codegen: Don't skip alignment checks if we support repr align.

Plus fix the check that avoids us generating explicit alignment fields for
structs aligned to more than pointer-size.

Fixes #1291

src/codegen/mod.rs

@@ -1776,8 +1776,9 @@ impl CodeGenerator for CompInfo {
                     let align = layout.align;
 
                     let check_struct_align =
-                        if align > ctx.target_pointer_size() {
-                            // FIXME when [RFC 1358](https://github.com/rust-lang/rust/issues/33626) ready
+                        if align > ctx.target_pointer_size() &&
+                            !ctx.options().rust_features().repr_align
+                        {
                             None
                         } else {
                             Some(quote! {

src/codegen/struct_layout.rs

@@ -286,8 +286,18 @@ impl<'a> StructLayoutTracker<'a> {
     }
 
     pub fn requires_explicit_align(&self, layout: Layout) -> bool {
-        self.max_field_align < layout.align &&
-            layout.align <= self.ctx.target_pointer_size()
+        if self.max_field_align >= layout.align {
+            return false;
+        }
+        // At this point we require explicit alignment, but we may not be able
+        // to generate the right bits, let's double check.
+        if self.ctx.options().rust_features().repr_align {
+            return true;
+        }
+
+        // We can only generate up-to a word of alignment unless we support
+        // repr(align).
+        layout.align <= self.ctx.target_pointer_size()
     }
 
     fn padding_bytes(&self, layout: Layout) -> usize {

tests/expectations/tests/issue-1291.rs

@@ -0,0 +1,179 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]
+
+#[repr(C)]
+#[repr(align(16))]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct RTCRay {
+    pub org: [f32; 3usize],
+    pub align0: f32,
+    pub dir: [f32; 3usize],
+    pub align1: f32,
+    pub tnear: f32,
+    pub tfar: f32,
+    pub time: f32,
+    pub mask: ::std::os::raw::c_uint,
+    pub Ng: [f32; 3usize],
+    pub align2: f32,
+    pub u: f32,
+    pub v: f32,
+    pub geomID: ::std::os::raw::c_uint,
+    pub primID: ::std::os::raw::c_uint,
+    pub instID: ::std::os::raw::c_uint,
+    pub __bindgen_padding_0: [u32; 3usize],
+    pub __bindgen_align: [u8; 0usize],
+}
+#[test]
+fn bindgen_test_layout_RTCRay() {
+    assert_eq!(
+        ::std::mem::size_of::<RTCRay>(),
+        96usize,
+        concat!("Size of: ", stringify!(RTCRay))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<RTCRay>(),
+        16usize,
+        concat!("Alignment of ", stringify!(RTCRay))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).org as *const _ as usize },
+        0usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(org)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).align0 as *const _ as usize },
+        12usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(align0)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).dir as *const _ as usize },
+        16usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(dir)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).align1 as *const _ as usize },
+        28usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(align1)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).tnear as *const _ as usize },
+        32usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(tnear)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).tfar as *const _ as usize },
+        36usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(tfar)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).time as *const _ as usize },
+        40usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(time)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).mask as *const _ as usize },
+        44usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(mask)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).Ng as *const _ as usize },
+        48usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(Ng)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).align2 as *const _ as usize },
+        60usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(align2)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).u as *const _ as usize },
+        64usize,
+        concat!("Offset of field: ", stringify!(RTCRay), "::", stringify!(u))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).v as *const _ as usize },
+        68usize,
+        concat!("Offset of field: ", stringify!(RTCRay), "::", stringify!(v))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).geomID as *const _ as usize },
+        72usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(geomID)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).primID as *const _ as usize },
+        76usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(primID)
+        )
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<RTCRay>())).instID as *const _ as usize },
+        80usize,
+        concat!(
+            "Offset of field: ",
+            stringify!(RTCRay),
+            "::",
+            stringify!(instID)
+        )
+    );
+}

tests/headers/issue-1291.hpp

@@ -0,0 +1,21 @@
+// bindgen-flags: --rust-target 1.25
+// bindgen-unstable
+
+struct __attribute__((aligned(16))) RTCRay
+    {
+  float org[3];
+  float align0;
+  float dir[3];
+  float align1;
+  float tnear;
+  float tfar;
+  float time;
+  unsigned mask;
+  float Ng[3];
+  float align2;
+  float u;
+  float v;
+  unsigned geomID;
+  unsigned primID;
+  unsigned instID;
+};