| 4 Apr 2026 |
 EsperLily [she/her] | wow i have no idea what's going on but after updating nixpkgs my locally-compiled Vim binary (part of the MacVim package) is crashing during startup. Stepping through with the vim debugger it crashes at func s:StarSetf(ft), and the crash appears to be a bounds check in strcpy. The MacVim package did not change at all, only its inputs changed. I've verified that running the old binary with the new vimrc works fine, and running the new binary with the old vimrc crashes, so it really is a change to the binary compilation. poking at this with nix-diff I see that llvm was updated, also ncurses, also stdenv itself seems to have been updated and bash but it's a little hard to figure out what's actually relevant. I don't suppose there's been any change recently that seems relevant here? | 01:00:22 |
 emily | my guess is something screwy with the weird Xcode/Nixpkgs toolchain mix that ~nothing else does | 01:09:20 |
| emily | either that or LLVM exposing some UB in old Vim code | 01:09:40 |
| emily | (looks like MacVim is lagging behind CVEs again https://github.com/macvim-dev/macvim/issues/1634) | 01:09:50 |
| emily | would probably need bisecting to say for sure what's going on but LLVM update seems like a solid bet | 01:10:26 |
 Randy Eckenrode | What version of LLVM? | 01:14:13 |
| Randy Eckenrode | Some of the earlier 21.1 releases had miscompilation issues on aarch64-darwin. | 01:14:35 |
| Randy Eckenrode | That should be fixed for a while though in Nixpkgs. | 01:14:48 |
 antifuchs | so, I was looking for virtualisation.darwin-builder in the nix-darwin and nixos docs, and neither seems to have that documented. how did you find that? | 01:39:43 |
 Ihar Hrachyshka | $ pwd
/Users/ihrachyshka/src/nixpkgs
$ git grep darwin-builder doc | grep diskSize
doc/packages/darwin-builder.section.md: virtualisation.darwin-builder.diskSize = 5120;
| 01:40:49 |
| antifuchs | Ah, hm, maybe that’s just not in the online nix-darwin manual options list | 01:55:23 |
| Randy Eckenrode | https://github.com/NixOS/nixpkgs/pull/506470 fixes the ICU problem on Darwin. | 02:14:50 |
| EsperLily [she/her] | i'm not 100% positive but i think the MacVim.app/Contents/MacOS/Vim binary is in fact the vim binary produced by the classic vim compilation | 03:22:26 |
| EsperLily [she/her] | the working MacVim was built with llvm-21.1.7, the broken one is built with llvm-21.1.8 | 03:23:26 |
| EsperLily [she/her] | * i'm not 100% positive but i think the MacVim.app/Contents/MacOS/Vim binary is in fact the vim binary produced by the classic vim compilation, meaning without Xcode's involvement | 03:33:19 |
| EsperLily [she/her] | yeah the darwin-builder is actually documented in nixpkgs https://nixos.org/manual/nixpkgs/stable/#sec-darwin-builder-reconfiguring | 03:42:49 |
| EsperLily [she/her] | i just confirmed that if I swap out stdenv.cc with 21.1.7 the crash goes away. I declared a new input nixpkgs-old which is pinned to the older nixpkgs that was working fine and added an overlay ```
(final: prev: {
macvim = prev.macvim.override {
stdenv = final.stdenvAdapters.overrideCC final.stdenv nixpkgs-old.legacyPackages.${system}.stdenv.cc;
};
})
| 04:09:55 |
| EsperLily [she/her] | * i just confirmed that if I swap out stdenv.cc with 21.1.7 the crash goes away. I declared a new input nixpkgs-old which is pinned to the older nixpkgs that was working fine and added an overlay
(final: prev: {
macvim = prev.macvim.override {
stdenv = final.stdenvAdapters.overrideCC final.stdenv nixpkgs-old.legacyPackages.${system}.stdenv.cc;
};
})
| 04:10:12 |
| EsperLily [she/her] | * i just confirmed that if I swap out stdenv.cc with 21.1.7 the crash goes away. I declared a new input nixpkgs-old which is pinned to the older nixpkgs that was working fine and added an overlay
(final: prev: {
macvim = prev.macvim.override {
stdenv = final.stdenvAdapters.overrideCC final.stdenv nixpkgs-old.legacyPackages.${system}.stdenv.cc;
};
})
and this one works without crashing
| 04:10:24 |
| 19 May 2021 |
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