Yesterday, I ran into an issue where two versions of Qt couldn’t run at the same time. This problem has been mentioned by a few people before, with no solutions offered for users. In my case, I was trying to start a nix shell with the rpi-imager. Thankfully, I was able to use the cli, but this was still unexpected and I was under the impression that nix was supposed to fix problems like this.

This is something that Nix cannot fix. Essentially the symbol namespaces in Linux are flat, so if you load two versions of the same library (or two different libraries exposing the symbols even) the first one wins. This is in contrast to eg. Windows where symbols are organized in a tree structure, which has advantages like fewer conflicts, but also comes with disadvantages of its own (eg. it would not be easy to implements something like LD_PRELOAD on such a structure). So on Linux, this is by design / works as intended.

For a bit of background information, you can have a read of github.com/NixOS/nixpkgs/issues/31189

Why is this only an issue on NixOS, then? I can’t find a single instance of this issue on another distro.

Here is the relevant github issue: github.com/NixOS/nixpkgs/issues/37864

Because other distros usually can’t have multiple versions of the same library to begin with.

If these these applications can coexist in other distros, and they can only have one version of Qt, then that means packages in NixOS are overly strict about library versions. I don’t really care what the underlying reason is for this issue, I just know it’s an issue exclusive to NixOS that frustrates me.