Merge branch 'main' into Frame-Limited

crates/compiler/alias_analysis/src/lib.rs

@@ -305,8 +305,8 @@ where
                 debug_assert_eq!(variant_types.len(), 1);
                 variant_types[0]
             } else {
-                let data_type = builder.add_union_type(&variant_types)?;
                 let cell_type = builder.add_heap_cell_type();
+                let data_type = builder.add_union_type(&variant_types)?;
 
                 builder.add_tuple_type(&[cell_type, data_type])?
             };
@@ -1476,7 +1476,8 @@ fn expr_spec<'a>(
 
             let _unit = builder.add_update(block, update_mode_var, heap_cell)?;
 
-            with_new_heap_cell(builder, block, union_data)
+            let value = with_new_heap_cell(builder, block, union_data)?;
+            builder.add_make_named(block, MOD_APP, type_name, value)
         }
         RuntimeErrorFunction(_) => {
             let type_id = layout_spec(env, builder, interner, layout)?;

crates/compiler/test_gen/src/gen_primitives.rs

@@ -4421,3 +4421,42 @@ fn layout_cache_structure_with_multiple_recursive_structures() {
         u8
     );
 }
+
+#[test]
+#[cfg(any(feature = "gen-llvm"))]
+fn reset_recursive_type_wraps_in_named_type() {
+    assert_evals_to!(
+        indoc!(
+            r###"
+            app "test" provides [main] to "./platform"
+
+            main : Str
+            main =
+              newList = mapLinkedList (Cons 1 (Cons 2 (Cons 3 Nil))) (\x -> x + 1)
+              printLinkedList newList Num.toStr
+
+            LinkedList a : [Cons a (LinkedList a), Nil]
+
+            mapLinkedList : LinkedList a, (a -> b) -> LinkedList b
+            mapLinkedList = \linkedList, f -> when linkedList is
+              Nil -> Nil
+              Cons x xs ->
+                s = if Bool.true then "true" else "false"
+                expect s == "true"
+
+                Cons (f x) (mapLinkedList xs f)
+
+            printLinkedList : LinkedList a, (a -> Str) -> Str
+            printLinkedList = \linkedList, f ->
+              when linkedList is
+                Nil -> "Nil"
+                Cons x xs ->
+                  strX = f x
+                  strXs = printLinkedList xs f
+                  "Cons \(strX) (\(strXs))"
+            "###
+        ),
+        RocStr::from("Cons 2 (Cons 3 (Cons 4 (Nil)))"),
+        RocStr
+    );
+}

crates/glue/platform/Shape.roc

@@ -132,4 +132,5 @@ RocFn : {
     args : List TypeId,
     lambdaSet : TypeId,
     ret : TypeId,
+    isToplevel : Bool,
 }

crates/glue/platform/Types.roc

@@ -1,5 +1,5 @@
 interface Types
-    exposes [Types, shape, size, alignment, target, walkShapes]
+    exposes [Types, shape, size, alignment, target, walkShapes, entryPoints]
     imports [Shape.{ Shape }, TypeId.{ TypeId }, Target.{ Target }, InternalTypeId]
 
 # TODO: switch AssocList uses to Dict once roc_std is updated.
@@ -19,12 +19,18 @@ Types := {
     ## This is important for declaration order in C; we need to output a
     ## type declaration earlier in the file than where it gets referenced by another type.
     deps : List Tuple2,
+
+    ## Names and types of the entry points of the program (e.g. mainForHost)
+    entrypoints : List Tuple1,
     target : Target,
 }
 
 target : Types -> Target
 target = \@Types types -> types.target
 
+entryPoints : Types -> List Tuple1
+entryPoints = \@Types { entrypoints } -> entrypoints
+
 walkShapes : Types, state, (state, Shape, TypeId -> state) -> state
 walkShapes = \@Types { types: shapes }, originalState, update ->
     List.walk shapes { index: 0, state: originalState } \{ index, state }, elem ->

crates/glue/src/RustGlue.roc

@@ -1,6 +1,6 @@
 app "rust-glue"
     packages { pf: "../platform/main.roc" }
-    imports [pf.Types.{ Types }, pf.File.{ File }, pf.TypeId.{ TypeId }]
+    imports [pf.Types.{ Types }, pf.Shape.{ RocFn }, pf.File.{ File }, pf.TypeId.{ TypeId }]
     provides [makeGlue] to pf
 
 makeGlue : List Types -> Result (List File) Str
@@ -63,9 +63,11 @@ convertTypesToFile = \types ->
                 TagUnion (NonNullableUnwrapped { name, tagName, payload }) ->
                     generateRecursiveTagUnion buf types id name [{ name: tagName, payload: Some payload }] 0 0 None
 
-                Function _ ->
+                Function rocFn ->
-                    # TODO: actually generate glue functions.
+                    if rocFn.isToplevel then
                         buf
+                    else
+                        generateFunction buf types rocFn
 
                 RecursivePointer _ ->
                     # This is recursively pointing to a type that should already have been added,
@@ -92,9 +94,129 @@ convertTypesToFile = \types ->
 
     {
         name: "\(archStr).rs",
-        content,
+        content: content |> generateEntryPoints types,
     }
 
+generateEntryPoints : Str, Types -> Str
+generateEntryPoints = \buf, types ->
+    List.walk (Types.entryPoints types) buf \accum, T name id -> generateEntryPoint accum types name id
+
+generateEntryPoint : Str, Types, Str, TypeId -> Str
+generateEntryPoint = \buf, types, name, id ->
+    publicSignature =
+        when Types.shape types id is
+            Function rocFn ->
+                arguments =
+                    rocFn.args
+                    |> List.mapWithIndex \argId, i ->
+                        type = typeName types argId
+                        c = Num.toStr i
+                        "arg\(c): \(type)"
+                    |> Str.joinWith ", "
+
+                ret = typeName types rocFn.ret
+
+                "(\(arguments)) -> \(ret)"
+
+            _ ->
+                ret = typeName types id
+                "() -> \(ret)"
+
+    externSignature =
+        when Types.shape types id is
+            Function rocFn ->
+                arguments =
+                    rocFn.args
+                    |> List.map \argId ->
+                        type = typeName types argId
+                        "_: \(type)"
+                    |> Str.joinWith ", "
+
+                ret = typeName types rocFn.ret
+                "(_: *mut \(ret), \(arguments))"
+
+            _ ->
+                ret = typeName types id
+                "(_: *mut \(ret))"
+
+    externArguments =
+        when Types.shape types id is
+            Function rocFn ->
+                rocFn.args
+                |> List.mapWithIndex \_, i ->
+                    c = Num.toStr i
+                    "arg\(c)"
+                |> Str.joinWith ", "
+
+            _ ->
+                ""
+
+    """
+    \(buf)
+
+    pub fn \(name)\(publicSignature) {
+        extern "C" {
+            fn roc__\(name)_1_exposed_generic\(externSignature);
+        }
+
+        let mut ret = std::mem::MaybeUninit::uninit();
+
+        unsafe { roc__\(name)_1_exposed_generic(ret.as_mut_ptr(), \(externArguments)) };
+
+        unsafe { ret.assume_init() }
+    }
+    """
+
+generateFunction : Str, Types, RocFn -> Str
+generateFunction = \buf, types, rocFn ->
+    name = rocFn.functionName
+    externName = rocFn.externName
+
+    lambdaSet = typeName types rocFn.lambdaSet
+
+    publicArguments =
+        rocFn.args
+        |> List.mapWithIndex \argId, i ->
+            type = typeName types argId
+            c = Num.toStr i
+            "arg\(c): \(type)"
+        |> Str.joinWith ", "
+
+    externArguments =
+        rocFn.args
+        |> List.mapWithIndex \_, i ->
+            c = Num.toStr i
+            "arg\(c)"
+        |> Str.joinWith ", "
+
+    externComma = if Str.isEmpty publicArguments then "" else ", "
+
+    ret = typeName types rocFn.ret
+
+    """
+    \(buf)
+
+    #[repr(C)]
+    pub struct \(name) {
+        closure_data: \(lambdaSet),
+    }
+
+    impl \(name) {
+        pub fn force_thunk(mut self, \(publicArguments)) -> \(ret) {
+            extern "C" {
+                fn \(externName)(\(publicArguments)\(externComma) closure_data: *mut u8, output: *mut \(ret));
+            }
+
+            let mut output = std::mem::MaybeUninit::uninit();
+            let ptr = &mut self.closure_data as *mut _ as *mut u8;
+
+            unsafe { \(externName)(\(externArguments)\(externComma) ptr, output.as_mut_ptr(), ) };
+
+            unsafe { output.assume_init() }
+        }
+    }
+    """
+
 generateStruct : Str, Types, TypeId, _, _, _ -> Str
 generateStruct = \buf, types, id, name, structFields, visibility ->
     escapedName = escapeKW name
@@ -125,6 +247,7 @@ generateStructFields = \buf, types, visibility, structFields ->
     when structFields is
         HasNoClosure fields ->
             List.walk fields buf (generateStructFieldWithoutClosure types visibility)
+
         HasClosure _ ->
             Str.concat buf "// TODO: Struct fields with closures"
 
@@ -147,6 +270,7 @@ nameTagUnionPayloadFields = \payloadFields ->
         HasNoClosure fields ->
             renamedFields = List.map fields \{ name, id } -> { name: "f\(name)", id }
             HasNoClosure renamedFields
+
         HasClosure fields ->
             renamedFields = List.map fields \{ name, id, accessors } -> { name: "f\(name)", id, accessors }
             HasClosure renamedFields
@@ -371,7 +495,7 @@ generateUnionField = \types ->
                     else
                         typeStr
 
-                Str.concat accum "\(indent)\(escapedFieldName): \(fullTypeStr),\n"
+                Str.concat accum "\(indent)\(escapedFieldName): std::mem::ManuallyDrop<\(fullTypeStr)>,\n"
 
             None ->
                 # If there's no payload, we don't need a discriminant for it.
@@ -417,6 +541,7 @@ generateSingleTagStruct = \buf, types, name, tagName, payload ->
                     generateZeroElementSingleTagStruct b escapedName tagName
                 else
                     generateMultiElementSingleTagStruct b types escapedName tagName fields asStructFields
+
         HasClosure _ ->
             Str.concat buf "\\TODO: SingleTagStruct with closures"
 

crates/glue/src/load.rs

@@ -380,11 +380,8 @@ pub fn load_types(
 
     // Get the variables for all the exposed_to_host symbols
     let variables = (0..decls.len()).filter_map(|index| {
-        if exposed_to_host.contains_key(&decls.symbols[index].value) {
+        let symbol = decls.symbols[index].value;
-            Some(decls.variables[index])
+        exposed_to_host.get(&symbol).copied()
-        } else {
-            None
-        }
     });
 
     let operating_system = target_info.operating_system;
@@ -453,14 +450,14 @@ pub fn load_types(
             }
         }
 
-        let types = Types::new(
+        let types = Types::new_with_entry_points(
             arena,
             subs,
-            variables.clone(),
             arena.alloc(interns),
             glue_procs_by_layout,
             layout_cache,
             target_info,
+            exposed_to_host.clone(),
         );
 
         arch_types.push(types);

crates/glue/src/roc_type/mod.rs

@@ -42,6 +42,7 @@ pub struct File {
 pub struct Types {
     pub aligns: roc_std::RocList<u32>,
     pub deps: roc_std::RocList<Tuple2>,
+    pub entrypoints: roc_std::RocList<Tuple1>,
     pub sizes: roc_std::RocList<u32>,
     pub types: roc_std::RocList<RocType>,
     pub typesByName: roc_std::RocList<Tuple1>,
@@ -567,6 +568,7 @@ pub struct RocFn {
     pub functionName: roc_std::RocStr,
     pub lambdaSet: u32,
     pub ret: u32,
+    pub is_toplevel: bool,
 }
 
 #[cfg(any(target_arch = "aarch64", target_arch = "x86_64"))]
@@ -713,6 +715,7 @@ pub struct RocFn {
     pub functionName: roc_std::RocStr,
     pub lambdaSet: u64,
     pub ret: u64,
+    pub isToplevel: bool,
 }
 
 impl Tuple1 {

crates/glue/src/types.rs

@@ -21,7 +21,7 @@ use roc_mono::{
 };
 use roc_target::{Architecture, OperatingSystem, TargetInfo};
 use roc_types::{
-    subs::{Content, FlatType, GetSubsSlice, Label, Subs, UnionLabels, Variable},
+    subs::{Content, FlatType, GetSubsSlice, Label, Subs, SubsSlice, UnionLabels, Variable},
     types::{AliasKind, RecordField},
 };
 use std::convert::From;
@@ -68,10 +68,16 @@ pub struct Types {
 }
 
 impl Types {
+    const UNIT: TypeId = TypeId(0);
+
     pub fn with_capacity(cap: usize, target_info: TargetInfo) -> Self {
+        let mut types = Vec::with_capacity(cap);
+
+        types.push(RocType::Unit);
+
         Self {
             target: target_info,
-            types: Vec::with_capacity(cap),
+            types,
             types_by_name: FnvHashMap::with_capacity_and_hasher(10, Default::default()),
             entry_points: Vec::new(),
             sizes: Vec::new(),
@@ -81,16 +87,16 @@ impl Types {
     }
 
     #[allow(clippy::too_many_arguments)]
-    pub(crate) fn new<'a, I: Iterator<Item = Variable>>(
+    pub(crate) fn new_with_entry_points<'a>(
         arena: &'a Bump,
         subs: &'a Subs,
-        variables: I,
         interns: &'a Interns,
         glue_procs_by_layout: MutMap<Layout<'a>, &'a [String]>,
         layout_cache: LayoutCache<'a>,
         target: TargetInfo,
+        mut entry_points: MutMap<Symbol, Variable>,
     ) -> Self {
-        let mut types = Self::with_capacity(variables.size_hint().0, target);
+        let mut types = Self::with_capacity(entry_points.len(), target);
         let mut env = Env::new(
             arena,
             subs,
@@ -100,10 +106,23 @@ impl Types {
             target,
         );
 
+        let variables: Vec<_> = entry_points.values().copied().collect();
         for var in variables {
             env.lambda_set_ids = env.find_lambda_sets(var);
-            env.add_type(var, &mut types);
+            let id = env.add_toplevel_type(var, &mut types);
+
+            let key = entry_points
+                .iter()
+                .find_map(|(k, v)| (*v == var).then_some((*k, id)));
+
+            if let Some((k, id)) = key {
+                let name = k.as_str(env.interns).to_string();
+                types.entry_points.push((name, id));
+                entry_points.remove(&k);
             }
+        }
+
+        debug_assert!(entry_points.is_empty());
 
         env.resolve_pending_recursive_types(&mut types);
 
@@ -412,6 +431,7 @@ impl Types {
                     args: args_a,
                     lambda_set: lambda_a,
                     ret: ret_a,
+                    is_toplevel: is_toplevel_a,
                 }),
                 Function(RocFn {
                     function_name: name_b,
@@ -419,12 +439,14 @@ impl Types {
                     args: args_b,
                     lambda_set: lambda_b,
                     ret: ret_b,
+                    is_toplevel: is_toplevel_b,
                 }),
             ) => {
                 // for functions, the name is actually important because two functions
                 // with the same type could have completely different implementations!
                 if name_a == name_b
                     && extern_a == extern_b
+                    && is_toplevel_a == is_toplevel_b
                     && args_a.len() == args_b.len()
                     && self.is_equivalent_help(
                         self.get_type_or_pending(*lambda_a),
@@ -626,9 +648,17 @@ impl From<&Types> for roc_type::Types {
             .iter()
             .map(|(k, v)| roc_type::Tuple1::T(k.as_str().into(), v.0 as _))
             .collect();
+
+        let entrypoints = types
+            .entry_points()
+            .iter()
+            .map(|(k, v)| roc_type::Tuple1::T(k.as_str().into(), v.0 as _))
+            .collect();
+
         roc_type::Types {
             aligns: types.aligns.as_slice().into(),
             deps,
+            entrypoints,
             sizes: types.sizes.as_slice().into(),
             types: types.types.iter().map(|t| t.into()).collect(),
             typesByName: types_by_name,
@@ -667,12 +697,14 @@ impl From<&RocType> for roc_type::RocType {
                 args,
                 lambda_set,
                 ret,
+                is_toplevel,
             }) => roc_type::RocType::Function(roc_type::RocFn {
                 args: args.iter().map(|arg| arg.0 as _).collect(),
                 functionName: function_name.as_str().into(),
                 externName: extern_name.as_str().into(),
                 ret: ret.0 as _,
                 lambdaSet: lambda_set.0 as _,
+                isToplevel: *is_toplevel,
             }),
             RocType::Unit => roc_type::RocType::Unit,
             RocType::Unsized => roc_type::RocType::Unsized,
@@ -937,6 +969,7 @@ impl RocStructFields {
 pub struct RocFn {
     pub function_name: String,
     pub extern_name: String,
+    pub is_toplevel: bool,
     pub args: Vec<TypeId>,
     pub lambda_set: TypeId,
     pub ret: TypeId,
@@ -1261,16 +1294,97 @@ impl<'a> Env<'a> {
         result
     }
 
-    fn add_type(&mut self, var: Variable, types: &mut Types) -> TypeId {
+    fn add_toplevel_type(&mut self, var: Variable, types: &mut Types) -> TypeId {
-        roc_tracing::debug!(content=?roc_types::subs::SubsFmtContent(self.subs.get_content_without_compacting(var), self.subs), "adding type");
+        roc_tracing::debug!(content=?roc_types::subs::SubsFmtContent(self.subs.get_content_without_compacting(var), self.subs), "adding toplevel type");
 
         let layout = self
             .layout_cache
             .from_var(self.arena, var, self.subs)
             .expect("Something weird ended up in the content");
 
-        add_type_help(self, layout, var, None, types)
+        match self.subs.get_content_without_compacting(var) {
+            Content::Structure(FlatType::Func(args, closure_var, ret_var)) => {
+                // this is a toplevel type, so the closure must be empty
+                let is_toplevel = true;
+                add_function_type(
+                    self,
+                    layout,
+                    types,
+                    args,
+                    *closure_var,
+                    *ret_var,
+                    is_toplevel,
+                )
             }
+            _ => add_type_help(self, layout, var, None, types),
+        }
+    }
+}
+
+fn add_function_type<'a>(
+    env: &mut Env<'a>,
+    layout: InLayout<'a>,
+    types: &mut Types,
+    args: &SubsSlice<Variable>,
+    closure_var: Variable,
+    ret_var: Variable,
+    is_toplevel: bool,
+) -> TypeId {
+    let args = env.subs.get_subs_slice(*args);
+    let mut arg_type_ids = Vec::with_capacity(args.len());
+
+    let name = format!("RocFunction_{:?}", closure_var);
+
+    let id = env.lambda_set_ids.get(&closure_var).unwrap();
+    let extern_name = format!("roc__mainForHost_{}_caller", id.0);
+
+    for arg_var in args {
+        let arg_layout = env
+            .layout_cache
+            .from_var(env.arena, *arg_var, env.subs)
+            .expect("Something weird ended up in the content");
+
+        arg_type_ids.push(add_type_help(env, arg_layout, *arg_var, None, types));
+    }
+
+    let lambda_set_type_id = if is_toplevel {
+        Types::UNIT
+    } else {
+        let lambda_set_layout = env
+            .layout_cache
+            .from_var(env.arena, closure_var, env.subs)
+            .expect("Something weird ended up in the content");
+
+        add_type_help(env, lambda_set_layout, closure_var, None, types)
+    };
+
+    let ret_type_id = {
+        let ret_layout = env
+            .layout_cache
+            .from_var(env.arena, ret_var, env.subs)
+            .expect("Something weird ended up in the content");
+
+        add_type_help(env, ret_layout, ret_var, None, types)
+    };
+
+    let fn_type_id = add_function(env, name, types, layout, |name| {
+        RocType::Function(RocFn {
+            function_name: name,
+            extern_name,
+            args: arg_type_ids.clone(),
+            lambda_set: lambda_set_type_id,
+            ret: ret_type_id,
+            is_toplevel,
+        })
+    });
+
+    types.depends(fn_type_id, ret_type_id);
+
+    for arg_type_id in arg_type_ids {
+        types.depends(fn_type_id, arg_type_id);
+    }
+
+    fn_type_id
 }
 
 fn add_type_help<'a>(
@@ -1352,62 +1466,17 @@ fn add_type_help<'a>(
             }
         },
         Content::Structure(FlatType::Func(args, closure_var, ret_var)) => {
-            let args = env.subs.get_subs_slice(*args);
+            let is_toplevel = false; // or in any case, we cannot assume that we are
-            let mut arg_type_ids = Vec::with_capacity(args.len());
 
-            let name = format!("RocFunction_{:?}", closure_var);
+            add_function_type(
-
+                env,
-            let lambda_set_layout = env
+                layout,
-                .layout_cache
+                types,
-                .from_var(env.arena, *closure_var, env.subs)
+                args,
-                .expect("Something weird ended up in the content");
+                *closure_var,
-
+                *ret_var,
-            let _lambda_set = match env.layout_cache.interner.get(lambda_set_layout) {
+                is_toplevel,
-                Layout::LambdaSet(lambda_set) => lambda_set,
+            )
-                _ => unreachable!(),
-            };
-
-            let id = env.lambda_set_ids.get(closure_var).unwrap();
-            let extern_name = format!("roc__mainForHost_{}_caller", id.0);
-
-            for arg_var in args {
-                let arg_layout = env
-                    .layout_cache
-                    .from_var(env.arena, *arg_var, env.subs)
-                    .expect("Something weird ended up in the content");
-
-                arg_type_ids.push(add_type_help(env, arg_layout, *arg_var, None, types));
-            }
-
-            let lambda_set_type_id =
-                add_type_help(env, lambda_set_layout, *closure_var, None, types);
-
-            let ret_type_id = {
-                let ret_layout = env
-                    .layout_cache
-                    .from_var(env.arena, *ret_var, env.subs)
-                    .expect("Something weird ended up in the content");
-
-                add_type_help(env, ret_layout, *ret_var, None, types)
-            };
-
-            let fn_type_id = add_function(env, name, types, layout, |name| {
-                RocType::Function(RocFn {
-                    function_name: name,
-                    extern_name,
-                    args: arg_type_ids.clone(),
-                    lambda_set: lambda_set_type_id,
-                    ret: ret_type_id,
-                })
-            });
-
-            types.depends(fn_type_id, ret_type_id);
-
-            for arg_type_id in arg_type_ids {
-                types.depends(fn_type_id, arg_type_id);
-            }
-
-            fn_type_id
         }
         Content::Structure(FlatType::FunctionOrTagUnion(_, _, _)) => {
             todo!()

crates/glue/tests/fixtures/advanced-recursive-union/app.roc

@@ -6,9 +6,9 @@ app "app"
 main = {
     default: Job {
         command: Command {
-            tool: SystemTool { name: "test", num: 42 }
+            tool: SystemTool { name: "test", num: 42 },
+        },
+        inputFiles: ["foo"],
     },
-        inputFiles : ["foo"]
-    }
 }
 

crates/glue/tests/fixtures/advanced-recursive-union/platform.roc

@@ -7,7 +7,7 @@ platform "test-platform"
 
 Tool : [
     SystemTool { name : Str, num : U32 },
-    FromJob { job : Job, num : U32 }
+    FromJob { job : Job, num : U32 },
 ]
 
 Command : [Command { tool : Tool }]

crates/glue/tests/fixtures/arguments/app.roc

@@ -0,0 +1,7 @@
+app "app"
+    packages { pf: "platform.roc" }
+    imports []
+    provides [main] to pf
+
+main : I64 -> I64
+main = \x -> 2 * x

crates/glue/tests/fixtures/arguments/platform.roc

@@ -0,0 +1,9 @@
+platform "test-platform"
+    requires {} { main : I64 -> I64 }
+    exposes []
+    packages {}
+    imports []
+    provides [mainForHost]
+
+mainForHost : I64 -> I64
+mainForHost = \x -> main x

crates/glue/tests/fixtures/arguments/src/lib.rs

@@ -0,0 +1,60 @@
+mod test_glue;
+
+#[no_mangle]
+pub extern "C" fn rust_main() -> i32 {
+    let answer = test_glue::mainForHost(42i64);
+
+    println!("Answer was: {:?}", answer); // Debug
+
+    // Exit code
+    0
+}
+
+// Externs required by roc_std and by the Roc app
+
+use core::ffi::c_void;
+use std::ffi::CStr;
+use std::os::raw::c_char;
+
+#[no_mangle]
+pub unsafe extern "C" fn roc_alloc(size: usize, _alignment: u32) -> *mut c_void {
+    return libc::malloc(size);
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn roc_realloc(
+    c_ptr: *mut c_void,
+    new_size: usize,
+    _old_size: usize,
+    _alignment: u32,
+) -> *mut c_void {
+    return libc::realloc(c_ptr, new_size);
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn roc_dealloc(c_ptr: *mut c_void, _alignment: u32) {
+    return libc::free(c_ptr);
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
+    match tag_id {
+        0 => {
+            let slice = CStr::from_ptr(c_ptr as *const c_char);
+            let string = slice.to_str().unwrap();
+            eprintln!("Roc hit a panic: {}", string);
+            std::process::exit(1);
+        }
+        _ => todo!(),
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
+    libc::memcpy(dst, src, n)
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
+    libc::memset(dst, c, n)
+}

crates/glue/tests/fixtures/basic-record/src/lib.rs

@@ -1,22 +1,11 @@
 mod test_glue;
 
-extern "C" {
-    #[link_name = "roc__mainForHost_1_exposed_generic"]
-    fn roc_main(_: *mut test_glue::MyRcd);
-}
-
 #[no_mangle]
 pub extern "C" fn rust_main() -> i32 {
     use std::cmp::Ordering;
     use std::collections::hash_set::HashSet;
 
-    let record = unsafe {
+    let record = test_glue::mainForHost();
-        let mut ret: core::mem::MaybeUninit<test_glue::MyRcd> = core::mem::MaybeUninit::uninit();
-
-        roc_main(ret.as_mut_ptr());
-
-        ret.assume_init()
-    };
 
     // Verify that the record has all the expected traits.
 

crates/glue/tests/fixtures/enumeration/src/lib.rs

@@ -1,22 +1,11 @@
 mod test_glue;
 
-extern "C" {
-    #[link_name = "roc__mainForHost_1_exposed_generic"]
-    fn roc_main(_: *mut test_glue::MyEnum);
-}
-
 #[no_mangle]
 pub extern "C" fn rust_main() -> i32 {
     use std::cmp::Ordering;
     use std::collections::hash_set::HashSet;
 
-    let tag_union = unsafe {
+    let tag_union = test_glue::mainForHost();
-        let mut ret: core::mem::MaybeUninit<test_glue::MyEnum> = core::mem::MaybeUninit::uninit();
-
-        roc_main(ret.as_mut_ptr());
-
-        ret.assume_init()
-    };
 
     // Verify that it has all the expected traits.
 

crates/glue/tests/fixtures/list-recursive-union/app.roc

@@ -11,6 +11,6 @@ main = {
         },
         job: [],
         inputFiles: ["foo"],
-    }
+    },
 }
 

crates/glue/tests/fixtures/multiple-modules/src/lib.rs

@@ -1,25 +1,13 @@
 mod test_glue;
 
 use indoc::indoc;
-use test_glue::Combined;
-
-extern "C" {
-    #[link_name = "roc__mainForHost_1_exposed_generic"]
-    fn roc_main(_: *mut Combined);
-}
 
 #[no_mangle]
 pub extern "C" fn rust_main() -> i32 {
     use std::cmp::Ordering;
     use std::collections::hash_set::HashSet;
 
-    let tag_union = unsafe {
+    let tag_union = test_glue::mainForHost();
-        let mut ret: core::mem::MaybeUninit<Combined> = core::mem::MaybeUninit::uninit();
-
-        roc_main(ret.as_mut_ptr());
-
-        ret.assume_init()
-    };
 
     // Verify that it has all the expected traits.
 

crates/glue/tests/fixtures/nested-record/src/lib.rs

@@ -1,21 +1,10 @@
 mod test_glue;
 
-extern "C" {
-    #[link_name = "roc__mainForHost_1_exposed_generic"]
-    fn roc_main(_: *mut test_glue::Outer);
-}
-
 #[no_mangle]
 pub extern "C" fn rust_main() -> i32 {
     use std::cmp::Ordering;
 
-    let outer = unsafe {
+    let outer = test_glue::mainForHost();
-        let mut ret: core::mem::MaybeUninit<test_glue::Outer> = core::mem::MaybeUninit::uninit();
-
-        roc_main(ret.as_mut_ptr());
-
-        ret.assume_init()
-    };
 
     // Verify that `inner` has all the expected traits.
     {

crates/glue/tests/fixtures/single-tag-union/src/lib.rs

@@ -3,23 +3,12 @@ mod test_glue;
 use indoc::indoc;
 use test_glue::SingleTagUnion;
 
-extern "C" {
-    #[link_name = "roc__mainForHost_1_exposed_generic"]
-    fn roc_main(_: *mut SingleTagUnion);
-}
-
 #[no_mangle]
 pub extern "C" fn rust_main() -> i32 {
     use std::cmp::Ordering;
     use std::collections::hash_set::HashSet;
 
-    let tag_union = unsafe {
+    let tag_union = test_glue::mainForHost();
-        let mut ret: core::mem::MaybeUninit<SingleTagUnion> = core::mem::MaybeUninit::uninit();
-
-        roc_main(ret.as_mut_ptr());
-
-        ret.assume_init()
-    };
 
     // Verify that it has all the expected traits.
 

crates/glue/tests/test_glue_cli.rs

@@ -122,6 +122,9 @@ mod glue_cli_run {
         multiple_modules:"multiple-modules" => indoc!(r#"
             combined was: Combined { s1: DepStr1::S("hello"), s2: DepStr2::R("world") }
         "#),
+        arguments:"arguments" => indoc!(r#"
+            Answer was: 84
+        "#),
     }
 
     fn check_for_tests(all_fixtures: &mut roc_collections::VecSet<String>) {

examples/glue/rust-platform/src/lib.rs

@@ -10,10 +10,7 @@ use std::io::Write;
 use std::mem::MaybeUninit;
 use std::os::raw::c_char;
 
-extern "C" {
+use glue::mainForHost as roc_main;
-    #[link_name = "roc__mainForHost_1_exposed_generic"]
-    fn roc_main(_: *mut Op);
-}
 
 #[no_mangle]
 pub unsafe extern "C" fn roc_alloc(size: usize, _alignment: u32) -> *mut c_void {
@@ -93,13 +90,7 @@ pub extern "C" fn rust_main() -> i32 {
 
     println!("Let's do things!");
 
-    let mut op: Op = unsafe {
+    let mut op: Op = roc_main();
-        let mut mem = MaybeUninit::uninit();
-
-        roc_main(mem.as_mut_ptr());
-
-        mem.assume_init()
-    };
 
     loop {
         match dbg!(op.discriminant()) {