Merge pull request #94 from dtolnay/uniquenew

Do not emit UniquePtr::new for opaque C types
dtolnay · Apr 10, 2020 · eb0ac1a · eb0ac1a
2 parents b1637ad + 5383891
commit eb0ac1a
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Showing 3 changed files with 43 additions and 25 deletions.
diff --git a/gen/write.rs b/gen/write.rs
@@ -766,7 +766,7 @@ fn write_generic_instantiations(out: &mut OutFile, types: &Types) {
             if let Type::Ident(inner) = &ptr.inner {
                 if allow_unique_ptr(inner) {
                     out.next_section();
-                    write_unique_ptr(out, inner);
+                    write_unique_ptr(out, inner, types);
                 }
             }
         }
@@ -830,7 +830,7 @@ fn write_rust_box_impl(out: &mut OutFile, ident: &Ident) {
     writeln!(out, "}}");
 }
 
-fn write_unique_ptr(out: &mut OutFile, ident: &Ident) {
+fn write_unique_ptr(out: &mut OutFile, ident: &Ident, types: &Types) {
     out.include.utility = true;
 
     let mut inner = String::new();
@@ -860,17 +860,19 @@ fn write_unique_ptr(out: &mut OutFile, ident: &Ident) {
     );
     writeln!(out, "  new (ptr) ::std::unique_ptr<{}>();", inner);
     writeln!(out, "}}");
-    writeln!(
-        out,
-        "void cxxbridge02$unique_ptr${}$new(::std::unique_ptr<{}> *ptr, {} *value) noexcept {{",
-        instance, inner, inner,
-    );
-    writeln!(
-        out,
-        "  new (ptr) ::std::unique_ptr<{}>(new {}(::std::move(*value)));",
-        inner, inner,
-    );
-    writeln!(out, "}}");
+    if types.structs.contains_key(ident) {
+        writeln!(
+            out,
+            "void cxxbridge02$unique_ptr${}$new(::std::unique_ptr<{}> *ptr, {} *value) noexcept {{",
+            instance, inner, inner,
+        );
+        writeln!(
+            out,
+            "  new (ptr) ::std::unique_ptr<{}>(new {}(::std::move(*value)));",
+            inner, inner,
+        );
+        writeln!(out, "}}");
+    }
     writeln!(
         out,
         "void cxxbridge02$unique_ptr${}$raw(::std::unique_ptr<{}> *ptr, {} *raw) noexcept {{",

diff --git a/macro/src/expand.rs b/macro/src/expand.rs
@@ -57,7 +57,7 @@ pub fn bridge(namespace: &Namespace, ffi: ItemMod) -> Result<TokenStream> {
         } else if let Type::UniquePtr(ptr) = ty {
             if let Type::Ident(ident) = &ptr.inner {
                 if Atom::from(ident).is_none() {
-                    expanded.extend(expand_unique_ptr(namespace, ident));
+                    expanded.extend(expand_unique_ptr(namespace, ident, types));
                 }
             }
         }
@@ -474,7 +474,7 @@ fn expand_rust_box(namespace: &Namespace, ident: &Ident) -> TokenStream {
     }
 }
 
-fn expand_unique_ptr(namespace: &Namespace, ident: &Ident) -> TokenStream {
+fn expand_unique_ptr(namespace: &Namespace, ident: &Ident, types: &Types) -> TokenStream {
     let prefix = format!("cxxbridge02$unique_ptr${}{}$", namespace, ident);
     let link_null = format!("{}null", prefix);
     let link_new = format!("{}new", prefix);
@@ -483,6 +483,22 @@ fn expand_unique_ptr(namespace: &Namespace, ident: &Ident) -> TokenStream {
     let link_release = format!("{}release", prefix);
     let link_drop = format!("{}drop", prefix);
 
+    let new_method = if types.structs.contains_key(ident) {
+        Some(quote! {
+            fn __new(mut value: Self) -> *mut ::std::ffi::c_void {
+                extern "C" {
+                    #[link_name = #link_new]
+                    fn __new(this: *mut *mut ::std::ffi::c_void, value: *mut #ident);
+                }
+                let mut repr = ::std::ptr::null_mut::<::std::ffi::c_void>();
+                unsafe { __new(&mut repr, &mut value) }
+                repr
+            }
+        })
+    } else {
+        None
+    };
+
     quote! {
         unsafe impl ::cxx::private::UniquePtrTarget for #ident {
             fn __null() -> *mut ::std::ffi::c_void {
@@ -494,15 +510,7 @@ fn expand_unique_ptr(namespace: &Namespace, ident: &Ident) -> TokenStream {
                 unsafe { __null(&mut repr) }
                 repr
             }
-            fn __new(mut value: Self) -> *mut ::std::ffi::c_void {
-                extern "C" {
-                    #[link_name = #link_new]
-                    fn __new(this: *mut *mut ::std::ffi::c_void, value: *mut #ident);
-                }
-                let mut repr = ::std::ptr::null_mut::<::std::ffi::c_void>();
-                unsafe { __new(&mut repr, &mut value) }
-                repr
-            }
+            #new_method
             unsafe fn __raw(raw: *mut Self) -> *mut ::std::ffi::c_void {
                 extern "C" {
                     #[link_name = #link_raw]

diff --git a/src/unique_ptr.rs b/src/unique_ptr.rs
@@ -118,7 +118,15 @@ pub unsafe trait UniquePtrTarget {
     #[doc(hidden)]
     fn __null() -> *mut c_void;
     #[doc(hidden)]
-    fn __new(value: Self) -> *mut c_void;
+    fn __new(value: Self) -> *mut c_void
+    where
+        Self: Sized,
+    {
+        // Opaque C types do not get this method because they can never exist by
+        // value on the Rust side of the bridge.
+        let _ = value;
+        unreachable!()
+    }
     #[doc(hidden)]
     unsafe fn __raw(raw: *mut Self) -> *mut c_void;
     #[doc(hidden)]