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Cross Compilation Adventures with Nim Lang

 ·  โ˜• 6 min read  ·  โœ๏ธ Nishant
Cross Compilation Adventures: Nim Lang

This post is the first in the series Cross Compilation Adventures.

I like working inside the Terminal app. So obviously I am using a lot of Terminal CLI (Command Line Interface) tools ๐Ÿงฐ. To work with these CLI tools, for every usecase there is a small set of shell (bash/zsh) aliases/functions that I have created to work with for specific use cases and to simplify my life. These do differ based on the operating system I am working with (I mostly work with *nix systems i.e macOS and Linux). Remembering these aliases is, let’s just say, not a good developer user experience or DevUX.

For that matter, I have wanted to build my own CLI tools that I could use instead of my shell dependent aliases. Many CLI tools themselves are cross-platform, so my idea is to build cross platform CLI tools for myself.

In order to build such CLI tools, I have been in search of suitable languages to help me build them. For my use case, an ideal language of choice must-have:

  • Ability to generate binaries that are
    • cross-platform: Works on Linux, macOS, Windows (and more if possible).
    • small footprint in size
    • performant (No one wants slow tools ๐Ÿ‘€. Terminal is all about speed ๐Ÿš€)
  • Can cross-compile
    • Binaries for multiple target platform can be built from one platform itself (i.e from macOS compile binaries that run on macOS as well as Linux and Windows platform).
  • Easy to maintain
    • The language is easy and simple enough to pick up. Thus enabling maintaining my project in the long run.

The first langauage that I stumbled upon is Nim Lang.

From the official website:

  • Nim is a statically typed compiled systems programming language. It combines successful concepts from mature languages like Python, Ada and Modula.
  • Nim generates native dependency-free executables, not dependent on a virtual machine, which are small and allow easy redistribution.
  • The Nim compiler and the generated executables support all major platforms like Windows, Linux, BSD and macOS.

Sounds good! Let’s dive into building a very basic CLI tool.

A good example to showcase would be to build a CLI tool that can convert from ยฐC to F and vice versa. Our tool will take an input for value and the unit to be converted to, then output would be converted temprature value.

NOTE: I am using macOS (M2 Pro, Apple Silicon), so the instructions follow through using that only. However the steps should work on all platform with little tweaks.

First we need to install nim-lang. Open your Terminal app and execute the command

curl -sSf | sh

Read here to learn how to install on other platforms

Once installed, you should have access to nim compiler in your Terminal. If not restart your session or open a new Terminal window so it is loaded in the PATH. Follow through next steps

  • Create a file named run.nim.

    touch run.nim
  • Add the below code to the run.nim file and save the file.

    import strutils, std/os
    proc celsiusToFahrenheit(c: float): float =
      result = c * 9 / 5 + 32
    proc fahrenheitToCelsius(f: float): float =
      result = (f - 32) * 5 / 9
    when isMainModule:
      var value: string
      var unit: string
      if paramCount() == 2:
        value = $(paramStr(1).parseFloat())
        unit = paramStr(2).toUpper()
        echo "Usage: ./run <value> <unit_to_convert_to>"
      var convertedTemperature: float
      if unit == "C":
        convertedTemperature = celsiusToFahrenheit(value.parseFloat())
      elif unit == "F":
        convertedTemperature = fahrenheitToCelsius(value.parseFloat())
        echo "Invalid unit. Please use C or F."
      echo "Converted temperature: ", convertedTemperature, "ยฐ", unit

    I am not going to explain this code as it is simple and self explanatory.

    To understand and learn the language I used Learn X in Y minutes: Nim Lang ๐Ÿš€

  • Now to compile, execute the nim compiler with compileargument and the run.nim file:

    nim compile run.nim

    NOTE: You can also replace compile with its shorthand version c in above command.
    i.e nim c run.nim.

    You should now have a binary generated in the same directory with the same name as the nim file i.e run.


    NOTE: I use dust CLI tool to list files in directory with their sizes.
    TIP: You can generate an optimized binary by passing -d:release --opt:size flags at the time of compilation. i.e nim -d:release --opt:size c run.nim. Result is just a smaller binary.

    run optimized

  • Time to execute our generated run binary file:

    โฏ ./run 
    Usage: ./run <value> <unit_to_convert_to>

    Didn’t work ๐Ÿ™„, but we have a helpful message stating how to use the CLI tool ๐Ÿ˜Š

    โฏ ./run 49 C                         
    Converted temperature: 120.2ยฐC

Done! That was a super quick intro to working with Nim Language in less than 5 mins ๐Ÿ˜…

TIP: You can also compile and run the .nim file in one command by using the -r flag along with c flag. i.e nim c -r run.nim

But we aren’t done yet. This generated binary would work on *nix systems. I mentioned earlier that I would like to have cross-(platform + compilation).

nim lang allows to do that easily about which you can read here. Since we already have *nix compatible binary i.e Linux and macOS are sorted for us. We need to cross compile to a format that Windows understands i.e exe/executable. Let’s do that next.

You can read about Windows cross compilation using nim lang here.

  • First install the mingw-w64 toolchain using homebrew for macOS:

    brew install mingw-w64
  • Install MacPorts

  • Start a new Terminal session and install x86_64-w64-mingw32-gcc

    sudo port install x86_64-w64-mingw32-gcc

    NOTE: Due to a path issue, you will have to tell nim where this x86_64-w64-mingw32-gcc is, by editing the nim.cfg file.

    To know the path where x86_64-w64-mingw32-gcc was installed by Macports, run port content x86_64-w64-mingw32-gcc | grep bin/x86_64-w64-mingw32-gcc

    โฏ port content x86_64-w64-mingw32-gcc | grep bin/x86_64-w64-mingw32-gcc

    from above x86_64-w64-mingw32-gcc is installed at path /opt/local/bin. You need to let nim know about this path.

    Open nim.cfg at path ~/.choosenim/toolchains/nim-2.0.0/config/nim.cfg using a code editor i.e VSCode.

    code ~/.choosenim/toolchains/nim-2.0.0/config/nim.cfg

    Find and edit the path value for key under macosx, from /user/bin

    @if macosx: = "/user/bin"

    to /opt/local/bin

    @if macosx: = "/opt/local/bin"

    Save the file and open a new Terminal session.

  • Compile the run.nim file with -d:mingw flag:

    nim c -d:mingw run.nim

    You should now have a .exe binary generated in the same directory with the same name as the nim file i.e run.exe


    TIP: You can generate an optimized binary by passing -d:release --opt:size flags at the time of compilation. i.e nim -d:release --opt:size c -d:mingw run.nim. Result is just a smaller binary.

    run.exe optimized

    NOTE: In order to run this .exe file, you need to either execute this on Windows directly or if on a *nix system then make use of Wine.

TIP: Further reading about reduceing the binary size, read here

Thats it. I think Nim Language pretty much does what I wanted to get out of it:

โœ… Generate cross-platform binaries
โœ… Can cross-compile to platforms
โœ… Easy syntax, so maintainable code

All check boxes ticked is good ๐Ÿ˜Š

BONUS: While my requirement isn’t about compiling to other platforms, but Nim is quite capable such as compiling for Android, iOS and Nintendo-Switch

I’ll be trying this approach of evaluating more languages in the future. You can find the code for this post here.

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Nishant Srivastava
๐Ÿ‘จโ€๐Ÿ’ป Android Engineer/๐Ÿงข Opensource enthusiast

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