use RocCallResult and pass-by-reference in all examples

compiler/gen/src/llvm/build.rs

@@ -1960,9 +1960,15 @@ fn make_exception_catching_wrapper<'a, 'ctx, 'env>(
     let result_alloca = builder.build_alloca(wrapper_return_type, "result");
 
     // invoke instead of call, so that we can catch any exeptions thrown in Roc code
+    let arguments = wrapper_function.get_params();
     let call_result = {
-        let call =
-            builder.build_invoke(roc_function, &[], then_block, catch_block, "call_roc_main");
+        let call = builder.build_invoke(
+            roc_function,
+            &arguments,
+            then_block,
+            catch_block,
+            "call_roc_function",
+        );
         call.set_call_convention(FAST_CALL_CONV);
         call.try_as_basic_value().left().unwrap()
     };

examples/closure/Closure.roc

@@ -4,5 +4,5 @@ closure : {} -> Int
 closure = 
     x = 42
 
-    \{} -> x
+    \{} -> x + 9223372036854775807
 

examples/hello-world/platform/src/lib.rs

@@ -2,7 +2,7 @@ use roc_std::RocStr;
 use std::str;
 
 extern "C" {
-    #[link_name = "main_1"]
+    #[link_name = "main_1_exposed"]
     fn main() -> RocStr;
 }
 

examples/multi-module/platform/src/lib.rs

@@ -1,9 +1,10 @@
+use roc_std::RocCallResult;
 use roc_std::RocList;
 use std::time::SystemTime;
 
 extern "C" {
-    #[link_name = "quicksort_1"]
-    fn quicksort(list: RocList<i64>) -> RocList<i64>;
+    #[link_name = "quicksort_1_exposed"]
+    fn quicksort(list: RocList<i64>, output: &mut RocCallResult<RocList<i64>>) -> ();
 }
 
 const NUM_NUMS: usize = 100;
@@ -24,7 +25,17 @@ pub fn rust_main() -> isize {
 
     println!("Running Roc quicksort on {} numbers...", nums.len());
     let start_time = SystemTime::now();
-    let answer = unsafe { quicksort(nums) };
+    let answer = unsafe {
+        use std::mem::MaybeUninit;
+        let mut output = MaybeUninit::uninit();
+
+        quicksort(nums, &mut *output.as_mut_ptr());
+
+        match output.assume_init().into() {
+            Ok(value) => value,
+            Err(msg) => panic!("roc failed with message: {}", msg),
+        }
+    };
     let end_time = SystemTime::now();
     let duration = end_time.duration_since(start_time).unwrap();
 

examples/quicksort/platform/src/lib.rs

@@ -2,7 +2,7 @@ use roc_std::RocList;
 use std::time::SystemTime;
 
 extern "C" {
-    #[link_name = "quicksort_1"]
+    #[link_name = "quicksort_1_exposed"]
     fn quicksort(list: RocList<i64>) -> RocList<i64>;
 }
 

roc_std/src/lib.rs

@@ -426,3 +426,39 @@ impl Drop for RocStr {
         }
     }
 }
+
+#[allow(non_camel_case_types)]
+type c_char = u8;
+
+#[repr(u64)]
+pub enum RocCallResult<T> {
+    Success(T),
+    Failure(*mut c_char),
+}
+
+impl<T: Sized> Into<Result<T, &'static str>> for RocCallResult<T> {
+    fn into(self) -> Result<T, &'static str> {
+        use RocCallResult::*;
+
+        match self {
+            Success(value) => Ok(value),
+            Failure(failure) => Err({
+                let msg = unsafe {
+                    let mut null_byte_index = 0;
+                    loop {
+                        if *failure.offset(null_byte_index) == 0 {
+                            break;
+                        }
+                        null_byte_index += 1;
+                    }
+
+                    let bytes = core::slice::from_raw_parts(failure, null_byte_index as usize);
+
+                    core::str::from_utf8_unchecked(bytes)
+                };
+
+                msg
+            }),
+        }
+    }
+}