codegen: support repr(align).

Fixes #917

2 files changed, 24 insertions, 0 deletions

diff --git a/src/codegen/mod.rs b/src/codegen/mod.rs
index 1801520a..950708a0 100644
--- a/src/codegen/mod.rs
+++ b/src/codegen/mod.rs
@@ -1527,6 +1527,7 @@ impl CodeGenerator for CompInfo {
             });
         }
 
+        let mut explicit_align = None;
         if is_opaque {
             // Opaque item should not have generated methods, fields.
             debug_assert!(fields.is_empty());
@@ -1534,6 +1535,8 @@ impl CodeGenerator for CompInfo {
 
             match layout {
                 Some(l) => {
+                    explicit_align = Some(l.align);
+
                     let ty = helpers::blob(l);
                     fields.push(quote! {
                         pub _bindgen_opaque_blob: #ty ,
@@ -1555,6 +1558,7 @@ impl CodeGenerator for CompInfo {
                     if layout.align == 1 {
                         packed = true;
                     } else {
+                        explicit_align = Some(layout.align);
                         let ty = helpers::blob(Layout::new(0, layout.align));
                         fields.push(quote! {
                             pub __bindgen_align: #ty ,
@@ -1637,6 +1641,18 @@ impl CodeGenerator for CompInfo {
             attributes.push(attributes::repr("C"));
         }
 
+        if ctx.options().rust_features().repr_align() {
+            if let Some(explicit) = explicit_align {
+                // Ensure that the struct has the correct alignment even in
+                // presence of alignas.
+                let explicit = helpers::ast_ty::int_expr(explicit as i64);
+                attributes.push(quote! {
+                    #[repr(align(#explicit))]
+                });
+            }
+        }
+
+
         let mut derives = vec![];
         if item.can_derive_debug(ctx) {
             derives.push("Debug");
diff --git a/src/features.rs b/src/features.rs
index d4fbd928..fe4f8453 100644
--- a/src/features.rs
+++ b/src/features.rs
@@ -92,6 +92,8 @@ macro_rules! rust_target_base {
             => Stable_1_19 => 1.19;
             /// Rust stable 1.21
             => Stable_1_21 => 1.21;
+            /// Rust stable 1.24
+            => Stable_1_24 => 1.24;
             /// Nightly rust
             => Nightly => nightly;
         );
@@ -144,6 +146,8 @@ rust_feature_def!(
     => thiscall_abi;
     /// builtin impls for `Clone` ([PR](https://github.com/rust-lang/rust/pull/43690))
     => builtin_clone_impls;
+    /// repr(align) https://github.com/rust-lang/rust/pull/47006
+    => repr_align;
 );
 
 impl From<RustTarget> for RustFeatures {
@@ -158,6 +162,10 @@ impl From<RustTarget> for RustFeatures {
             features.builtin_clone_impls = true;
         }
 
+        if rust_target >= RustTarget::Stable_1_24 {
+            features.repr_align = true;
+        }
+
         if rust_target >= RustTarget::Nightly {
             features.thiscall_abi = true;
         }