Add support for unions

Closes #20

src/lib.rs

@@ -1353,7 +1353,8 @@ impl<'a, 'v> Visitor<'v> for Generator<'a> {
                 self.test_type(&i.ident.to_string());
             }
 
-            ast::ItemKind::Struct(ref s, ref generics) if public => {
+            ast::ItemKind::Struct(ref s, ref generics) |
+            ast::ItemKind::Union(ref s, ref generics) if public => {
                 self.assert_no_generics(i.ident, generics);
                 let is_c = i.attrs.iter().any(|a| {
                     attr::find_repr_attrs(self.sh, a).iter().any(|a| {

testcrate/src/t1.h

@@ -19,6 +19,11 @@ struct T1Baz {
   struct T1Bar b;
 };
 
+typedef union {
+  uint64_t a;
+  uint32_t b;
+} T1Union;
+
 void T1a(void);
 void* T1b(void);
 void* T1c(void*);

testcrate/src/t1.rs

@@ -27,6 +27,12 @@ pub struct T1Baz {
     pub b: T1Bar,
 }
 
+#[repr(C)]
+pub union T1Union {
+    pub a: u64,
+    pub b: u32,
+}
+
 i! {
     pub const T1C: u32 = 4;
 }

testcrate/src/t2.h

@@ -9,6 +9,11 @@ struct T2Baz {
   uint32_t b;
 };
 
+typedef struct {
+  uint32_t a;
+  int64_t b;
+} T2Union;
+
 static void T2a(void) {}
 
 #define T2C 4

testcrate/src/t2.rs

@@ -11,6 +11,12 @@ pub struct T2Baz {
     pub b: u32,
 }
 
+#[repr(C)]
+pub union T2Union {
+    pub a: u32,
+    pub b: i64,
+}
+
 pub const T2C: i32 = 5;
 
 i! {

testcrate/tests/all.rs

@@ -36,6 +36,9 @@ fn t2() {
         "bad T2a function pointer",
         "bad T2C value at byte 0",
         "bad T2S string",
+        "bad T2Union size",
+        "bad field type b of T2Union",
+        "bad field offset b of T2Union",
     ];
     let mut errors = errors.iter().cloned().collect::<HashSet<_>>();