Johannes Sasongko’s blog

Posts tagged programming

Saving 1 KiB on Rust executables targetting windows-gnu

While comparing a Rust executable for Windows targetting x86_64-pc-windows-gnu and one targetting x86_64-pc-windows-msvc, I noticed that the -gnu one included an embedded application manifest resource. This particular manifest does two things: setting requestedExecutionLevel to asInvoker, and setting supportedOSes from Windows Vista to Windows 10.

As far as I can tell, the first part attempts to disable the Windows installer detection heuristics. However, the documentation appears to indicate that these heuristics are only used on 32-bit binaries, and the fact that the -msvc executable doesn’t have the manifest reinforces the idea that it’s not needed.

The second part of the manifest is only useful if you want to indicate that you don’t support Windows versions prior to Vista. I think for most people that would be the default assumption these days.

These things considered, it looks to me that removing the manifest shouldn’t cause any issues. The problem is that there doesn’t seem to be any built-in way to do this provided by either the OS or the compiler toolchain. You may have to rely on a third-party tool to do this.

If you don’t mind deleting all embedded resources in the executable—by default there will just be the application manifest—you can use this simple C code (replace file.exe with your executable path): 

#include <windows.h>
int main(void) {
	return 1 - EndUpdateResourceW(BeginUpdateResourceW(L"file.exe", 1), 0);
}

Here’s a slightly more robust but longer Python alternative:

import ctypes
from ctypes import wintypes
import sys

kernel32 = ctypes.windll.kernel32

def check_trueish(result, *_):
	if result:
		return result
	raise ctypes.WinError()

BeginUpdateResource = kernel32.BeginUpdateResourceW
BeginUpdateResource.restype = wintypes.HANDLE
BeginUpdateResource.argtypes = (ctypes.c_wchar_p, wintypes.BOOL)
BeginUpdateResource.errcheck = check_trueish

EndUpdateResource = kernel32.EndUpdateResourceW
EndUpdateResource.restype = wintypes.BOOL
EndUpdateResource.argtypes = (wintypes.HANDLE, wintypes.BOOL)
EndUpdateResource.errcheck = check_trueish

for arg in sys.argv[1:]:
	file_name = ctypes.create_unicode_buffer(arg)
	handle = BeginUpdateResource(file_name, True)
	EndUpdateResource(handle, False)

The slightly bad news here is that, in my testing, removing this manifest only reduces the executable size by exactly 1024 bytes. Considering the x86_64-pc-windows-gnu target generally produces executables in the hundreds of kilobytes at least, this is a fairly inconsequential saving which I probably won’t bother with.

On the search for a Make replacement

Make is great, but there are some issues with it that are probably impossible to fix now. So I’ve been looking for a replacement that I can use for simple task automation; surely in the 40+ years of Make’s lifetime someone has written something better, right?

These are the notes I made while evaluating the different options that I explored. I’m interested to see if anyone has comments, corrections, or other suggestions.

Make

Good old Make. Very nice for all sorts of tasks, until you need to deal with files containing space and/or quote characters, where things start to go downhill.

Ninja

This is only mentioned for completion because Ninja is in a completely different ballpark. It’s meant to be a target language for buildfile generators like CMake and Meson, so by itself it has zero programmability, and you wouldn’t really want to write it by hand.

Just

This feels like a Make variant with fewer features than most Make implementations. I don’t see this as a practical choice for any project, at least right now.

Task

I actually really like the idea of Task. For very simple use cases it’s very elegant, because its whole syntax is just 100% valid YAML with a bit of string templating. The templating sometimes gets in the way, though, because the use of {{.VAR}} for variables conflicts with YAML’s {a: b} map syntax, forcing you to waste one level of string quoting on it.

A bigger flaw is that there’s no easy way to override variables from the command line. I think you can work around this by jumping through scripting hoops, but then you lose a ton of elegance points.

And the biggest flaw: it’s still stringly typed just like Make, so you’ll have trouble separating strings from lists.

Gulp

This looked promising until I noticed that outputs didn’t seem to be tracked anywhere, which means everything gets rebuilt all the time. Is this really the case or am I missing something?

Grunt

Grunt’s documentation is rather bad, and the examples they have all throw you in the deep, ugly end. Skimming these introductory materials, I couldn’t figure out how to write the simplest build file, which seems a bad sign.

Rake

This one looked very promising. I’m not a fan of Ruby, but was willing to put up with it because Rake seemed to do all I wanted. But then I discovered that Ruby’s most reasonable subprocess handler, the shell module, breaks on Windows. Without it, you’re back to various ugly half-baked APIs, each with their own limitations.

SCons and Waf

Two competing Python-based build systems. These seem too complicated for my use cases. I think making them suit simple tasks would be a significant undertaking. Or perhaps I’m just missing a documentation that is not mainly targeted at people trying to create a build pipeline for their C projects.

doit

With this one you end up with lots of boilerplate because rather than writing tasks, you’re writing task creators. It makes sense, but it feels like doing things at a too-low level when you want it to be a simple Make alternative.

The author of doit suggests several high-level interfaces that can be implemented on top of doit. They do limit what you can do, but you can always write normal doit task creators in addition to the simplified versions. I think this is a reasonable compromise and I particularly like the decorator version.

The only remaining problem, then, is that Python’s subprocess handling is very cumbersome. There are two libraries I know of that can rectify this: sh and Plumbum. sh, in my opinion, is not suitable for use in a Make replacement use case. The way it does piping by default is not in line with what we expect, coming from Make. Plumbum is not perfect but better (you still have to end everything with .run_fg() or the magical & FG).

A quirk of doit is that it creates a cache file (or files) alongside your build file. Depending on the exact database backend used, it can create up to three files, which I’d say is not ideal.

Conclusion

I have for now settled on doit + Plumbum with around 100 lines of support code. I’m not fully happy with this, and I’m not sure it can cover all my use cases, but I think it’s time for me to put my ideas and investigations out there and seek comments.

Rake is almost what I need, if not for what I believe is a bug in Ruby’s standard library. But even if it’s fixed, I’d prefer to stick with a Python-based solution if possible.

Transliterating arbitrary text into Latin script

This post explores one of the capabilities of the PyICU library, namely its text transformation module. Specifically, we’ll look at the simplest use case: transliterating text into Latin script.

Say you are given a list of phrases, names, titles, whatever, in a writing system that you’re not familiar with. You want to be able to differentiate the items, but this is hard when you can’t read what they say. Well, let’s turn them into Latin characters (which, assuming you’re reading this in English, you are able to read)! 

>>> import icu
>>> tr = icu.Transliterator.createInstance("Any-Latin; Title").transliterate
>>> tr("Αριστοτέλης, Πλάτων, Σωκράτης")
'Aristotélēs, Plátōn, Sōkrátēs'

There we go. Even though you probably still can’t pronounce these names correctly, at least they’re hopefully easier to recognise because they are now in a script that you are more used to reading (unless you’re Greek, of course).

"Any-Latin; Title" means we want to transliterate from any script to Latin, then convert it to title case. If that’s too simple, the ICU documentation has the gory details of all the supported transforms.

Caveats

As previously aluded to, do not rely on the output as pronunciation guide unless you know what you’re doing. For example, the Korean character 꽃 is transliterated by ICU as kkoch to keep it reversible; that’s not how the word is normally romanised, and if you try to pronounce it like that nobody will understand you.

Another issue is that the transliteration of Han characters (shared between Chinese, Japanese, and Korean) uses Chinese Pinyin, and thus may not resemble the Japanese and Korean romanisations at all. Considering that Japanese writing makes extensive use of these characters, using ICU to transliterate Japanese texts may be a bad idea depending on your use case. 

>>> tr("日本国")  # "Nippon-koku" in Japanese, meaning "Japan"
'Rì Běn Guó'

Oops, that could start an Internet war. Use a different library if you need to properly deal with Japanese text.

Another unfortunate thing with ICU is that there are still scripts that it doesn’t support at all. For example, it can’t transliterate to/from Javanese. 

>>> tr("ꦫꦩꦏꦮꦸꦭꦲꦶꦁꦱ꧀ꦮꦂꦒ")
'ꦫꦩꦏꦮꦸꦭꦲꦶꦁꦱ꧀ꦮꦂꦒ'

Maybe one day.

Using GitLab’s CI server

GitLab provides a continuous integration service, which is pretty nice for building, testing, and packaging your software and having all the UI integrated in GitLab. If you’re just using the free GitLab.com hosting, you get to utilise their Docker-based runner. (If your build process requires a non-Linux OS you’ll have to provide your own runner.)

Getting a basic build up and running is pretty simple. For example, here’s one job named test that only runs make check: 

# .gitlab-ci.yml
test:
  script:
    - make check

If your test suite can measure code coverage, GitLab can also show it in the UI. At the moment this feature is rather rudimentary and requires you to go to the project settings and enter a regular expression to find the coverage amount in the build output.

The following is an example that works with coverage.py when you only have a single Python file. I haven’t tried it with multiple files; it may require a wrapper script that calculates the total coverage amount. 

# .gitlab-ci.yml
test:
  image: python:3-alpine
  script:
    - pip install coverage
    - coverage run foo.py
    - coverage report -m
# Regex that matches the coverage amount:
# ^\S+\.py\s+\d+\s+\d+\s+(\d+\%)

A few lessons learnt from setting up test hooks for a small Python app:

CMake’s ugly programming language

I’ve just discovered Rosetta Code not long ago, and found it quite fun to browse around in. It shows you the code for various programming tasks in different programming languages. While looking at the Quicksort page, I noticed that it didn’t have a CMake version, so I decided to try writing one. 

function (quicksort array_var)
    set (array ${${array_var}})
    if ("${array}" STREQUAL "")
        return ()
    endif ()

    set (less)
    set (equal)
    set (greater)
    list (GET array 0 pivot)

    foreach (x ${array})
        if (x LESS pivot)
            list (APPEND less "${x}")
        elseif (x EQUAL pivot)
            list (APPEND equal "${x}")
        else ()
            list (APPEND greater "${x}")
        endif ()
    endforeach ()

    set (array)
    if (NOT less STREQUAL "")
        quicksort (less)
        list (APPEND array ${less})
    endif ()
    list (APPEND array ${equal})
    if (NOT greater STREQUAL "")
        quicksort (greater)
        list (APPEND array ${greater})
    endif ()
    set ("${array_var}" ${array} PARENT_SCOPE)
endfunction ()

set (a 4 65 2 -31 0 99 83 782 1)
quicksort (a)
message ("${a}")

I’ve worked with CMake for years, and I think it’s a good build system, but I really wish it had switched to a saner language. The CMake language is actually pretty simple and consistent at the syntax level: everything is in the form command(string), where the string syntax is slightly confusing but still rather understandable once you’ve figured out the quoting and variable expansion mechanisms. It’s how that string argument is used that can be messy, inconsistent, and ambiguous. Effectively, it’s as if every command had its own syntax.

Around 2008, there was an experiment to allow writing CMake scripts in Lua. The project never caught on and was abandoned. I think part of the reason was that the thread discussing it in Lua’s mailing list was single-handedly derailed into pointless bickering (which reminds me of the poisonous people talk).

CMake is stuck with a mediocre programming language for the foreseeable future. It’s not as bad as it sounds, though. The simplicity of the syntax has its advantages, and writing CMake buildfiles rarely gets frustrating. It would make a terrible general programming language, but as a build system scripting language it’s workable.