Use more #[repr(transparent)]

Fixes #46

Author: Boddlnagg

README.md

@@ -8,7 +8,7 @@ This library is still subject to breaking changes, but it is already possible to
 Creating custom WinRT classes using inheritance is not yet supported, so it is currently not possible to create user interfaces using *XAML*. 
 
 ## Prerequisites
-Using this crate requires at least Rust 1.25.
+Using this crate requires at least Rust 1.28.
 Additional nightly features (e.g. using specialization) can be enabled with the `nightly` Cargo feature.
 
 ## Design

src/cominterfaces.rs

@@ -37,7 +37,8 @@ DEFINE_IID!(IID_IAgileObject, 0x94EA2B94, 0xE9CC, 0x49E0, 0xC0, 0xFF, 0xEE, 0x64
 
 /// Interface that marks an object as agile.
 /// It inherits from `IUnknown` and does not have additional members.
-#[repr(C)] #[derive(Debug)]
+#[repr(transparent)]
+#[derive(Debug)]
 pub struct IAgileObject {
     lpVtbl: *const IUnknownVtbl // IAgileObject has no methods besides what IUnknown has
 }

src/hstring.rs

@@ -47,6 +47,7 @@ fn zero_header() -> HSTRING_HEADER {
 
 /// A reference to either an `HString`, a `FastHString`, or a raw null-terminated UTF-16 buffer.
 #[derive(Copy, Clone)]
+#[repr(transparent)]
 pub struct HStringReference<'a>(HSTRING_HEADER, PhantomData<&'a ()>);
 
 impl<'a> HStringReference<'a> {
@@ -164,6 +165,7 @@ impl<'a> Deref for HStringReference<'a> {
 /// functions. Creating a new `FastHString` is faster than creating an instance of `HString`
 /// because it eliminates an additional allocation. Furthermore, obtaining a `HStringArg` from
 /// a `FastHString` is basically free, which is not the case for `HString`.
+#[repr(transparent)]
 pub struct FastHString(HSTRING_HEADER);
 
 impl FastHString {
@@ -341,6 +343,7 @@ impl<'a> Deref for FastHString {
 /// References of this type are passed to WinRT functions. You can not create a value of
 /// this type, only references can exist and are obtained via (automatic) dereferencing of
 /// `FastHString` or `HStringReference`.
+#[repr(transparent)]
 pub struct HStringArg(HSTRING_HEADER);
 
 impl HStringArg {
@@ -358,6 +361,7 @@ impl HStringArg {
 /// the containing `HSTRING` might be null (empty string), and null references
 /// are not allowed. In order to obtain an `&HStringArg` from an `HString`,
 /// first create an `HStringReference` using `make_reference()`.
+#[repr(transparent)]
 pub struct HString(HSTRING);
 
 impl HString {

src/rt/mod.rs

@@ -20,7 +20,8 @@ use self::gen::windows::foundation::collections::{
 };
 
 /// Represents a single UTF-16 character. This is the standard character type in WinRT. 
-#[derive(Clone, Copy)] #[repr(C)]
+#[derive(Clone, Copy)]
+#[repr(transparent)]
 pub struct Char(pub ::w::ctypes::wchar_t); // TODO: deref to u16
 
 /// Marker trait for all Windows Runtime interfaces. They must inherit from `IInspectable`.
@@ -276,11 +277,11 @@ macro_rules! RT_INTERFACE {
     ($(#[$attr:meta])* basic $interface:ident ($vtbl:ident) : $pinterface:ident ($pvtbl:ty) [$iid:ident]
         {}
     ) => {
-        #[repr(C)] #[allow(missing_copy_implementations)] #[doc(hidden)]
+        #[repr(transparent)] #[allow(missing_copy_implementations)] #[doc(hidden)]
         pub struct $vtbl {
             pub parent: $pvtbl
         }
-        $(#[$attr])* #[repr(C)] #[allow(missing_copy_implementations)]
+        $(#[$attr])* #[repr(transparent)] #[allow(missing_copy_implementations)]
         pub struct $interface {
             lpVtbl: *const $vtbl
         }
@@ -329,7 +330,7 @@ macro_rules! RT_INTERFACE {
                 $(,$p: $t)*
             ) -> $rtr)+
         }
-        $(#[$attr])* #[repr(C)] #[allow(missing_copy_implementations)]
+        $(#[$attr])* #[repr(transparent)] #[allow(missing_copy_implementations)]
         pub struct $interface {
             lpVtbl: *const $vtbl
         }
@@ -378,7 +379,7 @@ macro_rules! RT_INTERFACE {
                 $(,$p: $t)*
             ) -> $rtr)+
         }
-        $(#[$attr])* #[repr(C)] #[allow(missing_copy_implementations)]
+        $(#[$attr])* #[repr(transparent)] #[allow(missing_copy_implementations)]
         pub struct $interface<$t1> where $t1: RtType {
             lpVtbl: *const $vtbl<$t1>,
         }
@@ -423,7 +424,7 @@ macro_rules! RT_INTERFACE {
                 $(,$p: $t)*
             ) -> $rtr)+
         }
-        $(#[$attr])* #[repr(C)] #[allow(missing_copy_implementations)]
+        $(#[$attr])* #[repr(transparent)] #[allow(missing_copy_implementations)]
         pub struct $interface<$t1, $t2> where $t1: RtType, $t2: RtType {
             lpVtbl: *const $vtbl<$t1, $t2>,
         }
@@ -649,7 +650,8 @@ macro_rules! DEFINE_CLSID {
 
 macro_rules! RT_ENUM {
     {enum $name:ident : $t:ty { $($variant:ident = $value:expr,)+ }} => {
-        #[repr(C)] #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+        #[repr(transparent)]
+        #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
         #[allow(non_upper_case_globals)]
         pub struct $name(pub $t);