ir: Properly find the layout of incomplete arrays.

So as to not pad stuff incorrectly, or needlessly add extra alignment, for
example.

Fixes #1589

5 files changed, 184 insertions, 2 deletions

diff --git a/src/ir/ty.rs b/src/ir/ty.rs
index f54d4760..625b5f87 100644
--- a/src/ir/ty.rs
+++ b/src/ir/ty.rs
@@ -249,6 +249,12 @@ impl Type {
         self.layout.or_else(|| {
             match self.kind {
                 TypeKind::Comp(ref ci) => ci.layout(ctx),
+                TypeKind::Array(inner, length) if length == 0 => {
+                    Some(Layout::new(
+                        0,
+                        ctx.resolve_type(inner).layout(ctx)?.align,
+                    ))
+                }
                 // FIXME(emilio): This is a hack for anonymous union templates.
                 // Use the actual pointer size!
                 TypeKind::Pointer(..) => {
diff --git a/tests/expectations/tests/incomplete-array-padding.rs b/tests/expectations/tests/incomplete-array-padding.rs
new file mode 100644
index 00000000..5e96bbce
--- /dev/null
+++ b/tests/expectations/tests/incomplete-array-padding.rs
@@ -0,0 +1,173 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(
+    dead_code,
+    non_snake_case,
+    non_camel_case_types,
+    non_upper_case_globals
+)]
+
+#[repr(C)]
+#[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub struct __BindgenBitfieldUnit<Storage, Align> {
+    storage: Storage,
+    align: [Align; 0],
+}
+impl<Storage, Align> __BindgenBitfieldUnit<Storage, Align> {
+    #[inline]
+    pub const fn new(storage: Storage) -> Self {
+        Self { storage, align: [] }
+    }
+}
+impl<Storage, Align> __BindgenBitfieldUnit<Storage, Align>
+where
+    Storage: AsRef<[u8]> + AsMut<[u8]>,
+{
+    #[inline]
+    pub fn get_bit(&self, index: usize) -> bool {
+        debug_assert!(index / 8 < self.storage.as_ref().len());
+        let byte_index = index / 8;
+        let byte = self.storage.as_ref()[byte_index];
+        let bit_index = if cfg!(target_endian = "big") {
+            7 - (index % 8)
+        } else {
+            index % 8
+        };
+        let mask = 1 << bit_index;
+        byte & mask == mask
+    }
+    #[inline]
+    pub fn set_bit(&mut self, index: usize, val: bool) {
+        debug_assert!(index / 8 < self.storage.as_ref().len());
+        let byte_index = index / 8;
+        let byte = &mut self.storage.as_mut()[byte_index];
+        let bit_index = if cfg!(target_endian = "big") {
+            7 - (index % 8)
+        } else {
+            index % 8
+        };
+        let mask = 1 << bit_index;
+        if val {
+            *byte |= mask;
+        } else {
+            *byte &= !mask;
+        }
+    }
+    #[inline]
+    pub fn get(&self, bit_offset: usize, bit_width: u8) -> u64 {
+        debug_assert!(bit_width <= 64);
+        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
+        debug_assert!((bit_offset + (bit_width as usize)) / 8 <= self.storage.as_ref().len());
+        let mut val = 0;
+        for i in 0..(bit_width as usize) {
+            if self.get_bit(i + bit_offset) {
+                let index = if cfg!(target_endian = "big") {
+                    bit_width as usize - 1 - i
+                } else {
+                    i
+                };
+                val |= 1 << index;
+            }
+        }
+        val
+    }
+    #[inline]
+    pub fn set(&mut self, bit_offset: usize, bit_width: u8, val: u64) {
+        debug_assert!(bit_width <= 64);
+        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
+        debug_assert!((bit_offset + (bit_width as usize)) / 8 <= self.storage.as_ref().len());
+        for i in 0..(bit_width as usize) {
+            let mask = 1 << i;
+            let val_bit_is_set = val & mask == mask;
+            let index = if cfg!(target_endian = "big") {
+                bit_width as usize - 1 - i
+            } else {
+                i
+            };
+            self.set_bit(index + bit_offset, val_bit_is_set);
+        }
+    }
+}
+#[repr(C)]
+#[derive(Default)]
+pub struct __IncompleteArrayField<T>(::std::marker::PhantomData<T>, [T; 0]);
+impl<T> __IncompleteArrayField<T> {
+    #[inline]
+    pub const fn new() -> Self {
+        __IncompleteArrayField(::std::marker::PhantomData, [])
+    }
+    #[inline]
+    pub unsafe fn as_ptr(&self) -> *const T {
+        ::std::mem::transmute(self)
+    }
+    #[inline]
+    pub unsafe fn as_mut_ptr(&mut self) -> *mut T {
+        ::std::mem::transmute(self)
+    }
+    #[inline]
+    pub unsafe fn as_slice(&self, len: usize) -> &[T] {
+        ::std::slice::from_raw_parts(self.as_ptr(), len)
+    }
+    #[inline]
+    pub unsafe fn as_mut_slice(&mut self, len: usize) -> &mut [T] {
+        ::std::slice::from_raw_parts_mut(self.as_mut_ptr(), len)
+    }
+}
+impl<T> ::std::fmt::Debug for __IncompleteArrayField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+        fmt.write_str("__IncompleteArrayField")
+    }
+}
+impl<T> ::std::clone::Clone for __IncompleteArrayField<T> {
+    #[inline]
+    fn clone(&self) -> Self {
+        Self::new()
+    }
+}
+#[repr(C)]
+#[derive(Debug)]
+pub struct foo {
+    pub _bitfield_1: __BindgenBitfieldUnit<[u8; 1usize], u8>,
+    pub b: __IncompleteArrayField<*mut ::std::os::raw::c_void>,
+}
+#[test]
+fn bindgen_test_layout_foo() {
+    assert_eq!(
+        ::std::mem::size_of::<foo>(),
+        8usize,
+        concat!("Size of: ", stringify!(foo))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<foo>(),
+        8usize,
+        concat!("Alignment of ", stringify!(foo))
+    );
+}
+impl Default for foo {
+    fn default() -> Self {
+        unsafe { ::std::mem::zeroed() }
+    }
+}
+impl foo {
+    #[inline]
+    pub fn a(&self) -> ::std::os::raw::c_char {
+        unsafe { ::std::mem::transmute(self._bitfield_1.get(0usize, 1u8) as u8) }
+    }
+    #[inline]
+    pub fn set_a(&mut self, val: ::std::os::raw::c_char) {
+        unsafe {
+            let val: u8 = ::std::mem::transmute(val);
+            self._bitfield_1.set(0usize, 1u8, val as u64)
+        }
+    }
+    #[inline]
+    pub fn new_bitfield_1(a: ::std::os::raw::c_char) -> __BindgenBitfieldUnit<[u8; 1usize], u8> {
+        let mut __bindgen_bitfield_unit: __BindgenBitfieldUnit<[u8; 1usize], u8> =
+            Default::default();
+        __bindgen_bitfield_unit.set(0usize, 1u8, {
+            let a: u8 = unsafe { ::std::mem::transmute(a) };
+            a as u64
+        });
+        __bindgen_bitfield_unit
+    }
+}
diff --git a/tests/expectations/tests/layout_align.rs b/tests/expectations/tests/layout_align.rs
index ea41b08f..51fa1d1a 100644
--- a/tests/expectations/tests/layout_align.rs
+++ b/tests/expectations/tests/layout_align.rs
@@ -125,7 +125,6 @@ impl<T> ::std::clone::Clone for __IncompleteArrayField<T> {
     }
 }
 #[repr(C)]
-#[repr(align(8))]
 #[derive(Debug)]
 pub struct rte_kni_fifo {
     ///< Next position to be written
diff --git a/tests/expectations/tests/zero-sized-array.rs b/tests/expectations/tests/zero-sized-array.rs
index a1ad22d6..c0b989c8 100644
--- a/tests/expectations/tests/zero-sized-array.rs
+++ b/tests/expectations/tests/zero-sized-array.rs
@@ -122,7 +122,7 @@ fn bindgen_test_layout_InheritsZeroSizedArray() {
     );
 }
 /// And this should not get an `_address` field either.
-#[repr(C, packed)]
+#[repr(C)]
 #[derive(Debug, Default)]
 pub struct DynamicallySizedArray {
     pub arr: __IncompleteArrayField<::std::os::raw::c_char>,
diff --git a/tests/headers/incomplete-array-padding.h b/tests/headers/incomplete-array-padding.h
new file mode 100644
index 00000000..3fcc4c1a
--- /dev/null
+++ b/tests/headers/incomplete-array-padding.h
@@ -0,0 +1,4 @@
+struct foo {
+  char a : 1;
+  void *b[];
+};