How do I go about compiling Erlang from source?

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1

My project uses Elixir (which requires Erlang), and this project uses asdf-vm (or the compatible rtx) to manage the versions.

Erlang is required to be compiled from source in this setup, which happens through kerl, and this is where things go slightly wrong.
I am able to compile erlang, but it seems like OpenSSL is not picked up correctly. After compiling the :crypto application can not be started, and everything points to Erlang not being compiled with OpenSSL.

I’m using the shell.nix to compile it, but honestly I’m just throwing throwing stuff at the wall to see what sticks. Any help is greatly appreciated :slight_smile:

Here is my config:

with import <nixpkgs> { };
let
  # define packages to install
  basePackages = [
    git
    erlang
    elixir
    postgresql # make psql and pg_dump available (e.g. to run mix ecto.dump)
    ### phoenix ###
    libnotify
    inotify-tools
    ### build dependencies - rtx ###
    autoconf
    ncurses
    libxslt
    fop
    wxGTK32
    ### runtime dependencies - rtx ###
    openssl
  ];

  # define shell startup command
  hooks = ''
    export KERL_BUILD_DOCS=yes
    export KERL_INSTALL_HTMLDOCS=no
    export KERL_INSTALL_MANPAGES=no
    #export KERL_CONFIGURE_OPTIONS="--with-ssl=$(which openssl)"
    # this allows mix to work on the local directory
    mkdir -p .nix-mix
    mkdir -p .nix-hex
    export MIX_HOME=$PWD/.nix-mix
    export HEX_HOME=$PWD/.nix-hex
    export PATH=$MIX_HOME/bin:$PATH
    export PATH=$HEX_HOME/bin:$PATH
    export LANG=en_US.UTF-8
    export ERL_AFLAGS="-kernel shell_history enabled"
  '';
in
mkShell {
  buildInputs = basePackages;
  shellHook = hooks;
  # erlang has hardcoded ssl library locations (std_ssl_locations) https://github.com/erlang/otp/blob/4c49b713ddf1830047c55e8a17e3f2255be73462/lib/crypto/configure.ac#L84 
  NIX_LD_LIBRARY_PATH = lib.makeLibraryPath [
    stdenv.cc.cc
    openssl.dev
  ];

  NIX_LD = lib.fileContents "${stdenv.cc}/nix-support/dynamic-linker";
}
2

I never personally was able to make ASDF successfully build me a viable ERTS using only system-level dependencies provided by Nix, so I use the beamPackages that are already part of nixpkgs and (as you yourself already found) I offer some further niceties in shanesveller/nix-beam-flakes to support precise version-pinning to a particular Erlang/Elixir patch-level version.

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