Allow returning traps from linked closures

Author: jonas-schievink

examples/wasm_link_closure.rs

@@ -16,11 +16,11 @@ fn main() {
 
     let mut module = rt.load_module(module).expect("Unable to load module");
     module
-        .link_closure("time", "millis", |_, ()| MILLIS)
+        .link_closure("time", "millis", |_, ()| Ok(MILLIS))
         .expect("Unable to link closure");
     let func = module
         .find_function::<(), u64>("seconds")
         .expect("Unable to find function");
-    println!("{}ms in seconds is {:?}s.", MILLIS, func.call());
+    println!("{}ms in seconds is {:?}s.", MILLIS, func.call().unwrap());
     assert_eq!(func.call(), Ok(MILLIS / 1000));
 }

examples/wasm_link_closure_trap.rs

@@ -0,0 +1,34 @@
+use wasm3::error::Error;
+use wasm3::error::Trap;
+use wasm3::Environment;
+use wasm3::Module;
+
+fn main() {
+    let env = Environment::new().expect("Unable to create environment");
+    let rt = env
+        .create_runtime(1024 * 60)
+        .expect("Unable to create runtime");
+    let module = Module::parse(
+        &env,
+        &include_bytes!("wasm/wasm_millis_to_seconds/wasm_millis_to_seconds.wasm")[..],
+    )
+    .expect("Unable to parse module");
+
+    let mut module = rt.load_module(module).expect("Unable to load module");
+    module
+        .link_closure("time", "millis", |_, ()| Err::<u64, _>(Trap::Abort))
+        .expect("Unable to link closure");
+    let func = module
+        .find_function::<(), u64>("seconds")
+        .expect("Unable to find function");
+
+    let err = func.call().unwrap_err();
+    match err {
+        Error::Wasm3(e) if e.is_trap(Trap::Abort) => {
+            println!("got expected error: {}", e);
+        }
+        _ => {
+            panic!("unexpected error: {}", err)
+        }
+    }
+}

src/module.rs

@@ -5,7 +5,7 @@ use core::ptr::{self, NonNull};
 use core::slice;
 
 use crate::environment::Environment;
-use crate::error::{Error, Result};
+use crate::error::{Error, Result, Trap};
 use crate::function::{CallContext, Function, NNM3Function, RawCall};
 use crate::runtime::Runtime;
 use crate::utils::{cstr_to_str, eq_cstr_str};
@@ -123,7 +123,7 @@ impl<'rt> Module<'rt> {
     where
         Args: crate::WasmArgs,
         Ret: crate::WasmType,
-        F: for<'cc> FnMut(CallContext<'cc>, Args) -> Ret + 'static,
+        F: for<'cc> FnMut(CallContext<'cc>, Args) -> core::result::Result<Ret, Trap> + 'static,
     {
         let func = self.find_import_function(module_name, function_name)?;
         Function::<'_, Args, Ret>::validate_sig(func)?;
@@ -234,7 +234,7 @@ impl<'rt> Module<'rt> {
     where
         Args: crate::WasmArgs,
         Ret: crate::WasmType,
-        F: for<'cc> FnMut(CallContext<'cc>, Args) -> Ret + 'static,
+        F: for<'cc> FnMut(CallContext<'cc>, Args) -> core::result::Result<Ret, Trap> + 'static,
     {
         unsafe extern "C" fn _impl<Args, Ret, F>(
             runtime: ffi::IM3Runtime,
@@ -245,7 +245,7 @@ impl<'rt> Module<'rt> {
         where
             Args: crate::WasmArgs,
             Ret: crate::WasmType,
-            F: for<'cc> FnMut(CallContext<'cc>, Args) -> Ret + 'static,
+            F: for<'cc> FnMut(CallContext<'cc>, Args) -> core::result::Result<Ret, Trap> + 'static,
         {
             // use https://doc.rust-lang.org/std/primitive.pointer.html#method.offset_from once stable
             let stack_base = (*runtime).stack as ffi::m3stack_t;
@@ -258,9 +258,14 @@ impl<'rt> Module<'rt> {
 
             let args = Args::pop_from_stack(stack);
             let context = CallContext::from_rt(NonNull::new_unchecked(runtime));
-            let ret = (&mut *closure.cast::<F>())(context, args);
-            ret.push_on_stack(stack.cast());
-            ffi::m3Err_none as _
+            let res = (&mut *closure.cast::<F>())(context, args);
+            match res {
+                Ok(ret) => {
+                    ret.push_on_stack(stack.cast());
+                    ffi::m3Err_none as _
+                }
+                Err(err) => err.as_ptr() as _,
+            }
         }
 
         let page = wasm3_priv::AcquireCodePageWithCapacity(self.rt.as_ptr(), 3);