Minor simplification

This makes the header simpler, and silences `hs-bindgen` notices about "squashed" typedefs.

.gitignore

@@ -1,3 +1,4 @@
 dist*
 result
 target
+cabal.project.local*

cabal.project

@@ -1,13 +1,5 @@
 packages: .
 
--- TODO a total hack
-package garnet
-  extra-lib-dirs:
-    /home/gthomas/code/garnet/rust/target/release
-    /home/gthomas/code/garnet/rust/target/debug
-  extra-include-dirs:
-    /home/gthomas/code/garnet/rust
-
 -- https://well-typed.com/blog/2026/02/hs-bindgen-alpha
 -- Haskell.nix doesn't seem to like `tag: release-0.1-alpha`, which the blog post suggests
 -- so we specify the equivalent commit SHAs manually instead

exe/GarnetRs/Wrapped.hs

@@ -6,6 +6,7 @@ module GarnetRs.Wrapped (
     hello,
     helloStruct,
     helloShape,
+    add,
 ) where
 
 import Data.ByteString
@@ -21,15 +22,15 @@ data T = T
     , b :: Word8
     }
 convertT :: T -> Raw.T
-convertT T{a, b} = Raw.T{a = CBool $ fromBool a, b}
+convertT T{a, b} = Raw.T{a = fromBool a, b}
 
 data Shape
     = Circle CDouble
     | Rectangle CDouble CDouble
 convertShape :: Shape -> Raw.Shape
 convertShape = \case
-    Circle r -> Raw.Shape (Raw.Shape_Tag 0) $ Raw.set_shape_body_circle $ Raw.Circle_Body r
+    Circle r -> Raw.Shape Raw.Circle $ Raw.set_shape_body_circle $ Raw.Circle_Body r
-    Rectangle w h -> Raw.Shape (Raw.Shape_Tag 1) $ Raw.set_shape_body_rectangle $ Raw.Rectangle_Body w h
+    Rectangle w h -> Raw.Shape Raw.Rectangle $ Raw.set_shape_body_rectangle $ Raw.Rectangle_Body w h
 
 hello :: ByteString -> IO ()
 hello s = useAsCString s $ Raw.hello . unsafeFromPtr
@@ -39,3 +40,6 @@ helloStruct = Raw.hello_struct . convertT
 
 helloShape :: Shape -> IO ()
 helloShape = Raw.hello_shape . convertShape
+
+add :: Int64 -> Int64 -> Int64
+add = Raw.add

exe/Main.hs

@@ -9,3 +9,4 @@ main = do
     helloStruct T{a = False, b = maxBound}
     helloShape $ Circle 3.14
     helloShape $ Rectangle 10.0 5.0
+    putStrLn $ "3 + 4 = " <> show (add 3 4)

generate-bindings

@@ -5,7 +5,12 @@ set -euo pipefail
 
 # Generate Haskell FFI bindings from Rust source code.
 #
-# Pipeline: cargo build -> cbindgen -> patch header -> hs-bindgen
+# Pipeline:
+#   1. cargo build       - build the Rust static library
+#   2. cbindgen           - generate a C header from the Rust source
+#   3. awk                - patch the header for hs-bindgen compatibility
+#   4. hs-bindgen-cli     - generate Haskell FFI modules from the C header
+#   5. cabal configure    - point Cabal at the Rust build artifacts
 #
 # Prerequisites: run inside the Nix dev shell (provides gcc, cabal, cbindgen, hs-bindgen-cli).
 
@@ -25,59 +30,18 @@ cbindgen \
   --lang c \
   --crate garnet-rs \
   --output "$HEADER" \
+  --style tag \
   "$RUST_DIR"
 
 echo "  Raw header written to $HEADER"
 
 # --- Step 3: Patch the header for hs-bindgen compatibility ---
+#
+# cbindgen emits:    union { ... };       (anonymous)
+# hs-bindgen needs:  union { ... } body;  (named)
+# See: https://github.com/well-typed/hs-bindgen/issues/1649
 echo "=== Patching header ==="
-
-# Two patches are needed:
-#
-# Patch 1: Replace cbindgen's enum pattern with typedef + #defines.
-#   cbindgen emits:  enum Shape_Tag { Circle, Rectangle, }; typedef uint8_t Shape_Tag;
-#   hs-bindgen needs: typedef uint8_t Shape_Tag; #define Circle 0 ...
-#
-# Patch 2: Name anonymous unions inside structs.
-#   cbindgen emits:  union { ... };
-#   hs-bindgen needs: union { ... } body;
-
 awk '
-# State machine for enum->typedef+define transformation
-/^enum [A-Za-z_][A-Za-z0-9_]* \{$/ {
-    in_enum = 1
-    enum_name = $2
-    variant_count = 0
-    delete variants
-    next
-}
-in_enum && /^\};$/ {
-    # Next line should be: typedef <type> <enum_name>;
-    in_enum = 0
-    pending_enum = 1
-    next
-}
-in_enum {
-    # Collect variant names (strip trailing comma and whitespace)
-    v = $0
-    gsub(/^[[:space:]]+/, "", v)
-    gsub(/,[[:space:]]*$/, "", v)
-    if (v != "") {
-        variants[variant_count] = v
-        variant_count++
-    }
-    next
-}
-pending_enum && /^typedef [A-Za-z0-9_]+ / {
-    # Emit: typedef <type> <name>; then #define for each variant
-    print $0
-    for (i = 0; i < variant_count; i++) {
-        printf "#define %s  %d\n", variants[i], i
-    }
-    pending_enum = 0
-    next
-}
-
 # Name anonymous unions: }; at end of union block inside struct -> } body;
 /^  \};$/ && saw_union {
     print "  } body;"
@@ -94,11 +58,11 @@ pending_enum && /^typedef [A-Za-z0-9_]+ / {
 echo "  Patched header at $HEADER"
 
 # --- Step 4: Derive system include paths for hs-bindgen's libclang ---
-echo "=== Detecting system include paths ==="
+#
-
 # hs-bindgen uses libclang directly, which doesn't know about NixOS's
 # non-standard include locations. We extract them from cpp -v and pass
 # all of them — extra paths are harmless.
+echo "=== Detecting system include paths ==="
 CLANG_OPTIONS=()
 while IFS= read -r dir; do
   CLANG_OPTIONS+=("--clang-option" "-isystem$dir")
@@ -122,6 +86,16 @@ hs-bindgen-cli preprocess \
   "${CLANG_OPTIONS[@]}" \
   -I "$RUST_DIR" "$HEADER_NAME"
 
+# --- Step 6: Configure Cabal ---
+#
+# Point Cabal at the Rust static library and C header. This writes
+# cabal.project.local (gitignored) with absolute paths derived from
+# the current working directory, avoiding hardcoded paths in cabal.project.
+echo "=== Configuring Cabal ==="
+cabal configure \
+  --extra-lib-dirs="$RUST_DIR/target/debug" \
+  --extra-include-dirs="$RUST_DIR"
+
 echo "=== Done ==="
 echo "Generated Haskell bindings in $HASKELL_DIR/generated/"
 echo "Run 'cabal run' to test."

generated/GarnetRs.hs

@@ -3,12 +3,12 @@
 {-# LANGUAGE DerivingStrategies #-}
 {-# LANGUAGE DerivingVia #-}
 {-# LANGUAGE DuplicateRecordFields #-}
-{-# LANGUAGE ExplicitForAll #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE MagicHash #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE NoImplicitPrelude #-}
+{-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
@@ -19,8 +19,7 @@
 module GarnetRs where
 
 import qualified Data.Array.Byte
-import qualified Data.Bits as Bits
+import qualified Data.List.NonEmpty
-import qualified Data.Ix as Ix
 import qualified Data.Primitive.Types
 import qualified Data.Proxy
 import qualified Foreign as F
@@ -28,20 +27,20 @@ import qualified Foreign.C as FC
 import qualified GHC.Generics
 import qualified GHC.Ptr as Ptr
 import qualified GHC.Records
+import qualified HsBindgen.Runtime.CEnum
 import qualified HsBindgen.Runtime.HasCField
-import qualified HsBindgen.Runtime.Internal.Bitfield
 import qualified HsBindgen.Runtime.Internal.ByteArray
 import qualified HsBindgen.Runtime.Internal.HasFFIType
 import qualified HsBindgen.Runtime.Internal.SizedByteArray
 import qualified HsBindgen.Runtime.LibC
 import qualified HsBindgen.Runtime.Marshal
-import Data.Bits (FiniteBits)
+import qualified Text.Read
 import HsBindgen.Runtime.Internal.TypeEquality (TyEq)
-import Prelude ((<*>), (>>), Bounded, Enum, Eq, Int, Integral, Num, Ord, Read, Real, Show, pure)
+import Prelude ((<*>), (>>), Eq, Int, Ord, Read, Show, pure, showsPrec)
 
 {-| __C declaration:__ @struct T@
 
-    __defined at:__ @garnet_rs.h 6:16@
+    __defined at:__ @garnet_rs.h 6:8@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -114,34 +113,86 @@ instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType T) "b")
   getField =
     HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"b")
 
-{-| __C declaration:__ @Shape_Tag@
+{-| __C declaration:__ @enum Shape_Tag@
 
-    __defined at:__ @garnet_rs.h 11:17@
+    __defined at:__ @garnet_rs.h 11:6@
 
     __exported by:__ @garnet_rs.h@
 -}
 newtype Shape_Tag = Shape_Tag
-  { unwrap :: HsBindgen.Runtime.LibC.Word8
+  { unwrap :: FC.CUInt
   }
   deriving stock (GHC.Generics.Generic)
-  deriving stock (Eq, Ord, Read, Show)
+  deriving stock (Eq, Ord)
-  deriving newtype
+  deriving newtype (HsBindgen.Runtime.Internal.HasFFIType.HasFFIType)
-    ( HsBindgen.Runtime.Marshal.StaticSize
+
-    , HsBindgen.Runtime.Marshal.ReadRaw
+instance HsBindgen.Runtime.Marshal.StaticSize Shape_Tag where
-    , HsBindgen.Runtime.Marshal.WriteRaw
+
-    , F.Storable
+  staticSizeOf = \_ -> (4 :: Int)
-    , HsBindgen.Runtime.Internal.HasFFIType.HasFFIType
+
-    , Data.Primitive.Types.Prim
+  staticAlignment = \_ -> (4 :: Int)
-    , HsBindgen.Runtime.Internal.Bitfield.Bitfield
+
-    , Bits.Bits
+instance HsBindgen.Runtime.Marshal.ReadRaw Shape_Tag where
-    , Bounded
+
-    , Enum
+  readRaw =
-    , FiniteBits
+    \ptr0 ->
-    , Integral
+          pure Shape_Tag
-    , Ix.Ix
+      <*> HsBindgen.Runtime.Marshal.readRawByteOff ptr0 (0 :: Int)
-    , Num
+
-    , Real
+instance HsBindgen.Runtime.Marshal.WriteRaw Shape_Tag where
-    )
+
+  writeRaw =
+    \ptr0 ->
+      \s1 ->
+        case s1 of
+          Shape_Tag unwrap2 ->
+            HsBindgen.Runtime.Marshal.writeRawByteOff ptr0 (0 :: Int) unwrap2
+
+deriving via HsBindgen.Runtime.Marshal.EquivStorable Shape_Tag instance F.Storable Shape_Tag
+
+deriving via FC.CUInt instance Data.Primitive.Types.Prim Shape_Tag
+
+instance HsBindgen.Runtime.CEnum.CEnum Shape_Tag where
+
+  type CEnumZ Shape_Tag = FC.CUInt
+
+  toCEnum = Shape_Tag
+
+  fromCEnum = GHC.Records.getField @"unwrap"
+
+  declaredValues =
+    \_ ->
+      HsBindgen.Runtime.CEnum.declaredValuesFromList [ (0, Data.List.NonEmpty.singleton "Circle")
+                                                     , (1, Data.List.NonEmpty.singleton "Rectangle")
+                                                     ]
+
+  showsUndeclared =
+    HsBindgen.Runtime.CEnum.showsWrappedUndeclared "Shape_Tag"
+
+  readPrecUndeclared =
+    HsBindgen.Runtime.CEnum.readPrecWrappedUndeclared "Shape_Tag"
+
+  isDeclared = HsBindgen.Runtime.CEnum.seqIsDeclared
+
+  mkDeclared = HsBindgen.Runtime.CEnum.seqMkDeclared
+
+instance HsBindgen.Runtime.CEnum.SequentialCEnum Shape_Tag where
+
+  minDeclaredValue = Circle
+
+  maxDeclaredValue = Rectangle
+
+instance Show Shape_Tag where
+
+  showsPrec = HsBindgen.Runtime.CEnum.shows
+
+instance Read Shape_Tag where
+
+  readPrec = HsBindgen.Runtime.CEnum.readPrec
+
+  readList = Text.Read.readListDefault
+
+  readListPrec = Text.Read.readListPrecDefault
 
 instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Shape_Tag) "unwrap")
          ) => GHC.Records.HasField "unwrap" (Ptr.Ptr Shape_Tag) (Ptr.Ptr ty) where
@@ -151,32 +202,31 @@ instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Shape_Tag) "unwrap")
 
 instance HsBindgen.Runtime.HasCField.HasCField Shape_Tag "unwrap" where
 
-  type CFieldType Shape_Tag "unwrap" =
+  type CFieldType Shape_Tag "unwrap" = FC.CUInt
-    HsBindgen.Runtime.LibC.Word8
 
   offset# = \_ -> \_ -> 0
 
 {-| __C declaration:__ @Circle@
 
-    __defined at:__ @garnet_rs.h 12:9@
+    __defined at:__ @garnet_rs.h 12:3@
 
     __exported by:__ @garnet_rs.h@
 -}
-circle :: FC.CInt
+pattern Circle :: Shape_Tag
-circle = (0 :: FC.CInt)
+pattern Circle = Shape_Tag 0
 
 {-| __C declaration:__ @Rectangle@
 
-    __defined at:__ @garnet_rs.h 13:9@
+    __defined at:__ @garnet_rs.h 13:3@
 
     __exported by:__ @garnet_rs.h@
 -}
-rectangle :: FC.CInt
+pattern Rectangle :: Shape_Tag
-rectangle = (1 :: FC.CInt)
+pattern Rectangle = Shape_Tag 1
 
 {-| __C declaration:__ @struct Circle_Body@
 
-    __defined at:__ @garnet_rs.h 15:16@
+    __defined at:__ @garnet_rs.h 16:8@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -184,7 +234,7 @@ data Circle_Body = Circle_Body
   { radius :: FC.CDouble
     {- ^ __C declaration:__ @radius@
 
-         __defined at:__ @garnet_rs.h 16:10@
+         __defined at:__ @garnet_rs.h 17:10@
 
          __exported by:__ @garnet_rs.h@
     -}
@@ -230,7 +280,7 @@ instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Circle_Body) "radius
 
 {-| __C declaration:__ @struct Rectangle_Body@
 
-    __defined at:__ @garnet_rs.h 19:16@
+    __defined at:__ @garnet_rs.h 20:8@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -238,14 +288,14 @@ data Rectangle_Body = Rectangle_Body
   { width :: FC.CDouble
     {- ^ __C declaration:__ @width@
 
-         __defined at:__ @garnet_rs.h 20:10@
+         __defined at:__ @garnet_rs.h 21:10@
 
          __exported by:__ @garnet_rs.h@
     -}
   , height :: FC.CDouble
     {- ^ __C declaration:__ @height@
 
-         __defined at:__ @garnet_rs.h 21:10@
+         __defined at:__ @garnet_rs.h 22:10@
 
          __exported by:__ @garnet_rs.h@
     -}
@@ -305,7 +355,7 @@ instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Rectangle_Body) "hei
 
 {-| __C declaration:__ @union \@Shape_body@
 
-    __defined at:__ @garnet_rs.h 26:3@
+    __defined at:__ @garnet_rs.h 27:3@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -328,7 +378,7 @@ deriving via HsBindgen.Runtime.Marshal.EquivStorable Shape_body instance F.Stora
 
 __C declaration:__ @circle@
 
-__defined at:__ @garnet_rs.h 27:17@
+__defined at:__ @garnet_rs.h 28:24@
 
 __exported by:__ @garnet_rs.h@
 -}
@@ -355,7 +405,7 @@ set_shape_body_circle =
 
 __C declaration:__ @rectangle@
 
-__defined at:__ @garnet_rs.h 28:20@
+__defined at:__ @garnet_rs.h 29:27@
 
 __exported by:__ @garnet_rs.h@
 -}
@@ -403,7 +453,7 @@ instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Shape_body) "rectang
 
 {-| __C declaration:__ @struct Shape@
 
-    __defined at:__ @garnet_rs.h 24:16@
+    __defined at:__ @garnet_rs.h 25:8@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -411,14 +461,14 @@ data Shape = Shape
   { tag :: Shape_Tag
     {- ^ __C declaration:__ @tag@
 
-         __defined at:__ @garnet_rs.h 25:13@
+         __defined at:__ @garnet_rs.h 26:18@
 
          __exported by:__ @garnet_rs.h@
     -}
   , body :: Shape_body
     {- ^ __C declaration:__ @body@
 
-         __defined at:__ @garnet_rs.h 29:5@
+         __defined at:__ @garnet_rs.h 30:5@
 
          __exported by:__ @garnet_rs.h@
     -}

generated/GarnetRs/FunPtr.hs

@@ -10,6 +10,7 @@ import qualified GHC.IO.Unsafe
 import qualified GHC.Ptr as Ptr
 import qualified HsBindgen.Runtime.Internal.CAPI
 import qualified HsBindgen.Runtime.Internal.HasFFIType
+import qualified HsBindgen.Runtime.LibC
 import qualified HsBindgen.Runtime.PtrConst
 import Data.Void (Void)
 import GarnetRs
@@ -41,6 +42,15 @@ $(HsBindgen.Runtime.Internal.CAPI.addCSource (HsBindgen.Runtime.Internal.CAPI.un
   , "{"
   , "  return &hello_shape;"
   , "}"
+  , "/* com_garnet_GarnetRs_get_add */"
+  , "__attribute__ ((const))"
+  , "int64_t (*hs_bindgen_bbabdbe61cd1eeb2 (void)) ("
+  , "  int64_t arg1,"
+  , "  int64_t arg2"
+  , ")"
+  , "{"
+  , "  return &add;"
+  , "}"
   ]))
 
 -- __unique:__ @com_garnet_GarnetRs_get_hello@
@@ -55,7 +65,7 @@ hs_bindgen_faf62265b53521d3 =
 {-# NOINLINE hello #-}
 {-| __C declaration:__ @hello@
 
-    __defined at:__ @garnet_rs.h 32:6@
+    __defined at:__ @garnet_rs.h 33:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -75,7 +85,7 @@ hs_bindgen_0f8c37ef19b17a6d =
 {-# NOINLINE hello_struct #-}
 {-| __C declaration:__ @hello_struct@
 
-    __defined at:__ @garnet_rs.h 34:6@
+    __defined at:__ @garnet_rs.h 35:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -95,10 +105,30 @@ hs_bindgen_287ff3ac660f333b =
 {-# NOINLINE hello_shape #-}
 {-| __C declaration:__ @hello_shape@
 
-    __defined at:__ @garnet_rs.h 36:6@
+    __defined at:__ @garnet_rs.h 37:6@
 
     __exported by:__ @garnet_rs.h@
 -}
 hello_shape :: Ptr.FunPtr (Shape -> IO ())
 hello_shape =
   GHC.IO.Unsafe.unsafePerformIO hs_bindgen_287ff3ac660f333b
+
+-- __unique:__ @com_garnet_GarnetRs_get_add@
+foreign import ccall unsafe "hs_bindgen_bbabdbe61cd1eeb2" hs_bindgen_bbabdbe61cd1eeb2_base ::
+     IO (Ptr.FunPtr Void)
+
+-- __unique:__ @com_garnet_GarnetRs_get_add@
+hs_bindgen_bbabdbe61cd1eeb2 :: IO (Ptr.FunPtr (HsBindgen.Runtime.LibC.Int64 -> HsBindgen.Runtime.LibC.Int64 -> IO HsBindgen.Runtime.LibC.Int64))
+hs_bindgen_bbabdbe61cd1eeb2 =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_bbabdbe61cd1eeb2_base
+
+{-# NOINLINE add #-}
+{-| __C declaration:__ @add@
+
+    __defined at:__ @garnet_rs.h 39:32@
+
+    __exported by:__ @garnet_rs.h@
+-}
+add :: Ptr.FunPtr (HsBindgen.Runtime.LibC.Int64 -> HsBindgen.Runtime.LibC.Int64 -> IO HsBindgen.Runtime.LibC.Int64)
+add =
+  GHC.IO.Unsafe.unsafePerformIO hs_bindgen_bbabdbe61cd1eeb2

generated/GarnetRs/Safe.hs

@@ -7,9 +7,11 @@ module GarnetRs.Safe where
 
 import qualified Foreign as F
 import qualified Foreign.C as FC
+import qualified GHC.Int
 import qualified GHC.Ptr as Ptr
 import qualified HsBindgen.Runtime.Internal.CAPI
 import qualified HsBindgen.Runtime.Internal.HasFFIType
+import qualified HsBindgen.Runtime.LibC
 import qualified HsBindgen.Runtime.PtrConst
 import Data.Void (Void)
 import GarnetRs
@@ -35,6 +37,13 @@ $(HsBindgen.Runtime.Internal.CAPI.addCSource (HsBindgen.Runtime.Internal.CAPI.un
   , "{"
   , "  hello_shape(*arg1);"
   , "}"
+  , "int64_t hs_bindgen_1c0c71fa74c428a9 ("
+  , "  int64_t arg1,"
+  , "  int64_t arg2"
+  , ")"
+  , "{"
+  , "  return add(arg1, arg2);"
+  , "}"
   ]))
 
 -- __unique:__ @com_garnet_GarnetRs_Safe_hello@
@@ -51,7 +60,7 @@ hs_bindgen_433ea2a26af4e593 =
 
 {-| __C declaration:__ @hello@
 
-    __defined at:__ @garnet_rs.h 32:6@
+    __defined at:__ @garnet_rs.h 33:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -75,7 +84,7 @@ hs_bindgen_51157946af5519c9 =
 
 {-| __C declaration:__ @hello_struct@
 
-    __defined at:__ @garnet_rs.h 34:6@
+    __defined at:__ @garnet_rs.h 35:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -101,7 +110,7 @@ hs_bindgen_7de06f1fd827ca60 =
 
 {-| __C declaration:__ @hello_shape@
 
-    __defined at:__ @garnet_rs.h 36:6@
+    __defined at:__ @garnet_rs.h 37:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -112,3 +121,35 @@ hello_shape ::
 hello_shape =
   \s0 ->
     F.with s0 (\s1 -> hs_bindgen_7de06f1fd827ca60 s1)
+
+-- __unique:__ @com_garnet_GarnetRs_Safe_add@
+foreign import ccall safe "hs_bindgen_1c0c71fa74c428a9" hs_bindgen_1c0c71fa74c428a9_base ::
+     GHC.Int.Int64
+  -> GHC.Int.Int64
+  -> GHC.Int.Int64
+
+-- __unique:__ @com_garnet_GarnetRs_Safe_add@
+hs_bindgen_1c0c71fa74c428a9 ::
+     HsBindgen.Runtime.LibC.Int64
+  -> HsBindgen.Runtime.LibC.Int64
+  -> HsBindgen.Runtime.LibC.Int64
+hs_bindgen_1c0c71fa74c428a9 =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_1c0c71fa74c428a9_base
+
+{-|
+
+  Marked @__attribute((const))__@
+
+__C declaration:__ @add@
+
+__defined at:__ @garnet_rs.h 39:32@
+
+__exported by:__ @garnet_rs.h@
+-}
+add ::
+     HsBindgen.Runtime.LibC.Int64
+     -- ^ __C declaration:__ @a@
+  -> HsBindgen.Runtime.LibC.Int64
+     -- ^ __C declaration:__ @b@
+  -> HsBindgen.Runtime.LibC.Int64
+add = hs_bindgen_1c0c71fa74c428a9

generated/GarnetRs/Unsafe.hs

@@ -7,9 +7,11 @@ module GarnetRs.Unsafe where
 
 import qualified Foreign as F
 import qualified Foreign.C as FC
+import qualified GHC.Int
 import qualified GHC.Ptr as Ptr
 import qualified HsBindgen.Runtime.Internal.CAPI
 import qualified HsBindgen.Runtime.Internal.HasFFIType
+import qualified HsBindgen.Runtime.LibC
 import qualified HsBindgen.Runtime.PtrConst
 import Data.Void (Void)
 import GarnetRs
@@ -35,6 +37,13 @@ $(HsBindgen.Runtime.Internal.CAPI.addCSource (HsBindgen.Runtime.Internal.CAPI.un
   , "{"
   , "  hello_shape(*arg1);"
   , "}"
+  , "int64_t hs_bindgen_20eb651f0a8faf48 ("
+  , "  int64_t arg1,"
+  , "  int64_t arg2"
+  , ")"
+  , "{"
+  , "  return add(arg1, arg2);"
+  , "}"
   ]))
 
 -- __unique:__ @com_garnet_GarnetRs_Unsafe_hello@
@@ -51,7 +60,7 @@ hs_bindgen_2dfe97662a4d6377 =
 
 {-| __C declaration:__ @hello@
 
-    __defined at:__ @garnet_rs.h 32:6@
+    __defined at:__ @garnet_rs.h 33:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -75,7 +84,7 @@ hs_bindgen_29d823ada2bc7302 =
 
 {-| __C declaration:__ @hello_struct@
 
-    __defined at:__ @garnet_rs.h 34:6@
+    __defined at:__ @garnet_rs.h 35:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -101,7 +110,7 @@ hs_bindgen_b3f40a03f07eaa85 =
 
 {-| __C declaration:__ @hello_shape@
 
-    __defined at:__ @garnet_rs.h 36:6@
+    __defined at:__ @garnet_rs.h 37:6@
 
     __exported by:__ @garnet_rs.h@
 -}
@@ -112,3 +121,35 @@ hello_shape ::
 hello_shape =
   \s0 ->
     F.with s0 (\s1 -> hs_bindgen_b3f40a03f07eaa85 s1)
+
+-- __unique:__ @com_garnet_GarnetRs_Unsafe_add@
+foreign import ccall unsafe "hs_bindgen_20eb651f0a8faf48" hs_bindgen_20eb651f0a8faf48_base ::
+     GHC.Int.Int64
+  -> GHC.Int.Int64
+  -> GHC.Int.Int64
+
+-- __unique:__ @com_garnet_GarnetRs_Unsafe_add@
+hs_bindgen_20eb651f0a8faf48 ::
+     HsBindgen.Runtime.LibC.Int64
+  -> HsBindgen.Runtime.LibC.Int64
+  -> HsBindgen.Runtime.LibC.Int64
+hs_bindgen_20eb651f0a8faf48 =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_20eb651f0a8faf48_base
+
+{-|
+
+  Marked @__attribute((const))__@
+
+__C declaration:__ @add@
+
+__defined at:__ @garnet_rs.h 39:32@
+
+__exported by:__ @garnet_rs.h@
+-}
+add ::
+     HsBindgen.Runtime.LibC.Int64
+     -- ^ __C declaration:__ @a@
+  -> HsBindgen.Runtime.LibC.Int64
+     -- ^ __C declaration:__ @b@
+  -> HsBindgen.Runtime.LibC.Int64
+add = hs_bindgen_20eb651f0a8faf48

rust/garnet_rs.h

@@ -3,34 +3,37 @@
 #include <stdint.h>
 #include <stdlib.h>
 
-typedef struct T {
+struct T {
   bool a;
   uint8_t b;
-} T;
+};
 
-typedef uint8_t Shape_Tag;
+enum Shape_Tag {
-#define Circle  0
+  Circle,
-#define Rectangle  1
+  Rectangle,
+};
 
-typedef struct Circle_Body {
+struct Circle_Body {
   double radius;
-} Circle_Body;
+};
 
-typedef struct Rectangle_Body {
+struct Rectangle_Body {
   double width;
   double height;
-} Rectangle_Body;
+};
 
-typedef struct Shape {
+struct Shape {
-  Shape_Tag tag;
+  enum Shape_Tag tag;
   union {
-    Circle_Body circle;
+    struct Circle_Body circle;
-    Rectangle_Body rectangle;
+    struct Rectangle_Body rectangle;
   } body;
-} Shape;
+};
 
 void hello(const char *c);
 
 void hello_struct(struct T t);
 
 void hello_shape(struct Shape s);
+
+__attribute__((const)) int64_t add(int64_t a, int64_t b);

rust/lib.rs

@@ -22,7 +22,7 @@ extern "C" fn hello_struct(t: T) -> () {
     say_hello(&format!("{:?}", t))
 }
 
-#[repr(C, u8)]
+#[repr(C)]
 #[derive(Debug)]
 enum Shape {
     Circle { radius: f64 },
@@ -33,3 +33,9 @@ enum Shape {
 extern "C" fn hello_shape(s: Shape) -> () {
     say_hello(&format!("{:?}", s))
 }
+
+/// cbindgen:prefix=__attribute__((const))
+#[unsafe(no_mangle)]
+extern "C" fn add(a: i64, b: i64) -> i64 {
+    a + b
+}