namespace :as tn])
(tn/somevar)
or do either of those things in an ns declaration (when not in the REPL and working with a file)
(ns foo
(:require [the-namespace :as tn]))

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