hercules-ci · roberth · Nov 21, 2025
diff --git a/flake.lock b/flake.lock
diff --git a/flake.nix b/flake.nix
@@ -5,6 +5,10 @@
   inputs.flake-parts.url = "github:hercules-ci/flake-parts";
   inputs.flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
   inputs.haskell-flake.url = "github:srid/haskell-flake";
+  inputs.hs-bindgen.url = "github:hercules-ci/hs-bindgen/avoid-template-haskell";
+  inputs.hs-bindgen.flake = false;
+  inputs.libclang-bindings.url = "github:well-typed/libclang";
+  inputs.libclang-bindings.flake = false;
 
   # Optional. Omit to use nixpkgs' nix
   # inputs.nix = {
@@ -282,6 +286,16 @@
                   # Slightly faster and does not create deps: source-drv -> inputs
                   defaults.settings.local.impl.buildFromSdist = [ (project.config.basePackages.buildFromCabalSdist) ];
 
+                  # hs-bindgen packages
+                  packages = {
+                    hs-bindgen.source = inputs.hs-bindgen + "/hs-bindgen";
+                    hs-bindgen-runtime.source = inputs.hs-bindgen + "/hs-bindgen-runtime";
+                    c-expr-dsl.source = inputs.hs-bindgen + "/c-expr-dsl";
+                    c-expr-runtime.source = inputs.hs-bindgen + "/c-expr-runtime";
+                    ansi-diff.source = inputs.hs-bindgen + "/ansi-diff";
+                    libclang-bindings.source = inputs.libclang-bindings;
+                  };
+
                   devShell.extraLibraries = hp: {
                     inherit (hp) releaser
                       ascii-progress
@@ -444,6 +458,12 @@
                         (x: x.overrideAttrs (o: {
                           passthru = o.passthru // { nixPackage = nix; };
                         }))
+                        # Add clang/llvm and hs-bindgen for code generation
+                        (h.addBuildTools [
+                          pkgs.llvmPackages.clang
+                          pkgs.llvmPackages.llvm
+                          self.hs-bindgen
+                        ])
                       ];
 
                       # # Dodge build failures of components we don't need.
@@ -468,8 +488,24 @@
                       # releaser = super.callCabal2nix "releaser" (builtins.getFlake "github:hercules-ci/haskell-releaser?rev=e50360ec896fcb6ad724566aece6625973419e8d") { };
 
                       # cabal2nix injects pkg-config dependencies by looking them up in the Haskell package set _or_ `pkgs`
-                      # It does not know about the `nix-flake` pkg-config module yet.
+                      # It does not know about the `nix-flake` and `nix-store-c` pkg-config modules yet.
                       nix-flake = nix;
+                      nix-store-c = nix;
+
+                      # hs-bindgen dependencies that are marked broken in nixpkgs
+                      debruijn = h.dontCheck (h.doJailbreak (h.unmarkBroken super.debruijn));
+                      skew-list = h.dontCheck (h.doJailbreak (h.unmarkBroken super.skew-list));
+
+                      # libclang-bindings needs llvm and libclang - use llvmPackages set
+                      libclang-bindings = h.addExtraLibrary pkgs.llvmPackages.libclang (
+                        h.addBuildTools [ pkgs.llvmPackages.llvm pkgs.llvmPackages.clang ] super.libclang-bindings
+                      );
+
+                      # c-expr-runtime tests require musl headers (see hs-bindgen's own packaging)
+                      c-expr-runtime = h.dontCheck super.c-expr-runtime;
+
+                      # hs-bindgen tests require system headers and have chicken-egg CLI dependency
+                      hs-bindgen = h.dontCheck super.hs-bindgen;
 
                     })
                   ];
@@ -505,6 +541,9 @@
                         pkgs.nixpkgs-fmt
                         pkgs.pre-commit
                         # pkgs.valgrind (broken on x86_64-darwin)
+                        # For hs-bindgen-cli
+                        pkgs.llvmPackages.clang
+                        pkgs.llvmPackages.llvm
                       ] ++ lib.optionals shellWithHaskell [
                         haskellPackages.haskell-language-server
                         pkgs.haskellPackages.implicit-hie # gen-hie

diff --git a/hercules-ci-agent/hercules-ci-agent-worker/Hercules/Agent/Worker/Build/Prefetched.hs b/hercules-ci-agent/hercules-ci-agent-worker/Hercules/Agent/Worker/Build/Prefetched.hs
@@ -45,6 +45,12 @@ C.include "<hercules-ci-cnix/store.hxx>"
 
 C.include "<hercules-ci-cnix/string.hxx>"
 
+-- C API internals header to access C++ Store from C API Store
+C.include "<nix_api_store_internal.h>"
+
+-- Create a typedef to disambiguate C API Store from nix::Store
+C.verbatim "typedef ::Store nix_store;"
+
 C.using "namespace nix"
 
 C.using "namespace hercules_ci_cnix"
@@ -99,9 +105,9 @@ getDerivation (Store store) derivationPath =
   nullableMoveToForeignPtrWrapper
     =<< [C.throwBlock| Derivation *{
       ReceiveInterrupts _;
-      StorePath derivationPath = *$fptr-ptr:(nix::StorePath *derivationPath);
+      nix::StorePath derivationPath = *$fptr-ptr:(nix::StorePath *derivationPath);
       std::list<nix::ref<nix::Store>> stores = getDefaultSubstituters();
-      stores.push_front(*$(refStore* store));
+      stores.push_front($(nix_store* store)->ptr);
 
       nix::Derivation *derivation = nullptr;
 
@@ -135,13 +141,13 @@ buildDerivation (Store store) derivationPath derivation extraInputs =
               alloca $ \errorMessagePtr -> do
                 [C.throwBlock| void {
       ReceiveInterrupts _;
-      Store &store = **$(refStore* store);
+      nix::Store &store = *$(nix_store* store)->ptr;
       bool &success = *$(bool *successPtr);
       int &status = *$(int *statusPtr);
       const char *&errorMessage = *$(const char **errorMessagePtr);
       time_t &startTime = *$(time_t *startTimePtr);
       time_t &stopTime = *$(time_t *stopTimePtr);
-      StorePath derivationPath = *$fptr-ptr:(nix::StorePath *derivationPath);
+      nix::StorePath derivationPath = *$fptr-ptr:(nix::StorePath *derivationPath);
 
       if ($(bool materializeDerivation)) {
         store.addTempRoot(derivationPath);

diff --git a/hercules-ci-agent/hercules-ci-agent-worker/Hercules/Agent/Worker/HerculesStore.hs b/hercules-ci-agent/hercules-ci-agent-worker/Hercules/Agent/Worker/HerculesStore.hs
@@ -38,6 +38,12 @@ C.include "<cstring>"
 
 C.include "hercules-aliases.h"
 
+-- C API internals header to access C++ Store from C API Store
+C.include "<nix_api_store_internal.h>"
+
+-- Create a typedef to disambiguate C API Store from nix::Store
+C.verbatim "typedef ::Store nix_store;"
+
 C.using "namespace nix"
 
 withHerculesStore ::
@@ -48,7 +54,7 @@ withHerculesStore (Store wrappedStore) =
   bracket
     ( liftIO
         [C.block| refHerculesStore* {
-          refStore &s = *$(refStore *wrappedStore);
+          refStore &s = $(nix_store *wrappedStore)->ptr;
           refHerculesStore hs(new HerculesStore(s));
           return new refHerculesStore(hs);
         } |]

diff --git a/hercules-ci-cnix-expr/src/Hercules/CNix/Expr.hs b/hercules-ci-cnix-expr/src/Hercules/CNix/Expr.hs
@@ -120,6 +120,12 @@ C.include "hercules-ci-cnix/expr.hxx"
 
 C.include "hercules-ci-cnix/string.hxx"
 
+-- C API internals header to access C++ Store from C API Store
+C.include "<nix_api_store_internal.h>"
+
+-- Create a typedef to disambiguate C API Store from nix::Store
+C.verbatim "typedef ::Store nix_store;"
+
 C.include "<gc/gc.h>"
 
 C.include "<gc/gc_cpp.h>"
@@ -261,7 +267,7 @@ newEvalState (Store store) =
   liftIO
     [C.throwBlock| EvalState* {
       nix::LookupPath emptyLookupPath;
-      return new EvalState(emptyLookupPath, *$(refStore* store), fetchSettings, evalSettings);
+      return new EvalState(emptyLookupPath, $(nix_store* store)->ptr, fetchSettings, evalSettings);
   } |]
 
 -- | (private) Don't leak it.
@@ -417,12 +423,12 @@ getDrvFile evalState (RawValue v) = liftIO do
       if (!drvInfo)
         throw EvalError(state, "Not a valid derivation");
 
-      StorePath storePath = drvInfo->requireDrvPath();
+      nix::StorePath storePath = drvInfo->requireDrvPath();
 
       // write it (?)
       auto drv = state.store->derivationFromPath(storePath);
 
-      return new StorePath(storePath);
+      return new nix::StorePath(storePath);
     }|]
 
 getAttrBool :: Ptr EvalState -> Value NixAttrs -> ByteString -> IO (Either SomeException (Maybe Bool))

diff --git a/hercules-ci-cnix-store/.gitignore b/hercules-ci-cnix-store/.gitignore
@@ -0,0 +1 @@
+src-generated/
diff --git a/hercules-ci-cnix-store/Setup.hs b/hercules-ci-cnix-store/Setup.hs
@@ -1,13 +1,43 @@
 import Data.Function ((&))
 import Distribution.PkgConfigVersionHook as PV
 import Distribution.Simple
+import Distribution.Simple.LocalBuildInfo
+import Distribution.Simple.Setup
+import Distribution.Simple.Utils
+import Distribution.Verbosity
+import System.Directory (createDirectoryIfMissing)
+import System.Process (callProcess)
 
 main :: IO ()
 main =
   defaultMainWithHooks $
     simpleUserHooks
+      { preBuild = \args flags -> do
+          generateBindings (fromFlag $ buildVerbosity flags)
+          preBuild simpleUserHooks args flags
+      }
       & PV.addHook
         (PV.mkSettings "nix-store")
           { PV.macroName = "NIX",
             PV.flagPrefixName = "nix"
           }
+
+generateBindings :: Verbosity -> IO ()
+generateBindings verbosity = do
+  notice verbosity "Generating Nix C API bindings with hs-bindgen..."
+  createDirectoryIfMissing True "src-generated"
+  callProcess
+    "hs-bindgen-cli"
+    [ "preprocess",
+      "-I",
+      "/nix/store/3bgmbyiinaq8z420gjg8bz2pqf0dpzyp-nix-2.28.5-dev/include",
+      "--hs-output-dir",
+      "src-generated",
+      "--create-output-dirs",
+      "--module",
+      "Hercules.CNix.Nix.API.Store",
+      "--unique-id",
+      "com.hercules-ci.cnix-store",
+      "--enable-program-slicing",
+      "/nix/store/3bgmbyiinaq8z420gjg8bz2pqf0dpzyp-nix-2.28.5-dev/include/nix_api_store.h"
+    ]
diff --git a/hercules-ci-cnix-store/hercules-ci-cnix-store.cabal b/hercules-ci-cnix-store/hercules-ci-cnix-store.cabal
@@ -56,6 +56,8 @@ custom-setup
     base < 5
     , Cabal >= 2.2.0.0 && < 4
     , cabal-pkg-config-version-hook
+    , directory
+    , process
 
 library
   import: cxx-opts
@@ -75,15 +77,26 @@ library
       Hercules.CNix.Store.Instances
       Hercules.CNix.Util
       Hercules.CNix.Verbosity
+  other-modules:
+      Hercules.CNix.Nix.API.Store
+      Hercules.CNix.Nix.API.Store.Safe
+      Hercules.CNix.Nix.API.Store.Unsafe
+      -- Hercules.CNix.Nix.API.Store.FunPtr omitted: uses TH to provide function pointers, which we don't need
+  autogen-modules:
+      Hercules.CNix.Nix.API.Store
+      Hercules.CNix.Nix.API.Store.Safe
+      Hercules.CNix.Nix.API.Store.Unsafe
+      -- Hercules.CNix.Nix.API.Store.FunPtr omitted: uses TH to provide function pointers, which we don't need
   include-dirs:
       include
       cbits
   pkgconfig-depends:
       nix-store >= 2.28 && < 2.31
+    , nix-store-c >= 2.28 && < 2.31
   install-includes:
       hercules-ci-cnix/store.hxx
       hercules-ci-cnix/string.hxx
-  hs-source-dirs: src
+  hs-source-dirs: src src-generated
   cxx-sources:
       cbits/string.cxx
       cbits/signals.cxx
@@ -100,6 +113,8 @@ library
     , unix
     , unliftio-core
     , vector
+    , hs-bindgen-runtime
+    , c-expr-runtime
   if ! flag(ide)
     extra-libraries:
       boost_context