commit 40226ab58adb35ed90ff9c313fefbca8e3c4ae2c
author David Tolnay <dtolnay@gmail.com> Tue Mar 03 00:05:35 2020 -0800
committer David Tolnay <dtolnay@gmail.com> Tue Mar 03 00:05:35 2020 -0800
tree baeb95af6a8e21e8554337bc0ff93aa804bdabeb
parent 6c089108e4a1e7fd0cf3e8c61f2d8bf2cdc9bb2f

Implement passing ownership of string to Rust

macro/src/expand.rs

diff --git a/macro/src/expand.rs b/macro/src/expand.rs
index 1896a13..16dab26 100644
--- a/macro/src/expand.rs
+++ b/macro/src/expand.rs
@@ -233,21 +233,17 @@
     let args = efn.args.iter().map(|arg| expand_extern_arg(arg, types));
     let vars = efn.args.iter().map(|arg| {
         let ident = &arg.ident;
-        let var = if types.needs_indirect_abi(&arg.ty) {
-            quote!(::std::ptr::read(#ident))
-        } else {
-            quote!(#ident)
-        };
         match &arg.ty {
-            Type::Ident(ident) if ident == "String" => quote!(#var.into_string()),
-            Type::RustBox(_) => quote!(::std::boxed::Box::from_raw(#var)),
-            Type::UniquePtr(_) => quote!(::cxx::UniquePtr::from_raw(#var)),
+            Type::Ident(i) if i == "String" => quote!(::std::mem::take((*#ident).as_mut_string())),
+            Type::RustBox(_) => quote!(::std::boxed::Box::from_raw(#ident)),
+            Type::UniquePtr(_) => quote!(::cxx::UniquePtr::from_raw(#ident)),
             Type::Ref(ty) => match &ty.inner {
-                Type::Ident(ident) if ident == "String" => quote!(#var.as_string()),
-                _ => var,
+                Type::Ident(i) if i == "String" => quote!(#ident.as_string()),
+                _ => quote!(#ident),
             },
-            Type::Str(_) => quote!(#var.as_str()),
-            _ => var,
+            Type::Str(_) => quote!(#ident.as_str()),
+            ty if types.needs_indirect_abi(ty) => quote!(::std::ptr::read(#ident)),
+            _ => quote!(#ident),
         }
     });
     let mut outparam = None;

src/rust_string.rs

diff --git a/src/rust_string.rs b/src/rust_string.rs
index 43cd5a6..345d969 100644
--- a/src/rust_string.rs
+++ b/src/rust_string.rs
@@ -24,6 +24,10 @@
     pub fn as_string(&self) -> &String {
         &self.repr
     }
+
+    pub fn as_mut_string(&mut self) -> &mut String {
+        &mut self.repr
+    }
 }
 
 #[export_name = "cxxbridge01$string$new"]

tests/ffi/tests.cc

diff --git a/tests/ffi/tests.cc b/tests/ffi/tests.cc
index 65640df..c94e34d 100644
--- a/tests/ffi/tests.cc
+++ b/tests/ffi/tests.cc
@@ -100,7 +100,7 @@
   r_take_unique_ptr(std::unique_ptr<C>(new C{2020}));
   r_take_ref_c(C{2020});
   r_take_str(rust::Str("2020"));
-  // TODO r_take_rust_string(rust::String("2020"));
+  r_take_rust_string(rust::String("2020"));
   r_take_unique_ptr_string(
       std::unique_ptr<std::string>(new std::string("2020")));