Use simpler tagged union translation

Avoids the worst part of the header hack, and makes Haskell wrapper simpler.
This commit is contained in:
George Thomas 2026-02-19 16:17:29 +00:00
parent 5019af701f
commit 9ca4f615d8
8 changed files with 118 additions and 112 deletions

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@ -29,8 +29,8 @@ data Shape
| 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
Rectangle w h -> Raw.Shape (Raw.Shape_Tag 1) $ Raw.set_shape_body_rectangle $ Raw.Rectangle_Body w h
Circle r -> Raw.Shape Raw.Circle $ Raw.set_shape_body_circle $ Raw.Circle_Body r
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

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@ -36,56 +36,11 @@ echo " Raw header written to $HEADER"
# --- Step 3: Patch the header for hs-bindgen compatibility ---
#
# Two patches are needed, both due to hs-bindgen limitations with cbindgen's
# output for #[repr(C, u8)] tagged enums:
#
# 1. cbindgen emits: enum Shape_Tag { Circle, Rectangle, };
# typedef uint8_t Shape_Tag;
# hs-bindgen needs: typedef uint8_t Shape_Tag;
# #define Circle 0
# #define Rectangle 1
# See: no upstream issue yet for hs-bindgen
#
# 2. cbindgen emits: union { ... }; (anonymous)
# cbindgen emits: union { ... }; (anonymous)
# hs-bindgen needs: union { ... } body; (named)
# See: https://github.com/well-typed/hs-bindgen/issues/1649
echo "=== Patching header ==="
awk '
# State machine for enum->typedef+define transformation
/^enum [A-Za-z_][A-Za-z0-9_]* \{$/ {
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;"

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@ -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.Ix as Ix
import qualified Data.List.NonEmpty
import qualified Data.Primitive.Types
import qualified Data.Proxy
import qualified Foreign as F
@ -28,16 +27,16 @@ 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@
@ -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 11:14@
__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 newtype
( HsBindgen.Runtime.Marshal.StaticSize
, HsBindgen.Runtime.Marshal.ReadRaw
, HsBindgen.Runtime.Marshal.WriteRaw
, F.Storable
, HsBindgen.Runtime.Internal.HasFFIType.HasFFIType
, Data.Primitive.Types.Prim
, HsBindgen.Runtime.Internal.Bitfield.Bitfield
, Bits.Bits
, Bounded
, Enum
, FiniteBits
, Integral
, Ix.Ix
, Num
, Real
)
deriving stock (Eq, Ord)
deriving newtype (HsBindgen.Runtime.Internal.HasFFIType.HasFFIType)
instance HsBindgen.Runtime.Marshal.StaticSize Shape_Tag where
staticSizeOf = \_ -> (4 :: Int)
staticAlignment = \_ -> (4 :: Int)
instance HsBindgen.Runtime.Marshal.ReadRaw Shape_Tag where
readRaw =
\ptr0 ->
pure Shape_Tag
<*> HsBindgen.Runtime.Marshal.readRawByteOff ptr0 (0 :: Int)
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" =
HsBindgen.Runtime.LibC.Word8
type CFieldType Shape_Tag "unwrap" = FC.CUInt
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
circle = (0 :: FC.CInt)
pattern Circle :: Shape_Tag
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
rectangle = (1 :: FC.CInt)
pattern Rectangle :: Shape_Tag
pattern Rectangle = Shape_Tag 1
{-| __C declaration:__ @struct Circle_Body@
__defined at:__ @garnet_rs.h 15:16@
__defined at:__ @garnet_rs.h 16:16@
__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 20:16@
__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 28:17@
__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 29:20@
__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 25:16@
__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 26:13@
__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@
-}

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@ -65,7 +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@
-}
@ -85,7 +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@
-}
@ -105,7 +105,7 @@ 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@
-}
@ -125,7 +125,7 @@ hs_bindgen_bbabdbe61cd1eeb2 =
{-# NOINLINE add #-}
{-| __C declaration:__ @add@
__defined at:__ @garnet_rs.h 38:32@
__defined at:__ @garnet_rs.h 39:32@
__exported by:__ @garnet_rs.h@
-}

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@ -60,7 +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@
-}
@ -84,7 +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@
-}
@ -110,7 +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@
-}
@ -142,7 +142,7 @@ hs_bindgen_1c0c71fa74c428a9 =
__C declaration:__ @add@
__defined at:__ @garnet_rs.h 38:32@
__defined at:__ @garnet_rs.h 39:32@
__exported by:__ @garnet_rs.h@
-}

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@ -60,7 +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@
-}
@ -84,7 +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@
-}
@ -110,7 +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@
-}
@ -142,7 +142,7 @@ hs_bindgen_20eb651f0a8faf48 =
__C declaration:__ @add@
__defined at:__ @garnet_rs.h 38:32@
__defined at:__ @garnet_rs.h 39:32@
__exported by:__ @garnet_rs.h@
-}

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@ -8,9 +8,10 @@ typedef struct T {
uint8_t b;
} T;
typedef uint8_t Shape_Tag;
#define Circle 0
#define Rectangle 1
typedef enum Shape_Tag {
Circle,
Rectangle,
} Shape_Tag;
typedef struct Circle_Body {
double radius;

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@ -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 },