Use our own Thread struct instead of std::thread

We'd highly prefer using std::thread here; but this won't let us configure the stack
size. macOS uses 512KiB size stacks for non-main threads, and musl defaults to 128k.
While Nix configures a 64MiB size for the main thread, this doesn't propagate to the
threads we launch here. It turns out, running the evaluator under an anemic stack of
0.5MiB has it overflow way too quickly. Hence, we have our own custom Thread struct.

.nix-version

@@ -1 +0,0 @@
-unstable

README.md

@@ -1,5 +1,8 @@
 # nix-eval-jobs
 
+> [!NOTE]
+> This is a fork of nix-eval-jobs that works with Lix.
+
 This project evaluates nix attribute sets in parallel with streamable json
 output. This is useful for time and memory intensive evaluations such as NixOS
 machines, i.e. in a CI context. The evaluation is done with a controllable
@@ -89,11 +92,12 @@ we collect example ci configuration for various CIs.
 
 ## Organisation of this repository
 
-On the `main` branch we target nixUnstable. When a release of nix happens, we
-fork for a release branch i.e. `release-2.8` and change the nix version in
-`.nix-version`. Changes and improvements made in `main` also may be backported
-to these release branches. At the time of writing we only intent to support the
-latest release branch.
+`main` follows Lix HEAD, and is updated alongside the Lix NixOS module. When we
+release we will make a `release-2.90` etc branch, which receives backports.
+
+The version of nix-eval-jobs follows the major version of Lix and minor
+versions of nix-eval-jobs are released as necessary when changes are made in
+n-e-j itself.
 
 ## Projects using nix-eval-jobs
 

default.nix

@@ -11,7 +11,7 @@ let
 in
 stdenv.mkDerivation {
   pname = "nix-eval-jobs";
-  version = "2.19.0";
+  version = "2.90.0-unstable";
   src = if srcDir == null then filterMesonBuild ./. else srcDir;
   buildInputs = with pkgs; [
     nlohmann_json

flake.lock

@@ -23,11 +23,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1701473968,
-        "narHash": "sha256-YcVE5emp1qQ8ieHUnxt1wCZCC3ZfAS+SRRWZ2TMda7E=",
+        "lastModified": 1717285511,
+        "narHash": "sha256-iKzJcpdXih14qYVcZ9QC9XuZYnPc6T8YImb6dX166kw=",
         "owner": "hercules-ci",
         "repo": "flake-parts",
-        "rev": "34fed993f1674c8d06d58b37ce1e0fe5eebcb9f5",
+        "rev": "2a55567fcf15b1b1c7ed712a2c6fadaec7412ea8",
         "type": "github"
       },
       "original": {
@@ -39,6 +39,7 @@
     "lix": {
       "inputs": {
         "flake-compat": "flake-compat",
+        "nix2container": "nix2container",
         "nixpkgs": [
           "nixpkgs"
         ],
@@ -46,11 +47,11 @@
         "pre-commit-hooks": "pre-commit-hooks"
       },
       "locked": {
-        "lastModified": 1717081103,
-        "narHash": "sha256-4hrY8lIK6boX0xe6LN+OFpsmOAITl0Iam17FC8Kjslk=",
+        "lastModified": 1718228457,
+        "narHash": "sha256-vGumESUGu/jo2Lm5bha/xBsJKVlb1wuclXlL9xudRp4=",
         "ref": "refs/heads/main",
-        "rev": "c161687b5fa6e7604e99ee5df2e73388952baafb",
-        "revCount": 15698,
+        "rev": "f46194faa2fc9c78250702c8eb7a4b756e0bd944",
+        "revCount": 15757,
         "type": "git",
         "url": "https://git@git.lix.systems/lix-project/lix"
       },
@@ -66,11 +67,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1701208414,
-        "narHash": "sha256-xrQ0FyhwTZK6BwKhahIkUVZhMNk21IEI1nUcWSONtpo=",
+        "lastModified": 1703863825,
+        "narHash": "sha256-rXwqjtwiGKJheXB43ybM8NwWB8rO2dSRrEqes0S7F5Y=",
         "owner": "nix-community",
         "repo": "nix-github-actions",
-        "rev": "93e39cc1a087d65bcf7a132e75a650c44dd2b734",
+        "rev": "5163432afc817cf8bd1f031418d1869e4c9d5547",
         "type": "github"
       },
       "original": {
@@ -79,18 +80,34 @@
         "type": "github"
       }
     },
+    "nix2container": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1712990762,
+        "narHash": "sha256-hO9W3w7NcnYeX8u8cleHiSpK2YJo7ecarFTUlbybl7k=",
+        "owner": "nlewo",
+        "repo": "nix2container",
+        "rev": "20aad300c925639d5d6cbe30013c8357ce9f2a2e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nlewo",
+        "repo": "nix2container",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1703134684,
-        "narHash": "sha256-SQmng1EnBFLzS7WSRyPM9HgmZP2kLJcPAz+Ug/nug6o=",
+        "lastModified": 1718132686,
+        "narHash": "sha256-JRinkq+FeAkYnrrK8+Bh+jtLHJBN5jDzSimk1ye00EE=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "d6863cbcbbb80e71cecfc03356db1cda38919523",
+        "rev": "96b3dae4f8753c1f5ce0d06b57fe250fb5d9b0e0",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "nixpkgs-unstable",
+        "ref": "nixos-23.11-small",
         "repo": "nixpkgs",
         "type": "github"
       }
@@ -143,11 +160,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1702979157,
-        "narHash": "sha256-RnFBbLbpqtn4AoJGXKevQMCGhra4h6G2MPcuTSZZQ+g=",
+        "lastModified": 1718139168,
+        "narHash": "sha256-1TZQcdETNdJMcfwwoshVeCjwWfrPtkSQ8y8wFX3it7k=",
         "owner": "numtide",
         "repo": "treefmt-nix",
-        "rev": "2961375283668d867e64129c22af532de8e77734",
+        "rev": "1cb529bffa880746a1d0ec4e0f5076876af931f1",
         "type": "github"
       },
       "original": {

flake.nix

@@ -1,7 +1,7 @@
 {
   description = "Hydra's builtin hydra-eval-jobs as a standalone";
 
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11-small";
   inputs.flake-parts.url = "github:hercules-ci/flake-parts";
   inputs.flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
   inputs.treefmt-nix.url = "github:numtide/treefmt-nix";
@@ -17,7 +17,6 @@
     let
       inherit (inputs.nixpkgs) lib;
       inherit (inputs) self;
-      nixVersion = lib.fileContents ./.nix-version;
     in
     flake-parts.lib.mkFlake { inherit inputs; }
       {

src/nix-eval-jobs.cc

@@ -8,6 +8,7 @@
 #include <sys/wait.h>
 #include <nlohmann/json.hpp>
 #include <errno.h>
+#include <pthread.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <string.h>
@@ -24,7 +25,6 @@
 #include <lix/libutil/ref.hh>
 #include <lix/libstore/store-api.hh>
 #include <map>
-#include <thread>
 #include <condition_variable>
 #include <filesystem>
 #include <exception>
@@ -99,6 +99,54 @@ struct Proc {
     ~Proc() {}
 };
 
+// We'd highly prefer using std::thread here; but this won't let us configure the stack
+// size. macOS uses 512KiB size stacks for non-main threads, and musl defaults to 128k.
+// While Nix configures a 64MiB size for the main thread, this doesn't propagate to the
+// threads we launch here. It turns out, running the evaluator under an anemic stack of
+// 0.5MiB has it overflow way too quickly. Hence, we have our own custom Thread struct.
+struct Thread {
+    pthread_t thread;
+
+    Thread(const Thread &) = delete;
+    Thread(Thread &&) noexcept = default;
+
+    Thread(std::function<void(void)> f) {
+        int s;
+        pthread_attr_t attr;
+
+        auto func = std::make_unique<std::function<void(void)>>(std::move(f));
+
+        if ((s = pthread_attr_init(&attr)) != 0) {
+            throw SysError(s, "calling pthread_attr_init");
+        }
+        if ((s = pthread_attr_setstacksize(&attr, 64 * 1024 * 1024)) != 0) {
+            throw SysError(s, "calling pthread_attr_setstacksize");
+        }
+        if ((s = pthread_create(&thread, &attr, Thread::init, func.release())) != 0) {
+            throw SysError(s, "calling pthread_launch");
+        }
+        if ((s = pthread_attr_destroy(&attr)) != 0) {
+            throw SysError(s, "calling pthread_attr_destroy");
+        }
+    }
+
+    void join() {
+        int s;
+        s = pthread_join(thread, nullptr);
+        if (s != 0) {
+            throw SysError(s, "calling pthread_join");
+        }
+    }
+private:
+    static void *init(void *ptr) {
+        std::unique_ptr<std::function<void(void)>> func;
+        func.reset(static_cast<std::function<void(void)> *>(ptr));
+
+        (*func)();
+        return 0;
+    }
+};
+
 struct State {
     std::set<json> todo = json::array({json::array()});
     std::set<json> active;
@@ -332,10 +380,10 @@ int main(int argc, char **argv) {
         Sync<State> state_;
 
         /* Start a collector thread per worker process. */
-        std::vector<std::thread> threads;
+        std::vector<Thread> threads;
         std::condition_variable wakeup;
         for (size_t i = 0; i < myArgs.nrWorkers; i++) {
-            threads.emplace_back(collector, std::ref(state_), std::ref(wakeup));
+            threads.emplace_back(std::bind(collector, std::ref(state_), std::ref(wakeup)));
         }
 
         for (auto &thread : threads)