omnetpp/nixpkgs

Nix packages used by OMNeT++ development environments, for software that nixpkgs does not carry (or does not carry in a usable shape).

Everything here is currently a 3D/geospatial SDK needed by Qtenv's OSG and VSG backends and by the samples/3d-demo simulations.

Using it

{
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/26.05";
  inputs.omnetpp-nixpkgs = {
    url = "github:omnetpp/nixpkgs";
    inputs.nixpkgs.follows = "nixpkgs";   # build against your own nixpkgs
  };

  outputs = { nixpkgs, omnetpp-nixpkgs, ... }:
    let
      system = "x86_64-linux";
      opp = omnetpp-nixpkgs.packages.${system};
    in
    { ... opp.rocky_1_1_0 ... };
}

The follows matters: without it your shell links libraries built against a different nixpkgs than the rest of your environment, which is a live C++ ABI risk. The cost is that you no longer hit a shared binary cache unless your nixpkgs pin matches the one CI builds with.

Build one on its own with:

nix build github:omnetpp/nixpkgs#osgearth_3_8_1

Layout

flake.nix                        version-resolution table + package set
lib/gdal.nix                     shared: GDAL with the darwin installCheck skipped
deps/<name>/<x.y.z>/package.nix  one frozen directory per upstream release

Attribute names are the lowercase package name plus the version with dots replaced by underscores: deps/rocky/1.1.0 is rocky_1_1_0. Only versioned attributes are exported -- there is no unversioned alias, so an existing environment can never be changed by a new release landing here.

package.nix files take their dependencies as bare callPackage arguments with no defaults. Which version is built against which is decided in one place, the let block in flake.nix.

Packages

package	version	why it is here
vsg	1.1.16	nixpkgs has 1.1.15, and static; vsgXchange 1.1.14 needs 1.1.16 and Qtenv links -lvsg
vsgxchange	1.1.14	not in nixpkgs
osgearth	3.8.1	not in nixpkgs
rocky	1.1.0	not in nixpkgs

rocky takes a weejobsNamespace argument. Rocky and osgEarth both vendor the header-only weejobs library in the same jobs namespace at different versions; if both are loaded into one process their weak symbols interpose and a worker thread calls through a vtable of the wrong layout. Set it to move Rocky's copy out of the way:

opp.rocky_1_1_0.override { weejobsNamespace = "rocky_jobs"; }

The default is upstream's jobs, so a consumer that does not use osgEarth gets the package unaltered.

Platforms

x86_64-linux, aarch64-linux and aarch64-darwin. x86_64-darwin is exported too, but does not evaluate: nixpkgs 26.05 marks arrow-cpp broken there and GDAL pulls it in, so osgearth and rocky fail with that error. It is listed so a consumer sees the real upstream reason rather than a missing attribute.

Adding a version

Copy the newest version directory to a new one named after the upstream release, adjust version/hash/patches, and add it to the table in flake.nix. Do not refactor shared code out of the old directory: version directories are frozen on purpose, so that an old one keeps building unchanged. lib/ is the single exception and should stay tiny.