diff options
| -rw-r--r-- | src/liballoc/boxed.rs | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs index 01dee0a3943..50174c3f279 100644 --- a/src/liballoc/boxed.rs +++ b/src/liballoc/boxed.rs @@ -63,6 +63,28 @@ //! T` obtained from `Box::<T>::into_raw` may be deallocated using the //! [`Global`] allocator with `Layout::for_value(&*value)`. //! +//! `Box<T>` has the same representation as `*mut T`. In particular, when +//! `T: Sized`, this means that `Box<T>` has the same representation as +//! a C pointer, making the following code valid in FFI: +//! +//! ```c +//! /* C header */ +//! struct Foo* foo(); /* Returns ownership */ +//! void bar(struct Foo*); /* `bar` takes ownership */ +//! ``` +//! +//! ``` +//! #[repr(C)] +//! pub struct Foo; +//! +//! #[no_mangle] +//! pub extern "C" fn foo() -> Box<Foo> { +//! Box::new(Foo) +//! } +//! +//! #[no_mangle] +//! pub extern "C" fn bar(_: Option<Box<Foo>>) {} +//! ``` //! //! [dereferencing]: ../../std/ops/trait.Deref.html //! [`Box`]: struct.Box.html |