Using gzexe for shipping Racket executables

:: lisp, racket, scheme, tutorial

By: Maciej Barć

Racket executables made by raco exe are known to be quite large. One of tools that can be used to help reduce the size of produced binaries is the gzexe program.

gzeze is a tool that can compress a executable binary. It can be acquired by installing gzip on most Linux distributions (included in the app-arch/gzip package on Gentoo).

Creating a hello-world executable with Racket

Write following contents to hello-world.rkt file:

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#lang racket/base

(define (main)
  (displayln "It REPLs. Ship it!"))

(module+ main
  (main))

To make a binary run:

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raco exe --orig-exe -v -o hello-world hello-world.rkt

The file hello-world will be produced.

This is what file hello-world says about it:

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hello-world: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV),
dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2,
for GNU/Linux 3.2.0, stripped

This “small” executable weights 46 MB!

In comparison busybox weights around 2 MB.

Compressing with gzexe

Keep in mind that gzeze will overwrite the compressed file and create a backup with appended "~".

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gzexe hello-world

And this gives us only 8,5 MB. Nice!

In comparison bazel, which is a single-binary build system written in JAVA, executable takes 33 MB on my Gentoo machine. I tried compressing it with gzexe and it reduces it only by 10%, to around 29 MB.

gzexeis not a silver bullet but with Racket exes it works very nicely.

Genkernel in 2023

:: gentoo, kernel, linux, sysadmin, system, tutorial

By: Maciej Barć

I really wanted to look into the new kernel building solutions for Gentoo and maybe migrate to dracut, but last time I tried, ~1.5 years ago, the initreamfs was now working for me.

And now in 2023 I’m still running genkernel for my personal boxes as well as other servers running Gentoo.

I guess some short term solutions really become defined tools :P

So this is how I rebuild my kernel nowadays:

  1. Copy old config

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    cd /usr/src
    cp linux-6.1.38-gentoo/.config linux-6.1.41-gentoo/
    
  2. Remove old kernel build directories

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    rm -r linux-6.1.31-gentoo
    
  3. Run initial preparation

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    ( eselect kernel set 1 && cd /usr/src/linux && make olddefconfig )
    
  4. Call genkernel

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    genkernel                                                       \
        --no-menuconfig                                             \
        --no-clean                                                  \
        --no-clear-cachedir                                         \
        --no-cleanup                                                \
        --no-mrproper                                               \
        --lvm                                                       \
        --luks                                                      \
        --mdadm                                                     \
        --nfs                                                       \
        --kernel-localversion="-$(hostname)-$(date '+%Y.%m.%d')"    \
        all
    
  5. Rebuild the modules

    If in your /etc/genkernel.conf you have MODULEREBUILD turned off, then also call emerge:

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    emerge -1 @module-rebuild
    

Shell script setup

:: programming, python, shell

By: Maciej Barć

Good practices

Use sh

If you do not need bash features, then use sh, it is installed on every UNIX-like system.

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#!/bin/sh

Exit on failure

Shell scripts continue even if a commend returns error. To fail right away use:

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set -e

Trap C-c

Catch Control-c and exit.

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trap 'exit 128' INT

Use script directory

Assume we are executing a script from directory /Admin, where / is the root of a given project directory.

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script_path="${0}"
script_root="$(dirname "${script_path}")"

We can use ${script_root} to call other scripts form the Admin directory, but we can also use it to relate to the /.

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project_root="$(realpath "${script_root}/../")"
echo "[INFO] Entering directory: ${project_root}"
cd "${project_root}"

So with above we can run commands form / (repository root). Like for example make and other:

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make
python3 ./Admin/serve_1.py

Even better

Use Python for repository maintenance scripts.

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from os import chdir
from os import path

from subprocess import run
from sys import argv

script_path = path.realpath(__file__)
script_root = path.dirname(script_path)
project_root = path.realpath(path.join(script_root, ".."))

print(f" * Entering directory: {project_root}")
chdir(project_root)

leftover_args = argv[1::]
command_arguments = ["make"] + leftover_args

cmd_string = " ".join(command_arguments)
print(f" * Executing command: {cmd_string}")
run(command_arguments, check=True)

ELisp ebuilds good practices

:: elisp, emacs, gentoo, lisp, packaging

By: Maciej Barć

Check load path

Some Elisp package compilation failures are caused by not setting the loadpath correctly. It mostly happens when you compile source from a directory that is not the current working directory. For example:

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elisp-compile elisp/*.el

In most cases you can cd or override the S variable to set it to location where ELisp source resides.

But in other cases you can append to load path the directory with source, see:

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BYTECOMPFLAGS="${BYTECOMPFLAGS} -L elisp" elisp-compile elisp/*.el

Do not rename auto-generated autoload file

elisp-make-autoload-file allows to name the generated autoload file. For sake of easier debugging and writing Gentoo SITEFILEs, please do not rename the generated file.

The name of that file should always be ${PN}-autoloads.el.

Use new elisp-enable-tests function

elisp-enable-tests allows to set up IUSE, RESTRICT, BDEPEND and the test runner function for running tests with the specified test runner.

The 1st (test-runner) argument must be one of:

  • buttercup — for buttercup provided via app-emacs/buttercup,
  • ert-runner — for ert-runner provided via app-emacs/ert-runner,
  • ert — for ERT, the built-in GNU Emacs test utility.

The 2nd argument is the directory where test are located, the leftover arguments are passed to the selected test runner.

Example:

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EAPI=8

inherit elisp

# Other package settings ...

SITEFILE="50${PN}-gentoo.el"
DOCS=( README.md )

elisp-enable-tests buttercup test

Remove empty SITEFILEs

Recently a feature was added to elisp.eclass that will cause build process to generate the required SITEFILE with boilerplate code if it does not exist.

So if your SITEFILE looked like this:

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(add-to-list 'load-path "@SITELISP@")

… then, you can just remove that file.

But remember to keep the SITEFILE variable inside your ebuild:

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SITEFILE="50${PN}-gentoo.el"

Remove pkg.el files

The *-pkg.el files are useless to Gentoo distribution model of Emacs Lisp packages and should be removed. It is as simple as adding this line to a ebuild:

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ELISP_REMOVE="${PN}-pkg.el"

Beware that some packages will try to find their ${PN}-pkg.el file, but in most cases this will show up in failing package tests.

Use official repository

It is tedious to repackage Elpa tarballs, so use the official upstream even if you have to snapshot a specific commit.

To snapshot GitHub repos you would generally use this code:

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# First check if we have the correct version to prevent
# autobumping package version without changing the commit.
[[ ${PV} == *_p20220325 ]] && COMMIT=65c496d3d1d1298345beb9845840067bffb2ffd8

# Use correct URL that supports snapshots.
SRC_URI="https://github.com/domtronn/${PN}/archive/${COMMIT}.tar.gz
    -> ${P}.tar.gz"

# Override the temporary build directory variable.
S="${WORKDIR}"/${PN}-${COMMIT}

Include live version support

We do not want to be worse than the Melpa unstable :D

So, why not allow the given package to be used live?

Even if you do not push the live package to the overlay, please include support for it.

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if [[ ${PV} == *9999* ]] ; then
    inherit git-r3
    EGIT_REPO_URI="https://github.com/example/${PN}.git"
else
    SRC_URI="https://github.com/example/${PN}/archive/${PV}.tar.gz
        -> ${P}.tar.gz"
    KEYWORDS="~amd64 ~x86"
fi

Ask for tags

Git is good, git tags are good. In case if upstream does not tag their package or just forgets to, kindly ask them to create a git tag when bumping Emacs package versions.

Debugging Frog blog with syntax macros

:: blog, language, lisp, macro, programming, racket, scheme, tutorial

By: Maciej Barć

Constructing debugging syntax

I wanted to echo parameter values when I set them in my blog’s frog.rkt config file.

Nothing simpler in Racket!

First I create this macro for echoing a single parameter value when it is set:

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(define-syntax-rule (verbose-set-parameter parameter-id parameter-value)
  (begin
    ;; Set the parameter.
    (parameter-id parameter-value)

    ;; Then call the parameter and print is's value.
    ;; The "'parameter-id" is special syntax
    ;; for turning a "parameter-id" identifier to a symbol.
    ;; We can also write it like:
    ;; > (quote parameter-id)
    ;; to be less confusing.
    (printf "[DEBUG] (~a ~v)\n" 'parameter-id (parameter-id))))

then, I create a wrapper for above macro that can take multiple parameter pairs:

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(define-syntax-rule (verbose-set-parameters (parameter-id parameter-value) ...)
  (begin
    ;; Unpack a chain of "(parameter-id parameter-value)" pairs
    ;; using the "..." syntax.
    (verbose-set-parameter parameter-id parameter-value) ...))

Using the macro

Afterwards we can call it like so:

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(verbose-set-parameters
 (current-title "XGQT's blog")
 (current-author "Maciej Barć"))

Notice that even the form of setting a parameter, that is (parameter-procedure "value"), remains the same, but in reality it is just similar to how the syntax macro pattern-matches on it.

Inspecting macro expansion

In racket-mode inside GNU Emacs we can inspect the macro expansion with racket-expand-region. Stepping through the expansion provided this result:

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(begin
  (begin
    (current-title "XGQT's blog")
    (printf "[DEBUG] (~a ~v)\n" 'current-title (current-title)))
  (begin
    (current-author "Maciej Barć")
    (printf "[DEBUG] (~a ~v)\n" 'current-author (current-author))))