Closure of ldc-built programs is too large

[CyberShadow]

Describe the bug

{ lib, writeText, stdenv, ldc }:
stdenv.mkDerivation {
  name = "ldc-test";
  src = writeText "test.d" ''
    module test;
    import std.stdio;
    void main() {
      writeln("Hello, world!");
    }
  '';
  dontUnpack = true;
  buildInputs = [ ldc ];
  buildPhase = ''
    ldc2 -of=test $src
  '';
  installPhase = ''
    mkdir -p $out/bin
    mv test $out/bin
  '';
}

Building and getting the closure size gives us a number around 1.3 GiB:

$ nix --extra-experimental-features nix-command path-info -S $(nix-build --no-out-link -E '(import <nixpkgs> {}).callPackage ./package.nix {}')
/nix/store/fqlm6ailjq09shqrgrbhf4ll391n5mx8-ldc-test     1395772728

Graph:

It looks like there are some things there which might not need to be there, such as:

• the bootstrap LDC
• LLVM
• considering that the test program was compiled with neither debug information nor is dynamically linked to Phobos, LDC itself

Notify maintainers

CC @ThomasMader @lionello @jtbx

Metadata

• system: "x86_64-linux"
• host os: Linux 6.6.34, NixOS, 24.11 (Vicuna), 24.11pre641786.d603719ec6e2
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.18.2
• nixpkgs: /nix/store/ksj02zhy7qc4dmqi8g2ga8p9hj5173dv-nixpkgs-patched

---

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[lionello]

Also see https://github.com/NixOS/nixpkgs/issues/111475 "dmd keeps references to boostrap compiler" and PR #111525 which had fixes for dmd