Add well placed unwind(allowed) attribute

lib/runtime-core/Cargo.toml

@@ -45,6 +45,7 @@ field-offset = "0.1.1"
 
 [build-dependencies]
 blake2b_simd = "0.4.1"
+rustc_version = "0.2.3"
 
 [features]
 debug = []

lib/runtime-core/build.rs

@@ -23,4 +23,9 @@ fn main() {
     f_out
         .write_all(hash_string.as_bytes())
         .expect("Could not write to file for wasmer hash value");
+
+    // Enable "nightly" cfg if the current compiler is nightly.
+    if rustc_version::version_meta().unwrap().channel == rustc_version::Channel::Nightly {
+        println!("cargo:rustc-cfg=nightly");
+    }
 }

lib/runtime-core/src/lib.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(nightly, feature(unwind_attributes))]
+
 #[cfg(test)]
 #[macro_use]
 extern crate field_offset;

lib/runtime-core/src/typed_func.rs

@@ -339,11 +339,14 @@ macro_rules! impl_traits {
             fn to_raw(&self) -> NonNull<vm::Func> {
                 assert_eq!(mem::size_of::<Self>(), 0, "you cannot use a closure that captures state for `Func`.");
 
+                /// This is required for the llvm backend to be able to unwind through this function.
+                #[cfg_attr(nightly, unwind(allowed))]
                 extern fn wrap<$( $x: WasmExternType, )* Rets: WasmTypeList, Trap: TrapEarly<Rets>, FN: Fn( &mut Ctx $( ,$x )* ) -> Trap>( ctx: &mut Ctx $( ,$x: $x )* ) -> Rets::CStruct {
                     let f: FN = unsafe { mem::transmute_copy(&()) };
 
                     let err = match panic::catch_unwind(panic::AssertUnwindSafe(|| {
-                        f( ctx $( ,$x )* ).report()
+                        let res = f( ctx $( ,$x )* ).report();
+                        res
                     })) {
                         Ok(Ok(returns)) => return returns.into_c_struct(),
                         Ok(Err(err)) => err,