make it actually work

compiler/build/src/program.rs

@@ -125,7 +125,7 @@ pub fn gen_from_mono_module(
     }
 
     // Uncomment this to see the module's optimized LLVM instruction output:
-    env.module.print_to_stderr();
+    // env.module.print_to_stderr();
 
     mpm.run_on(module);
 

compiler/gen/src/llvm/build.rs

@@ -2158,6 +2158,8 @@ pub fn build_closure_caller<'a, 'ctx, 'env>(
     let context = &env.context;
     let builder = env.builder;
 
+    // STEP 1: build function header
+
     let function_name = format!(
         "{}_{}_caller",
         def_name,
@@ -2215,7 +2217,7 @@ pub fn build_closure_caller<'a, 'ctx, 'env>(
 
     function_value.set_call_conventions(C_CALL_CONV);
 
-    // BUILD FUNCTION BODY
+    // STEP 2: build function body
 
     let entry = context.append_basic_block(function_value, "entry");
 
@@ -2235,18 +2237,36 @@ pub fn build_closure_caller<'a, 'ctx, 'env>(
 
     let result = call.try_as_basic_value().left().unwrap();
 
+    // TODO here we just assume success (first i64 is 0)
     unsafe {
-        let tag_ptr = builder.build_struct_gep(output, 0, "gep");
+        // let tag_ptr = builder.build_struct_gep(output, 0, "gep");
         let result_ptr = builder.build_struct_gep(output, 1, "gep");
 
-        //        let v33 = context.i64_type().const_int(33, false);
-        //        builder.build_store(tag_ptr, v33);
         builder.build_store(result_ptr, result);
     }
 
-    //builder.build_store(output, roc_call_result);
-
     builder.build_return(None);
+
+    // STEP 3: build a {} -> u64 function that gives the size of the return type
+    let size_function_type = env.context.i64_type().fn_type(&[], false);
+    let size_function_name: String = format!(
+        "{}_{}_size",
+        def_name,
+        alias_symbol.ident_string(&env.interns)
+    );
+
+    let size_function = env.module.add_function(
+        size_function_name.as_str(),
+        size_function_type,
+        Some(Linkage::External),
+    );
+
+    let entry = context.append_basic_block(size_function, "entry");
+
+    builder.position_at_end(entry);
+
+    let size: BasicValueEnum = roc_call_result_type.size_of().unwrap().into();
+    builder.build_return(Some(&size));
 }
 
 #[allow(dead_code)]

examples/closure/Closure.roc

@@ -3,6 +3,7 @@ app Closure provides [ makeClosure ] imports []
 makeClosure : ({} -> Int) as MyClosure
 makeClosure = 
     x = 42
+    y = 42
 
-    \{} -> x
+    \{} -> x + y
 

examples/closure/platform/src/lib.rs

@@ -1,6 +1,6 @@
+use roc_std::alloca;
 use std::alloc::Layout;
 use std::ffi::CString;
-use std::mem::MaybeUninit;
 use std::os::raw::c_char;
 use std::time::SystemTime;
 use RocCallResult::*;
@@ -9,40 +9,36 @@ extern "C" {
     #[link_name = "makeClosure_1_exposed"]
     fn make_closure(output: *mut u8) -> ();
 
-    #[link_name = "makeClosure_1_MyClosure_caller"]
-    fn call_MyClosure(
-        unit: (),
-        function_pointer: *const u8,
-        closure_data: *const u8,
-        output: *mut u8,
-    ) -> ();
-
     #[link_name = "makeClosure_1_size"]
     fn closure_size() -> i64;
+
+    #[link_name = "makeClosure_1_MyClosure_caller"]
+    fn call_MyClosure(function_pointer: *const u8, closure_data: *const u8, output: *mut u8) -> ();
+
+    #[link_name = "makeClosure_1_MyClosure_size"]
+    fn size_MyClosure() -> i64;
 }
 
 unsafe fn call_the_closure(function_pointer: *const u8, closure_data_ptr: *const u8) -> i64 {
-    // wow
-    let layout = Layout::array::<u8>(100).unwrap();
-    // let buffer = std::alloc::alloc(layout);
-    let mut foo = (0, 0);
-    let buffer: *mut (i64, i64) = &mut foo;
+    let size = size_MyClosure() as usize;
 
-    call_MyClosure(
-        (),
-        function_pointer,
-        closure_data_ptr as *const u8,
-        buffer as *mut u8,
-    );
+    alloca::with_stack_bytes(size, |buffer| {
+        let buffer: *mut std::ffi::c_void = buffer;
+        let buffer: *mut u8 = buffer as *mut u8;
 
-    dbg!(*buffer);
+        call_MyClosure(
+            function_pointer,
+            closure_data_ptr as *const u8,
+            buffer as *mut u8,
+        );
 
-    let output = &*(buffer as *mut RocCallResult<i64>);
+        let output = &*(buffer as *mut RocCallResult<i64>);
 
-    match output.into() {
-        Ok(v) => v,
-        Err(e) => panic!("failed with {}", e),
-    }
+        match output.into() {
+            Ok(v) => v,
+            Err(e) => panic!("failed with {}", e),
+        }
+    })
 }
 
 #[no_mangle]
@@ -57,12 +53,19 @@ pub fn rust_main() -> isize {
 
         make_closure(buffer);
 
-        let output = &*(buffer as *mut RocCallResult<(*const u8, ())>);
+        let output = &*(buffer as *mut RocCallResult<((), ())>);
 
         match output.into() {
-            Ok((function_pointer, _)) => {
+            Ok((_, _)) => {
+                let function_pointer = {
+                    // this is a pointer to the location where the function pointer is stored
+                    // we pass just the function pointer
+                    let temp = buffer.offset(8) as *const i64;
+
+                    (*temp) as *const u8
+                };
+
                 let closure_data_ptr = buffer.offset(16);
-                dbg!(*closure_data_ptr);
 
                 call_the_closure(function_pointer as *const u8, closure_data_ptr as *const u8)
             }

roc_std/src/alloca.rs

@@ -63,7 +63,8 @@ unsafe fn malloc_or_alloca(bytes: usize) -> *mut c_void {
 #[cfg(not(debug_assertions))]
 #[inline(always)]
 unsafe fn malloc_or_alloca(bytes: usize) -> *mut c_void {
-    c_alloca(bytes)
+    // c_alloca(bytes)
+    libc::malloc(bytes)
 }
 
 #[cfg(debug_assertions)]