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Merged
merged 4 commits into from
Nov 19, 2025
Merged

variant case #1424

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7bb70a4
fix(cpp): support worlds with types
ricochet Nov 19, 2025
acd61c6
feat(cpp): handle multiple return areas
ricochet Nov 19, 2025
33ad8c0
fix(cpp): mirror namespacing fix for imports
ricochet Nov 19, 2025
3f784d1
fix(cpp): shared ret_area instance
ricochet Nov 19, 2025
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139 changes: 101 additions & 38 deletions crates/cpp/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -591,13 +591,14 @@ impl WorldGenerator for Cpp {

fn import_types(
&mut self,
_resolve: &Resolve,
resolve: &Resolve,
_world: WorldId,
types: &[(&str, TypeId)],
_files: &mut Files,
) {
for i in types.iter() {
uwriteln!(self.h_src.src, "// import_type {}", i.0);
let mut gen = self.interface(resolve, None, true, Some("$root".to_string()));
for (name, id) in types.iter() {
gen.define_type(name, *id);
}
}

Expand Down Expand Up @@ -973,6 +974,8 @@ impl CppInterfaceGenerator<'_> {
Some(ref module_name) => make_external_symbol(module_name, &func_name, symbol_variant),
None => make_external_component(&func_name),
};
// Add prefix to C ABI export functions to avoid conflicts with C++ namespaces
self.gen.c_src.src.push_str("__wasm_export_");
if let Some(prefix) = self.gen.opts.export_prefix.as_ref() {
self.gen.c_src.src.push_str(prefix);
}
Expand Down Expand Up @@ -1335,7 +1338,8 @@ impl CppInterfaceGenerator<'_> {
f.needs_dealloc = needs_dealloc;
f.cabi_post = None;
abi::call(f.gen.resolve, variant, lift_lower, func, &mut f, false);
let code = String::from(f.src);
let ret_area_decl = f.emit_ret_area_if_needed();
let code = format!("{}{}", ret_area_decl, String::from(f.src));
self.gen.c_src.src.push_str(&code);
}
}
Expand Down Expand Up @@ -1379,8 +1383,9 @@ impl CppInterfaceGenerator<'_> {
let mut f = FunctionBindgen::new(self, params.clone());
f.params = params;
abi::post_return(f.gen.resolve, func, &mut f);
let FunctionBindgen { src, .. } = f;
self.gen.c_src.src.push_str(&src);
let ret_area_decl = f.emit_ret_area_if_needed();
let code = format!("{}{}", ret_area_decl, String::from(f.src));
self.gen.c_src.src.push_str(&code);
self.gen.c_src.src.push_str("}\n");
}
}
Expand Down Expand Up @@ -1636,7 +1641,8 @@ impl CppInterfaceGenerator<'_> {
result: &str,
variant: AbiVariant,
) -> (String, String) {
let extern_name = make_external_symbol(module_name, name, variant);
let mut extern_name = String::from("__wasm_import_");
extern_name.push_str(&make_external_symbol(module_name, name, variant));
let import = format!("extern \"C\" __attribute__((import_module(\"{module_name}\")))\n __attribute__((import_name(\"{name}\")))\n {result} {extern_name}({args});\n")
;
(extern_name, import)
Expand Down Expand Up @@ -2103,6 +2109,8 @@ struct FunctionBindgen<'a, 'b> {
cabi_post: Option<CabiPostInformation>,
needs_dealloc: bool,
leak_on_insertion: Option<String>,
return_pointer_area_size: ArchitectureSize,
return_pointer_area_align: Alignment,
}

impl<'a, 'b> FunctionBindgen<'a, 'b> {
Expand All @@ -2120,6 +2128,8 @@ impl<'a, 'b> FunctionBindgen<'a, 'b> {
cabi_post: None,
needs_dealloc: false,
leak_on_insertion: None,
return_pointer_area_size: Default::default(),
return_pointer_area_align: Default::default(),
}
}

Expand Down Expand Up @@ -2191,6 +2201,47 @@ impl<'a, 'b> FunctionBindgen<'a, 'b> {
operands[0]
);
}

/// Emits a shared return area declaration if needed by this function.
///
/// During code generation, `return_pointer()` may be called multiple times for:
/// - Indirect parameter storage (when too many/large params)
/// - Return value storage (when return type is too large)
///
/// **Safety:** This is safe because return pointers are used sequentially:
/// 1. Parameter marshaling (before call)
/// 2. Function execution
/// 3. Return value unmarshaling (after call)
///
/// The scratch space is reused but never accessed simultaneously.
fn emit_ret_area_if_needed(&self) -> String {
if !self.return_pointer_area_size.is_empty() {
let size_string = self
.return_pointer_area_size
.format(POINTER_SIZE_EXPRESSION);
let tp = match self.return_pointer_area_align {
Alignment::Bytes(bytes) => match bytes.get() {
1 => "uint8_t",
2 => "uint16_t",
4 => "uint32_t",
8 => "uint64_t",
// Fallback to uint8_t for unusual alignments (e.g., 16-byte SIMD).
// This is safe: the size calculation ensures correct buffer size,
// and uint8_t arrays can store any data regardless of alignment.
_ => "uint8_t",
},
Alignment::Pointer => "uintptr_t",
};
let static_var = if self.gen.in_guest_import {
""
} else {
"static "
};
format!("{static_var}{tp} ret_area[({size_string}+sizeof({tp})-1)/sizeof({tp})];\n")
} else {
String::new()
}
}
}

fn move_if_necessary(arg: &str) -> String {
Expand Down Expand Up @@ -2502,14 +2553,25 @@ impl<'a, 'b> Bindgen for FunctionBindgen<'a, 'b> {
results.push(result);
}
abi::Instruction::HandleLower {
handle: Handle::Own(_ty),
handle: Handle::Own(ty),
..
} => {
let op = &operands[0];
if matches!(self.variant, AbiVariant::GuestImport) {
results.push(format!("{op}.into_handle()"));
} else {

// Check if this is an imported or exported resource
let resource_ty = &self.gen.resolve.types[*ty];
let resource_ty = match &resource_ty.kind {
TypeDefKind::Type(Type::Id(id)) => &self.gen.resolve.types[*id],
_ => resource_ty,
};
let is_exported = self.gen.is_exported_type(resource_ty);

if is_exported {
// Exported resources use .release()->handle
results.push(format!("{op}.release()->handle"));
} else {
// Imported resources use .into_handle()
results.push(format!("{op}.into_handle()"));
}
}
abi::Instruction::HandleLower {
Expand Down Expand Up @@ -2633,7 +2695,13 @@ impl<'a, 'b> Bindgen for FunctionBindgen<'a, 'b> {
.join(", "),
);
self.src.push_str(">(");
self.src.push_str(&operands.join(", "));
self.src.push_str(
&operands
.iter()
.map(|op| move_if_necessary(op))
.collect::<Vec<_>>()
.join(", "),
);
self.src.push_str(");\n");
results.push(format!("std::move({name})"));
}
Expand Down Expand Up @@ -2715,14 +2783,12 @@ impl<'a, 'b> Bindgen for FunctionBindgen<'a, 'b> {
variant.cases.iter().zip(blocks).zip(payloads).enumerate()
{
uwriteln!(self.src, "case {}: {{", i);
if let Some(ty) = case.ty.as_ref() {
let ty = self.gen.type_name(ty, &self.namespace, Flavor::InStruct);
if case.ty.is_some() {
let case =
format!("{elem_ns}::{}", to_c_ident(&case.name).to_pascal_case());
uwriteln!(
self.src,
"{} &{} = std::get<{case}>({}.variants).value;",
ty,
"auto& {} = std::get<{case}>({}.variants).value;",
payload,
operands[0],
);
Expand Down Expand Up @@ -2998,7 +3064,13 @@ impl<'a, 'b> Bindgen for FunctionBindgen<'a, 'b> {
}
self.src.push_str(&func);
self.src.push_str("(");
self.src.push_str(&operands.join(", "));
self.src.push_str(
&operands
.iter()
.map(|op| move_if_necessary(op))
.collect::<Vec<_>>()
.join(", "),
);
self.src.push_str(");\n");
}
abi::Instruction::CallInterface { func, .. } => {
Expand All @@ -3015,7 +3087,13 @@ impl<'a, 'b> Bindgen for FunctionBindgen<'a, 'b> {
}
self.src.push_str(&func_name_h);
self.push_str("(");
self.push_str(&operands.join(", "));
self.push_str(
&operands
.iter()
.map(|op| move_if_necessary(op))
.collect::<Vec<_>>()
.join(", "),
);
self.push_str(");\n");
if self.needs_dealloc {
uwriteln!(
Expand Down Expand Up @@ -3171,27 +3249,12 @@ impl<'a, 'b> Bindgen for FunctionBindgen<'a, 'b> {
}

fn return_pointer(&mut self, size: ArchitectureSize, align: Alignment) -> Self::Operand {
// Track maximum return area requirements
self.return_pointer_area_size = self.return_pointer_area_size.max(size);
self.return_pointer_area_align = self.return_pointer_area_align.max(align);

// Generate pointer to shared ret_area
let tmp = self.tmp();
let size_string = size.format(POINTER_SIZE_EXPRESSION);
let tp = match align {
Alignment::Bytes(bytes) => match bytes.get() {
1 => "uint8_t",
2 => "uint16_t",
4 => "uint32_t",
8 => "uint64_t",
_ => todo!(),
},
Alignment::Pointer => "uintptr_t",
};
let static_var = if self.gen.in_guest_import {
""
} else {
"static "
};
uwriteln!(
self.src,
"{static_var}{tp} ret_area[({size_string}+sizeof({tp})-1)/sizeof({tp})];"
);
uwriteln!(
self.src,
"{} ptr{tmp} = ({0})(&ret_area);",
Expand Down
11 changes: 0 additions & 11 deletions crates/test/src/cpp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,11 +49,6 @@ impl LanguageMethods for Cpp {
"async-trait-function.wit"
| "error-context.wit"
| "futures.wit"
| "import_export_func.wit"
| "import-func.wit"
| "issue573.wit"
| "issue929-no-export.wit"
| "lift-lower-foreign.wit"
| "lists.wit"
| "multiversion"
| "resource-alias.wit"
Expand All @@ -63,13 +58,7 @@ impl LanguageMethods for Cpp {
| "resources-in-aggregates.wit"
| "resources-with-futures.wit"
| "resources-with-streams.wit"
| "ret-areas.wit"
| "return-resource-from-export.wit"
| "same-names1.wit"
| "same-names5.wit"
| "variants.wit"
| "variants-unioning-types.wit"
| "worlds-with-types.wit"
| "streams.wit" => true,
_ => false,
}
Expand Down
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