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Fix memory leak for Option<SwiftType> #273

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merged 1 commit into from
Apr 29, 2024
Merged

Fix memory leak for Option<SwiftType> #273

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12 changes: 11 additions & 1 deletion crates/swift-bridge-ir/src/bridged_type/bridged_opaque_type.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -324,8 +324,18 @@ impl BridgeableType for OpaqueForeignType {
HostLang::Swift => {
let ty = &self.ty;

// Here we are converting a Swift type from its Rust representation to its FFI
// representation.
// When we drop the Rust representation we do not want to free the backing Swift
// type since we are passing ownership to Swift.
// So, we are transitioning this Swift type from its
// `RustRepr -> FfiRepr -> SwiftRepr`.
// This means that the Swift side will be responsible for freeing the Swift type
// whenever it is done with it.
// Here we use `ManuallyDrop` to avoid freeing the Swift type.
quote! {
if let Some(val) = #expression {
let val = std::mem::ManuallyDrop::new(val);
val.0 as *mut super::#ty
} else {
std::ptr::null_mut()
Expand Down Expand Up @@ -434,7 +444,7 @@ impl BridgeableType for OpaqueForeignType {
format!("{{ if let val = {expression} {{ val.isOwned = false; return val.ptr }} else {{ return nil }} }}()", expression = expression,)
}
HostLang::Swift => {
format!("{{ if let val = {expression} {{ return Unmanaged.passRetained(val).retain().toOpaque() }} else {{ return nil }} }}()")
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passRetained already increments the retain count. We do not want to increment it twice.

format!("{{ if let val = {expression} {{ return Unmanaged.passRetained(val).toOpaque() }} else {{ return nil }} }}()")
}
}
}
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3 changes: 2 additions & 1 deletion crates/swift-bridge-ir/src/codegen/codegen_tests/option_codegen_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -676,6 +676,7 @@ mod extern_rust_fn_return_option_opaque_swift_type {
#[export_name = "__swift_bridge__$some_function"]
pub extern "C" fn __swift_bridge__some_function() -> *mut super::SomeSwiftType {
if let Some(val) = super::some_function() {
let val = std::mem::ManuallyDrop::new(val);
val.0 as *mut super::SomeSwiftType
} else {
std::ptr::null_mut()
Expand Down Expand Up @@ -945,7 +946,7 @@ mod extern_rust_fn_with_option_opaque_swift_type_arg {
ExpectedSwiftCode::ContainsAfterTrim(
r#"
func some_function(_ arg: Optional<SomeSwiftType>) {
__swift_bridge__$some_function({ if let val = arg { return Unmanaged.passRetained(val).retain().toOpaque() } else { return nil } }())
__swift_bridge__$some_function({ if let val = arg { return Unmanaged.passRetained(val).toOpaque() } else { return nil } }())
}
"#,
)
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