commit 25b3c1d1e212e854c0140818b86de7287f6301e7
author David Tolnay <dtolnay@gmail.com> Sat Dec 12 15:50:10 2020 -0800
committer David Tolnay <dtolnay@gmail.com> Sat Dec 12 16:29:34 2020 -0800
tree 3ccb8fd1f0c9ac70d6c0b10a470c5c4ec060504b
parent 4bd77b65dfda3777ae15771059f18b6ce2c7ad0b

Add dealloc shim for Box to dealloc without running T's Drop

gen/src/write.rs

diff --git a/gen/src/write.rs b/gen/src/write.rs
index fc0872f..cbad93c 100644
--- a/gen/src/write.rs
+++ b/gen/src/write.rs
@@ -1353,6 +1353,11 @@
     );
     writeln!(
         out,
+        "void cxxbridge1$box${}$dealloc({} *) noexcept;",
+        instance, inner,
+    );
+    writeln!(
+        out,
         "void cxxbridge1$box${}$drop(::rust::Box<{}> *ptr) noexcept;",
         instance, inner,
     );
@@ -1420,6 +1425,15 @@
     writeln!(out, "}}");
 
     writeln!(out, "template <>");
+    writeln!(
+        out,
+        "void Box<{}>::dealloc({} *ptr) noexcept {{",
+        inner, inner,
+    );
+    writeln!(out, "  cxxbridge1$box${}$dealloc(ptr);", instance);
+    writeln!(out, "}}");
+
+    writeln!(out, "template <>");
     writeln!(out, "void Box<{}>::drop() noexcept {{", inner);
     writeln!(out, "  cxxbridge1$box${}$drop(this);", instance);
     writeln!(out, "}}");

include/cxx.h

diff --git a/include/cxx.h b/include/cxx.h
index 34b8771..a1e1700 100644
--- a/include/cxx.h
+++ b/include/cxx.h
@@ -229,6 +229,7 @@
   class uninit;
   Box(uninit) noexcept;
   static T *alloc() noexcept;
+  static void dealloc(T *) noexcept;
   void drop() noexcept;
   T *ptr;
 };

macro/src/expand.rs

diff --git a/macro/src/expand.rs b/macro/src/expand.rs
index 4a17161..433eca6 100644
--- a/macro/src/expand.rs
+++ b/macro/src/expand.rs
@@ -952,10 +952,12 @@
 fn expand_rust_box(ident: &RustName, types: &Types) -> TokenStream {
     let link_prefix = format!("cxxbridge1$box${}$", types.resolve(ident).to_symbol());
     let link_alloc = format!("{}alloc", link_prefix);
+    let link_dealloc = format!("{}dealloc", link_prefix);
     let link_drop = format!("{}drop", link_prefix);
 
     let local_prefix = format_ident!("{}__box_", &ident.rust);
     let local_alloc = format_ident!("{}alloc", local_prefix);
+    let local_dealloc = format_ident!("{}dealloc", local_prefix);
     let local_drop = format_ident!("{}drop", local_prefix);
 
     let span = ident.span();
@@ -968,6 +970,11 @@
             ::std::boxed::Box::into_raw(::std::boxed::Box::new(::std::mem::MaybeUninit::uninit()))
         }
         #[doc(hidden)]
+        #[export_name = #link_dealloc]
+        unsafe extern "C" fn #local_dealloc(ptr: *mut ::std::mem::MaybeUninit<#ident>) {
+            ::std::boxed::Box::from_raw(ptr);
+        }
+        #[doc(hidden)]
         #[export_name = #link_drop]
         unsafe extern "C" fn #local_drop(this: *mut ::std::boxed::Box<#ident>) {
             ::std::ptr::drop_in_place(this);