Fixes alignment errors with new Rust union type

This fix creates a new private field with the required aligned size. This new
private field ensures that the union has the required size.

Author: bkchr

src/codegen/mod.rs

@@ -1612,14 +1612,20 @@ impl CodeGenerator for CompInfo {
             );
         }
 
-        if is_union && !self.can_be_rust_union(ctx) {
+        if is_union {
             let layout = layout.expect("Unable to get layout information?");
             let ty = BlobTyBuilder::new(layout).build();
-            let field = StructFieldBuilder::named("bindgen_union_field")
-                .pub_()
-                .build_ty(ty);
+            
+            let field = if self.can_be_rust_union(ctx) {
+                StructFieldBuilder::named("_bindgen_union_align")
+                    .build_ty(ty)
+            } else {
+                struct_layout.saw_union(layout);
 
-            struct_layout.saw_union(layout);
+                StructFieldBuilder::named("bindgen_union_field")
+                    .pub_()
+                    .build_ty(ty)
+            };
 
             fields.push(field);
         }

tests/expectations/tests/16-byte-alignment.rs

@@ -16,6 +16,7 @@ pub struct rte_ipv4_tuple {
 pub union rte_ipv4_tuple__bindgen_ty_1 {
     pub __bindgen_anon_1: rte_ipv4_tuple__bindgen_ty_1__bindgen_ty_1,
     pub sctp_tag: u32,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]
@@ -108,6 +109,7 @@ pub struct rte_ipv6_tuple {
 pub union rte_ipv6_tuple__bindgen_ty_1 {
     pub __bindgen_anon_1: rte_ipv6_tuple__bindgen_ty_1__bindgen_ty_1,
     pub sctp_tag: u32,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]
@@ -188,3 +190,31 @@ impl Clone for rte_ipv6_tuple {
 impl Default for rte_ipv6_tuple {
     fn default() -> Self { unsafe { ::std::mem::zeroed() } }
 }
+#[repr(C)]
+#[derive(Copy)]
+pub union rte_thash_tuple {
+    pub v4: rte_ipv4_tuple,
+    pub v6: rte_ipv6_tuple,
+    _bindgen_union_align: [u8; 48usize],
+}
+#[test]
+fn bindgen_test_layout_rte_thash_tuple() {
+    assert_eq!(::std::mem::size_of::<rte_thash_tuple>() , 48usize , concat ! (
+               "Size of: " , stringify ! ( rte_thash_tuple ) ));
+    assert_eq! (unsafe {
+                & ( * ( 0 as * const rte_thash_tuple ) ) . v4 as * const _ as
+                usize } , 0usize , concat ! (
+                "Alignment of field: " , stringify ! ( rte_thash_tuple ) ,
+                "::" , stringify ! ( v4 ) ));
+    assert_eq! (unsafe {
+                & ( * ( 0 as * const rte_thash_tuple ) ) . v6 as * const _ as
+                usize } , 0usize , concat ! (
+                "Alignment of field: " , stringify ! ( rte_thash_tuple ) ,
+                "::" , stringify ! ( v6 ) ));
+}
+impl Clone for rte_thash_tuple {
+    fn clone(&self) -> Self { *self }
+}
+impl Default for rte_thash_tuple {
+    fn default() -> Self { unsafe { ::std::mem::zeroed() } }
+}

tests/expectations/tests/anon_struct_in_union.rs

@@ -13,6 +13,7 @@ pub struct s {
 #[derive(Copy)]
 pub union s__bindgen_ty_1 {
     pub field: s__bindgen_ty_1_inner,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]

tests/expectations/tests/anon_union.rs

@@ -30,6 +30,7 @@ pub struct TErrorResult_DOMExceptionInfo {
 pub union TErrorResult__bindgen_ty_1 {
     pub mMessage: *mut TErrorResult_Message,
     pub mDOMExceptionInfo: *mut TErrorResult_DOMExceptionInfo,
+    _bindgen_union_align: u64,
 }
 impl Default for TErrorResult__bindgen_ty_1 {
     fn default() -> Self { unsafe { ::std::mem::zeroed() } }

tests/expectations/tests/class.rs

@@ -180,6 +180,7 @@ impl Default for IncompleteArrayNonCopiable {
 pub union Union {
     pub d: f32,
     pub i: ::std::os::raw::c_int,
+    _bindgen_union_align: u32,
 }
 #[test]
 fn bindgen_test_layout_Union() {

tests/expectations/tests/class_with_inner_struct.rs

@@ -41,6 +41,7 @@ impl Clone for A_Segment {
 #[derive(Copy)]
 pub union A__bindgen_ty_1 {
     pub f: ::std::os::raw::c_int,
+    _bindgen_union_align: u32,
 }
 #[test]
 fn bindgen_test_layout_A__bindgen_ty_1() {
@@ -64,6 +65,7 @@ impl Default for A__bindgen_ty_1 {
 #[derive(Copy)]
 pub union A__bindgen_ty_2 {
     pub d: ::std::os::raw::c_int,
+    _bindgen_union_align: u32,
 }
 #[test]
 fn bindgen_test_layout_A__bindgen_ty_2() {
@@ -169,6 +171,7 @@ pub struct C {
 pub union C__bindgen_ty_1 {
     pub mFunc: C__bindgen_ty_1__bindgen_ty_1,
     pub __bindgen_anon_1: C__bindgen_ty_1__bindgen_ty_2,
+    _bindgen_union_align: [u32; 4usize],
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy)]

tests/expectations/tests/issue-493.rs

@@ -63,6 +63,7 @@ pub struct basic_string___short {
 pub union basic_string___short__bindgen_ty_1 {
     pub __size_: ::std::os::raw::c_uchar,
     pub __lx: basic_string_value_type,
+    _bindgen_union_align: u8,
 }
 impl Default for basic_string___short__bindgen_ty_1 {
     fn default() -> Self { unsafe { ::std::mem::zeroed() } }

tests/expectations/tests/jsval_layout_opaque.rs

@@ -81,6 +81,7 @@ pub union jsval_layout {
     pub asPtr: *mut ::std::os::raw::c_void,
     pub asWord: usize,
     pub asUIntPtr: usize,
+    _bindgen_union_align: u64,
 }
 #[repr(C)]
 #[derive(Debug, Copy, Hash)]
@@ -199,6 +200,7 @@ pub union jsval_layout__bindgen_ty_2__bindgen_ty_1 {
     pub i32: i32,
     pub u32: u32,
     pub why: JSWhyMagic,
+    _bindgen_union_align: u32,
 }
 #[test]
 fn bindgen_test_layout_jsval_layout__bindgen_ty_2__bindgen_ty_1() {

tests/expectations/tests/layout_eth_conf.rs

@@ -1529,6 +1529,7 @@ pub union rte_eth_conf__bindgen_ty_2 {
     pub vmdq_dcb_tx_conf: rte_eth_vmdq_dcb_tx_conf,
     pub dcb_tx_conf: rte_eth_dcb_tx_conf,
     pub vmdq_tx_conf: rte_eth_vmdq_tx_conf,
+    _bindgen_union_align: [u32; 3usize],
 }
 #[test]
 fn bindgen_test_layout_rte_eth_conf__bindgen_ty_2() {

tests/expectations/tests/layout_mbuf.rs

@@ -92,6 +92,7 @@ pub union rte_mbuf__bindgen_ty_1 {
     pub refcnt_atomic: rte_atomic16_t,
     /// < Non-atomically accessed refcnt
     pub refcnt: u16,
+    _bindgen_union_align: u16,
 }
 #[test]
 fn bindgen_test_layout_rte_mbuf__bindgen_ty_1() {
@@ -124,6 +125,7 @@ pub union rte_mbuf__bindgen_ty_2 {
     /// < L2/L3/L4 and tunnel information.
     pub packet_type: u32,
     pub __bindgen_anon_1: rte_mbuf__bindgen_ty_2__bindgen_ty_1,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]
@@ -462,6 +464,7 @@ pub union rte_mbuf__bindgen_ty_3 {
     pub sched: rte_mbuf__bindgen_ty_3__bindgen_ty_2,
     /// < User defined tags. See rte_distributor_process()
     pub usr: u32,
+    _bindgen_union_align: [u32; 2usize],
 }
 #[repr(C)]
 #[derive(Copy)]
@@ -474,6 +477,7 @@ pub struct rte_mbuf__bindgen_ty_3__bindgen_ty_1 {
 pub union rte_mbuf__bindgen_ty_3__bindgen_ty_1__bindgen_ty_1 {
     pub __bindgen_anon_1: rte_mbuf__bindgen_ty_3__bindgen_ty_1__bindgen_ty_1__bindgen_ty_1,
     pub lo: u32,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]
@@ -639,6 +643,7 @@ pub union rte_mbuf__bindgen_ty_4 {
     pub userdata: *mut ::std::os::raw::c_void,
     /// < Allow 8-byte userdata on 32-bit
     pub udata64: u64,
+    _bindgen_union_align: u64,
 }
 #[test]
 fn bindgen_test_layout_rte_mbuf__bindgen_ty_4() {
@@ -671,6 +676,7 @@ pub union rte_mbuf__bindgen_ty_5 {
     /// < combined for easy fetch
     pub tx_offload: u64,
     pub __bindgen_anon_1: rte_mbuf__bindgen_ty_5__bindgen_ty_1,
+    _bindgen_union_align: u64,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]

tests/expectations/tests/struct_with_anon_union.rs

@@ -14,6 +14,7 @@ pub struct foo {
 pub union foo__bindgen_ty_1 {
     pub a: ::std::os::raw::c_uint,
     pub b: ::std::os::raw::c_ushort,
+    _bindgen_union_align: u32,
 }
 #[test]
 fn bindgen_test_layout_foo__bindgen_ty_1() {

tests/expectations/tests/struct_with_anon_unnamed_union.rs

@@ -14,6 +14,7 @@ pub struct foo {
 pub union foo__bindgen_ty_1 {
     pub a: ::std::os::raw::c_uint,
     pub b: ::std::os::raw::c_ushort,
+    _bindgen_union_align: u32,
 }
 #[test]
 fn bindgen_test_layout_foo__bindgen_ty_1() {

tests/expectations/tests/struct_with_nesting.rs

@@ -16,6 +16,7 @@ pub union foo__bindgen_ty_1 {
     pub b: ::std::os::raw::c_uint,
     pub __bindgen_anon_1: foo__bindgen_ty_1__bindgen_ty_1,
     pub __bindgen_anon_2: foo__bindgen_ty_1__bindgen_ty_2,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]

tests/expectations/tests/typeref.rs

@@ -68,6 +68,7 @@ pub struct mozilla_StyleShapeSource {
 pub union mozilla_StyleShapeSource__bindgen_ty_1 {
     pub mPosition: *mut mozilla_Position,
     pub mFragmentOrURL: *mut mozilla_FragmentOrURL,
+    _bindgen_union_align: u64,
 }
 impl Default for mozilla_StyleShapeSource__bindgen_ty_1 {
     fn default() -> Self { unsafe { ::std::mem::zeroed() } }

tests/expectations/tests/union-in-ns.rs

@@ -12,6 +12,7 @@ pub mod root {
     #[derive(Copy)]
     pub union bar {
         pub baz: ::std::os::raw::c_int,
+        _bindgen_union_align: u32,
     }
     #[test]
     fn bindgen_test_layout_bar() {

tests/expectations/tests/union_dtor.rs

@@ -8,6 +8,7 @@
 pub union UnionWithDtor {
     pub mFoo: ::std::os::raw::c_int,
     pub mBar: *mut ::std::os::raw::c_void,
+    _bindgen_union_align: u64,
 }
 #[test]
 fn bindgen_test_layout_UnionWithDtor() {

tests/expectations/tests/union_fields.rs

@@ -10,6 +10,7 @@ pub union nsStyleUnion {
     pub mInt: ::std::os::raw::c_int,
     pub mFloat: f32,
     pub mPointer: *mut ::std::os::raw::c_void,
+    _bindgen_union_align: u64,
 }
 #[test]
 fn bindgen_test_layout_nsStyleUnion() {

tests/expectations/tests/union_template.rs

@@ -14,6 +14,7 @@ pub struct NastyStruct {
 pub union NastyStruct__bindgen_ty_1 {
     pub mFoo: *mut ::std::os::raw::c_void,
     pub mDummy: ::std::os::raw::c_ulong,
+    _bindgen_union_align: u64,
 }
 impl Default for NastyStruct__bindgen_ty_1 {
     fn default() -> Self { unsafe { ::std::mem::zeroed() } }
@@ -22,6 +23,7 @@ impl Default for NastyStruct__bindgen_ty_1 {
 pub union NastyStruct__bindgen_ty_2 {
     pub wat: ::std::os::raw::c_short,
     pub wut: *mut ::std::os::raw::c_int,
+    _bindgen_union_align: u64,
 }
 impl Default for NastyStruct__bindgen_ty_2 {
     fn default() -> Self { unsafe { ::std::mem::zeroed() } }
@@ -33,6 +35,7 @@ impl Default for NastyStruct {
 pub union Whatever {
     pub mTPtr: *mut ::std::os::raw::c_void,
     pub mInt: ::std::os::raw::c_int,
+    _bindgen_union_align: u64,
 }
 impl Default for Whatever {
     fn default() -> Self { unsafe { ::std::mem::zeroed() } }

tests/expectations/tests/union_with_anon_struct.rs

@@ -8,6 +8,7 @@
 #[derive(Copy)]
 pub union foo {
     pub bar: foo__bindgen_ty_1,
+    _bindgen_union_align: [u32; 2usize],
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]

tests/expectations/tests/union_with_anon_struct_bitfield.rs

@@ -9,6 +9,7 @@
 pub union foo {
     pub a: ::std::os::raw::c_int,
     pub __bindgen_anon_1: foo__bindgen_ty_1,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]

tests/expectations/tests/union_with_anon_union.rs

@@ -8,12 +8,14 @@
 #[derive(Copy)]
 pub union foo {
     pub bar: foo__bindgen_ty_1,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Copy)]
 pub union foo__bindgen_ty_1 {
     pub a: ::std::os::raw::c_uint,
     pub b: ::std::os::raw::c_ushort,
+    _bindgen_union_align: u32,
 }
 #[test]
 fn bindgen_test_layout_foo__bindgen_ty_1() {

tests/expectations/tests/union_with_anon_unnamed_struct.rs

@@ -9,6 +9,7 @@
 pub union pixel {
     pub rgba: ::std::os::raw::c_uint,
     pub __bindgen_anon_1: pixel__bindgen_ty_1,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Debug, Default, Copy, Hash)]

tests/expectations/tests/union_with_anon_unnamed_union.rs

@@ -9,12 +9,14 @@
 pub union foo {
     pub a: ::std::os::raw::c_uint,
     pub __bindgen_anon_1: foo__bindgen_ty_1,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Copy)]
 pub union foo__bindgen_ty_1 {
     pub b: ::std::os::raw::c_ushort,
     pub c: ::std::os::raw::c_uchar,
+    _bindgen_union_align: u16,
 }
 #[test]
 fn bindgen_test_layout_foo__bindgen_ty_1() {

tests/expectations/tests/union_with_big_member.rs

@@ -9,6 +9,7 @@
 pub union WithBigArray {
     pub a: ::std::os::raw::c_int,
     pub b: [::std::os::raw::c_int; 33usize],
+    _bindgen_union_align: [u32; 33usize],
 }
 #[test]
 fn bindgen_test_layout_WithBigArray() {
@@ -38,6 +39,7 @@ impl Default for WithBigArray {
 pub union WithBigArray2 {
     pub a: ::std::os::raw::c_int,
     pub b: [::std::os::raw::c_char; 33usize],
+    _bindgen_union_align: [u32; 9usize],
 }
 #[test]
 fn bindgen_test_layout_WithBigArray2() {
@@ -67,6 +69,7 @@ impl Default for WithBigArray2 {
 pub union WithBigMember {
     pub a: ::std::os::raw::c_int,
     pub b: WithBigArray,
+    _bindgen_union_align: [u32; 33usize],
 }
 #[test]
 fn bindgen_test_layout_WithBigMember() {

tests/expectations/tests/union_with_nesting.rs

@@ -9,6 +9,7 @@
 pub union foo {
     pub a: ::std::os::raw::c_uint,
     pub __bindgen_anon_1: foo__bindgen_ty_1,
+    _bindgen_union_align: u32,
 }
 #[repr(C)]
 #[derive(Copy)]
@@ -21,6 +22,7 @@ pub struct foo__bindgen_ty_1 {
 pub union foo__bindgen_ty_1__bindgen_ty_1 {
     pub b1: ::std::os::raw::c_ushort,
     pub b2: ::std::os::raw::c_ushort,
+    _bindgen_union_align: u16,
 }
 #[test]
 fn bindgen_test_layout_foo__bindgen_ty_1__bindgen_ty_1() {
@@ -56,6 +58,7 @@ impl Default for foo__bindgen_ty_1__bindgen_ty_1 {
 pub union foo__bindgen_ty_1__bindgen_ty_2 {
     pub c1: ::std::os::raw::c_ushort,
     pub c2: ::std::os::raw::c_ushort,
+    _bindgen_union_align: u16,
 }
 #[test]
 fn bindgen_test_layout_foo__bindgen_ty_1__bindgen_ty_2() {

tests/expectations/tests/use-core.rs

@@ -45,6 +45,7 @@ impl Default for foo {
 pub union _bindgen_ty_1 {
     pub bar: ::std::os::raw::c_int,
     pub baz: ::std::os::raw::c_long,
+    _bindgen_union_align: u64,
 }
 #[test]
 fn bindgen_test_layout__bindgen_ty_1() {