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fix: host_bindgen! returns Result instead of panicking on guest errors #1317

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fix: host_bindgen! returns Result instead of panicking on guest errors #1317

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af22583
fix: return guest errors from host bindgen
jsturtevant Jun 19, 2026
9b51041
Updates based on feedback
jsturtevant Jul 28, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
### Fixed
* Fix symbol resolution in guest core dumps for sandboxes created from snapshots by @ludfjig in https://github.com/hyperlight-dev/hyperlight/pull/1618
* Reject malformed OCI snapshot metadata and non-regular artifact files during load.
* Return guest call failures from `host_bindgen!` functions as `HyperlightError` values.

## [v0.16.0] - 2026-06-26

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16 changes: 15 additions & 1 deletion src/hyperlight_component_util/src/emit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -149,13 +149,18 @@ pub struct Trait {
pub tvs: BTreeMap<Ident, (Option<u32>, TokenStream)>,
/// Raw tokens of the contents of the trait
pub items: TokenStream,
/// Trait items keyed by their WIT names. A resource can be reached
/// more than once, e.g. via both the import-side and the export-side
/// trait of an instance, and its trait is shared.
pub extern_decls: BTreeMap<String, TokenStream>,
}
impl Trait {
pub fn new() -> Self {
Self {
supertraits: BTreeMap::new(),
tvs: BTreeMap::new(),
items: TokenStream::new(),
extern_decls: BTreeMap::new(),
}
}
/// Collect the component tyvar indices that correspond to the
Expand Down Expand Up @@ -217,8 +222,9 @@ impl Trait {
.collect::<Vec<_>>();
let tvs = self.tv_toks();
let items = &self.items;
let extern_decls = self.extern_decls.values();
quote! {
pub trait #n #tvs #trait_colon #(#supertraits)+* { #items }
pub trait #n #tvs #trait_colon #(#supertraits)+* { #items #(#extern_decls)* }
}
}
}
Expand All @@ -230,6 +236,10 @@ impl Trait {
pub struct Mod {
pub submods: BTreeMap<Ident, Mod>,
pub items: TokenStream,
/// Definitions keyed by their WIT names. An instance can be reached
/// more than once, e.g. as both an import and an export of a component,
/// and its helper module is shared.
pub extern_decls: BTreeMap<String, TokenStream>,
pub traits: BTreeMap<Ident, Trait>,
pub impls: BTreeMap<(Vec<Ident>, Ident), TokenStream>,
}
Expand All @@ -238,6 +248,7 @@ impl Mod {
Self {
submods: BTreeMap::new(),
items: TokenStream::new(),
extern_decls: BTreeMap::new(),
traits: BTreeMap::new(),
impls: BTreeMap::new(),
}
Expand Down Expand Up @@ -294,6 +305,9 @@ impl Mod {
for (n, mut t) in self.traits {
tt.extend(t.into_tokens(n));
}
for (_, decl) in self.extern_decls {
tt.extend(decl);
}
tt.extend(self.items);
for ((ns, i), t) in self.impls {
tt.extend(quote! {
Expand Down
15 changes: 7 additions & 8 deletions src/hyperlight_component_util/src/host.rs
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Expand Up @@ -59,19 +59,18 @@ fn emit_export_extern_decl<'a, 'b, 'c>(
fn #n(&mut self, #(#param_decls),*) -> #result_decl {
let mut to_cleanup = Vec::<Box<dyn Drop>>::new();
let marshalled = {
let mut rts = self.rt.lock().unwrap();
let mut rts = self.rt.lock()?;
#[allow(clippy::unused_unit)]
(#(#marshal,)*)
};
let #ret = ::hyperlight_host::sandbox::Callable::call::<::std::vec::Vec::<u8>>(&mut self.sb,
#hln,
marshalled,
);
let ::std::result::Result::Ok(#ret) = #ret else { panic!("bad return from guest {:?}", #ret) };
)?;
#[allow(clippy::unused_unit)]
let mut rts = self.rt.lock().unwrap();
let mut rts = self.rt.lock()?;
#[allow(clippy::unused_unit)]
#unmarshal
Ok(#unmarshal)
}
}
}
Expand Down Expand Up @@ -122,7 +121,7 @@ fn emit_export_instance<'a, 'b, 'c>(s: &'c mut State<'a, 'b>, wn: WitName, it: &

let ns = wn.namespace_path();
let nsi = wn.namespace_idents();
let trait_name = kebab_to_type(wn.name);
let trait_name = kebab_to_exports_name(wn.name);
let r#trait = s.r#trait(&nsi, trait_name.clone());
let tvs = r#trait
.tvs
Expand Down Expand Up @@ -166,7 +165,7 @@ impl SelfInfo {
orig_id,
type_id: vec![format_ident!("I")],
inner_preamble: quote! {
let mut #inner_id = #outer_id.lock().unwrap();
let mut #inner_id = #outer_id.lock()?;
let mut #inner_id = ::std::ops::DerefMut::deref_mut(&mut #inner_id);
},
outer_id,
Expand Down Expand Up @@ -245,7 +244,7 @@ fn emit_import_extern_decl<'a, 'b, 'c>(
let #outer_id = #orig_id.clone();
let captured_rts = rts.clone();
sb.register_host_function(#hln, move |#(#pds),*| {
let mut rts = captured_rts.lock().unwrap();
let mut rts = captured_rts.lock()?;
#inner_preamble
let #ret = #callname(
::std::borrow::BorrowMut::<#(#type_id)::*>::borrow_mut(
Expand Down
2 changes: 1 addition & 1 deletion src/hyperlight_component_util/src/resource.rs
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Expand Up @@ -99,7 +99,7 @@ pub fn emit_tables<'a, 'b, 'c>(
#sphantom
}
impl<I: #bound #sv> #rtsid<I #svs> {
fn new() -> Self {
pub(crate) fn new() -> Self {
#rtsid {
#(#inits,)*
_phantomI: ::core::marker::PhantomData,
Expand Down
62 changes: 44 additions & 18 deletions src/hyperlight_component_util/src/rtypes.rs
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Expand Up @@ -573,9 +573,14 @@ pub fn emit_func_param(s: &mut State, p: &Param) -> TokenStream {
/// Precondition: the result type must only be a named result if there
/// are no names in it (i.e. a unit type)
pub fn emit_func_result(s: &mut State, r: &etypes::Result<'_>) -> TokenStream {
match r {
let result = match r {
Some(vt) => emit_value(s, vt),
None => quote! { () },
};
if !s.is_guest && s.is_export {
quote! { ::hyperlight_host::Result<#result> }
} else {
result
}
}

Expand Down Expand Up @@ -681,6 +686,9 @@ fn emit_extern_decl<'a, 'b, 'c>(
FnName::Associated(r, n) => {
let mut s = s.helper();
s.cur_trait = Some(r.clone());
if s.cur_trait().extern_decls.contains_key(ed.kebab_name) {
return quote! {};
}
let mut needs_vars = BTreeSet::new();
let mut sv = s.with_needs_vars(&mut needs_vars);
let params = ft
Expand All @@ -690,21 +698,24 @@ fn emit_extern_decl<'a, 'b, 'c>(
.collect::<Vec<_>>();
match n {
ResourceItemName::Constructor => {
sv.cur_trait().items.extend(quote! {
fn new(&mut self, #(#params),*) -> Self::T;
});
sv.cur_trait().extern_decls.insert(
ed.kebab_name.to_string(),
quote! { fn new(&mut self, #(#params),*) -> Self::T; },
);
}
ResourceItemName::Method(n) => {
let result = emit_func_result(&mut sv, &ft.result);
sv.cur_trait().items.extend(quote! {
fn #n(&mut self, #(#params),*) -> #result;
});
sv.cur_trait().extern_decls.insert(
ed.kebab_name.to_string(),
quote! { fn #n(&mut self, #(#params),*) -> #result; },
);
}
ResourceItemName::Static(n) => {
let result = emit_func_result(&mut sv, &ft.result);
sv.cur_trait().items.extend(quote! {
fn #n(&mut self, #(#params),*) -> #result;
});
sv.cur_trait().extern_decls.insert(
ed.kebab_name.to_string(),
quote! { fn #n(&mut self, #(#params),*) -> #result; },
);
}
}
for v in needs_vars {
Expand All @@ -724,9 +735,14 @@ fn emit_extern_decl<'a, 'b, 'c>(
) -> TokenStream {
let id = kebab_to_type(ed.kebab_name);
let mut s = s.helper();
if s.cur_mod().extern_decls.contains_key(ed.kebab_name) {
return TokenStream::new();
}

let t = emit_defined(&mut s, v, id, t);
s.cur_mod().items.extend(t);
s.cur_mod()
.extern_decls
.insert(ed.kebab_name.to_string(), t);
TokenStream::new()
}
let edn: &'b str = ed.kebab_name;
Expand All @@ -746,9 +762,12 @@ fn emit_extern_decl<'a, 'b, 'c>(
s.add_helper_supertrait(rn.clone());
let mut s = s.helper();
s.cur_trait = Some(rn.clone());
s.cur_trait().items.extend(quote! {
type T: ::core::marker::Send;
});
if !s.cur_trait().extern_decls.contains_key(ed.kebab_name) {
s.cur_trait().extern_decls.insert(
ed.kebab_name.to_string(),
quote! { type T: ::core::marker::Send; },
);
}
quote! {}
}
}
Expand All @@ -762,7 +781,12 @@ fn emit_extern_decl<'a, 'b, 'c>(
emit_instance(&mut s, wn.clone(), it);

let nsids = wn.namespace_idents();
let repr = s.r#trait(&nsids, kebab_to_type(wn.name));
let trait_tn = if !s.is_guest && s.is_export {
kebab_to_exports_name(wn.name)
} else {
kebab_to_type(wn.name)
};
let repr = s.r#trait(&nsids, trait_tn.clone());
let vs = if !repr.tvs.is_empty() {
let vs = repr.tvs.clone();
let tvs = vs
Expand All @@ -780,7 +804,6 @@ fn emit_extern_decl<'a, 'b, 'c>(
};
let rp = s.root_path();
let tns = wn.namespace_path();
let trait_tn = kebab_to_type(wn.name);
let trait_bound = if tns.is_empty() {
quote! { #rp #trait_tn }
} else {
Expand All @@ -803,7 +826,11 @@ fn emit_instance<'a, 'b, 'c>(s: &'c mut State<'a, 'b>, wn: WitName, it: &'c Inst
tracing::debug!("emitting instance {:?}", wn);
let mut s = s.with_cursor(wn.namespace_idents());

let name = kebab_to_type(wn.name);
let name = if !s.is_guest && s.is_export {
kebab_to_exports_name(wn.name)
} else {
kebab_to_type(wn.name)
};

s.cur_helper_mod = Some(kebab_to_namespace(wn.name));
s.cur_trait = Some(name.clone());
Expand Down Expand Up @@ -857,7 +884,6 @@ fn emit_instance<'a, 'b, 'c>(s: &'c mut State<'a, 'b>, wn: WitName, it: &'c Inst
let id = s.noff_var_id(v);
s.cur_trait().tvs.insert(id, (Some(v), TokenStream::new()));
}

s.cur_trait().items.extend(quote! { #(#exports)* });
}

Expand Down
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