diff --git a/exe/GarnetRs/Wrapped.hs b/exe/GarnetRs/Wrapped.hs
index 504643e..6be065f 100644
--- a/exe/GarnetRs/Wrapped.hs
+++ b/exe/GarnetRs/Wrapped.hs
@@ -6,6 +6,7 @@ module GarnetRs.Wrapped (
     hello,
     helloStruct,
     helloShape,
+    add,
 ) where
 
 import Data.ByteString
@@ -15,6 +16,7 @@ import Foreign.C
 import GarnetRs qualified as Raw
 import GarnetRs.Safe qualified as Raw
 import HsBindgen.Runtime.PtrConst
+import Unsafe.Coerce
 
 data T = T
     { a :: Bool
@@ -39,3 +41,10 @@ helloStruct = Raw.hello_struct . convertT
 
 helloShape :: Shape -> IO ()
 helloShape = Raw.hello_shape . convertShape
+
+add :: Int -> Int -> IO Int
+add a b = from <$> Raw.add (to a) (to b)
+  where
+    -- these types should be the same in practice - both are pointer-sized
+    to = unsafeCoerce @Int @CIntPtr
+    from = unsafeCoerce @CIntPtr @Int
diff --git a/exe/Main.hs b/exe/Main.hs
index 5cd845c..80f3f47 100644
--- a/exe/Main.hs
+++ b/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
diff --git a/generated/GarnetRs/FunPtr.hs b/generated/GarnetRs/FunPtr.hs
index 13f202f..76031fb 100644
--- a/generated/GarnetRs/FunPtr.hs
+++ b/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))"
+  , "intptr_t (*hs_bindgen_bbabdbe61cd1eeb2 (void)) ("
+  , "  intptr_t arg1,"
+  , "  intptr_t arg2"
+  , ")"
+  , "{"
+  , "  return &add;"
+  , "}"
   ]))
 
 -- __unique:__ @com_garnet_GarnetRs_get_hello@
@@ -102,3 +112,23 @@ hs_bindgen_287ff3ac660f333b =
 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.CIntPtr -> HsBindgen.Runtime.LibC.CIntPtr -> IO HsBindgen.Runtime.LibC.CIntPtr))
+hs_bindgen_bbabdbe61cd1eeb2 =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_bbabdbe61cd1eeb2_base
+
+{-# NOINLINE add #-}
+{-| __C declaration:__ @add@
+
+    __defined at:__ @garnet_rs.h 38:10@
+
+    __exported by:__ @garnet_rs.h@
+-}
+add :: Ptr.FunPtr (HsBindgen.Runtime.LibC.CIntPtr -> HsBindgen.Runtime.LibC.CIntPtr -> IO HsBindgen.Runtime.LibC.CIntPtr)
+add =
+  GHC.IO.Unsafe.unsafePerformIO hs_bindgen_bbabdbe61cd1eeb2
diff --git a/generated/GarnetRs/Safe.hs b/generated/GarnetRs/Safe.hs
index 202fdf0..28c2c65 100644
--- a/generated/GarnetRs/Safe.hs
+++ b/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);"
   , "}"
+  , "intptr_t hs_bindgen_1c0c71fa74c428a9 ("
+  , "  intptr_t arg1,"
+  , "  intptr_t arg2"
+  , ")"
+  , "{"
+  , "  return add(arg1, arg2);"
+  , "}"
   ]))
 
 -- __unique:__ @com_garnet_GarnetRs_Safe_hello@
@@ -112,3 +121,31 @@ 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
+  -> IO GHC.Int.Int64
+
+-- __unique:__ @com_garnet_GarnetRs_Safe_add@
+hs_bindgen_1c0c71fa74c428a9 ::
+     HsBindgen.Runtime.LibC.CIntPtr
+  -> HsBindgen.Runtime.LibC.CIntPtr
+  -> IO HsBindgen.Runtime.LibC.CIntPtr
+hs_bindgen_1c0c71fa74c428a9 =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_1c0c71fa74c428a9_base
+
+{-| __C declaration:__ @add@
+
+    __defined at:__ @garnet_rs.h 38:10@
+
+    __exported by:__ @garnet_rs.h@
+-}
+add ::
+     HsBindgen.Runtime.LibC.CIntPtr
+     -- ^ __C declaration:__ @a@
+  -> HsBindgen.Runtime.LibC.CIntPtr
+     -- ^ __C declaration:__ @b@
+  -> IO HsBindgen.Runtime.LibC.CIntPtr
+add = hs_bindgen_1c0c71fa74c428a9
diff --git a/generated/GarnetRs/Unsafe.hs b/generated/GarnetRs/Unsafe.hs
index bc0034d..cea8eee 100644
--- a/generated/GarnetRs/Unsafe.hs
+++ b/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);"
   , "}"
+  , "intptr_t hs_bindgen_20eb651f0a8faf48 ("
+  , "  intptr_t arg1,"
+  , "  intptr_t arg2"
+  , ")"
+  , "{"
+  , "  return add(arg1, arg2);"
+  , "}"
   ]))
 
 -- __unique:__ @com_garnet_GarnetRs_Unsafe_hello@
@@ -112,3 +121,31 @@ 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
+  -> IO GHC.Int.Int64
+
+-- __unique:__ @com_garnet_GarnetRs_Unsafe_add@
+hs_bindgen_20eb651f0a8faf48 ::
+     HsBindgen.Runtime.LibC.CIntPtr
+  -> HsBindgen.Runtime.LibC.CIntPtr
+  -> IO HsBindgen.Runtime.LibC.CIntPtr
+hs_bindgen_20eb651f0a8faf48 =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_20eb651f0a8faf48_base
+
+{-| __C declaration:__ @add@
+
+    __defined at:__ @garnet_rs.h 38:10@
+
+    __exported by:__ @garnet_rs.h@
+-}
+add ::
+     HsBindgen.Runtime.LibC.CIntPtr
+     -- ^ __C declaration:__ @a@
+  -> HsBindgen.Runtime.LibC.CIntPtr
+     -- ^ __C declaration:__ @b@
+  -> IO HsBindgen.Runtime.LibC.CIntPtr
+add = hs_bindgen_20eb651f0a8faf48
diff --git a/rust/garnet_rs.h b/rust/garnet_rs.h
index 92cfeeb..76f3125 100644
--- a/rust/garnet_rs.h
+++ b/rust/garnet_rs.h
@@ -34,3 +34,5 @@ void hello(const char *c);
 void hello_struct(struct T t);
 
 void hello_shape(struct Shape s);
+
+intptr_t add(intptr_t a, intptr_t b);
diff --git a/rust/lib.rs b/rust/lib.rs
index 8db620a..59044e0 100644
--- a/rust/lib.rs
+++ b/rust/lib.rs
@@ -33,3 +33,8 @@ enum Shape {
 extern "C" fn hello_shape(s: Shape) -> () {
     say_hello(&format!("{:?}", s))
 }
+
+#[unsafe(no_mangle)]
+extern "C" fn add(a: isize, b: isize) -> isize {
+    a + b
+}