Fix BitfieldUnit constructor to handle 64 bit wide bitfields on 32 bit.

Fixes #1639.

Author: heycam

src/codegen/mod.rs

@@ -1200,12 +1200,8 @@ impl BitfieldUnit {
 
 impl Bitfield {
     /// Extend an under construction bitfield unit constructor with this
-    /// bitfield. This involves two things:
-    ///
-    /// 1. Adding a parameter with this bitfield's name and its type.
-    ///
-    /// 2. Setting the relevant bits on the `__bindgen_bitfield_unit` variable
-    ///    that's being constructed.
+    /// bitfield. This sets the relevant bits on the `__bindgen_bitfield_unit`
+    /// variable that's being constructed.
     fn extend_ctor_impl(
         &self,
         ctx: &BindgenContext,
@@ -1216,7 +1212,9 @@ impl Bitfield {
         let bitfield_ty_layout = bitfield_ty
             .layout(ctx)
             .expect("Bitfield without layout? Gah!");
-        let bitfield_int_ty = helpers::blob(ctx, bitfield_ty_layout);
+        let bitfield_int_ty = helpers::integer_type(ctx, bitfield_ty_layout)
+            .expect("Should already have verified that the bitfield is \
+                     representable as an int");
 
         let offset = self.offset_into_unit();
         let width = self.width() as u8;

tests/expectations/tests/bitfield-linux-32.rs

@@ -0,0 +1,147 @@
+/* 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, packed(4))]
+#[repr(align(4))]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct Test {
+    pub _bitfield_1: __BindgenBitfieldUnit<[u8; 8usize], u64>,
+}
+#[test]
+fn bindgen_test_layout_Test() {
+    assert_eq!(
+        ::std::mem::size_of::<Test>(),
+        8usize,
+        concat!("Size of: ", stringify!(Test))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<Test>(),
+        4usize,
+        concat!("Alignment of ", stringify!(Test))
+    );
+}
+impl Test {
+    #[inline]
+    pub fn x(&self) -> u64 {
+        unsafe { ::std::mem::transmute(self._bitfield_1.get(0usize, 56u8) as u64) }
+    }
+    #[inline]
+    pub fn set_x(&mut self, val: u64) {
+        unsafe {
+            let val: u64 = ::std::mem::transmute(val);
+            self._bitfield_1.set(0usize, 56u8, val as u64)
+        }
+    }
+    #[inline]
+    pub fn y(&self) -> u64 {
+        unsafe { ::std::mem::transmute(self._bitfield_1.get(56usize, 8u8) as u64) }
+    }
+    #[inline]
+    pub fn set_y(&mut self, val: u64) {
+        unsafe {
+            let val: u64 = ::std::mem::transmute(val);
+            self._bitfield_1.set(56usize, 8u8, val as u64)
+        }
+    }
+    #[inline]
+    pub fn new_bitfield_1(x: u64, y: u64) -> __BindgenBitfieldUnit<[u8; 8usize], u64> {
+        let mut __bindgen_bitfield_unit: __BindgenBitfieldUnit<[u8; 8usize], u64> =
+            Default::default();
+        __bindgen_bitfield_unit.set(0usize, 56u8, {
+            let x: u64 = unsafe { ::std::mem::transmute(x) };
+            x as u64
+        });
+        __bindgen_bitfield_unit.set(56usize, 8u8, {
+            let y: u64 = unsafe { ::std::mem::transmute(y) };
+            y as u64
+        });
+        __bindgen_bitfield_unit
+    }
+}

tests/headers/bitfield-linux-32.hpp

@@ -0,0 +1,8 @@
+// bindgen-flags: -- --target=i586-unknown-linux
+
+typedef unsigned long long uint64_t;
+
+struct Test {
+  uint64_t x : 56;
+  uint64_t y : 8;
+};