Support #[repr(packed(N))] on Rust 1.33+

Fixes https://github.com/rust-lang/rust-bindgen/issues/537.

4 files changed, 25 insertions, 12 deletions

diff --git a/src/codegen/helpers.rs b/src/codegen/helpers.rs
index d6377194..457979b6 100644
--- a/src/codegen/helpers.rs
+++ b/src/codegen/helpers.rs
@@ -7,6 +7,7 @@ use quote::TokenStreamExt;
 
 pub mod attributes {
     use proc_macro2::{Ident, Span, TokenStream};
+    use std::str::FromStr;
 
     pub fn repr(which: &str) -> TokenStream {
         let which = Ident::new(which, Span::call_site());
@@ -16,7 +17,7 @@ pub mod attributes {
     }
 
     pub fn repr_list(which_ones: &[&str]) -> TokenStream {
-        let which_ones = which_ones.iter().cloned().map(|one| Ident::new(one, Span::call_site()));
+        let which_ones = which_ones.iter().cloned().map(|one| TokenStream::from_str(one).expect("repr to be valid"));
         quote! {
             #[repr( #( #which_ones ),* )]
         }
diff --git a/src/codegen/mod.rs b/src/codegen/mod.rs
index 6fd7e7d3..d3395edf 100644
--- a/src/codegen/mod.rs
+++ b/src/codegen/mod.rs
@@ -1673,7 +1673,10 @@ impl CodeGenerator for CompInfo {
             attributes.push(attributes::doc(comment));
         }
         if packed && !is_opaque {
-            attributes.push(attributes::repr_list(&["C", "packed"]));
+            let n = layout.map_or(1, |l| l.align);
+            assert!(ctx.options().rust_features().repr_packed_n || n == 1);
+            let packed_repr = if n == 1 { "packed".to_string() } else { format!("packed({})", n) };
+            attributes.push(attributes::repr_list(&["C", &packed_repr]));
         } else {
             attributes.push(attributes::repr("C"));
         }
diff --git a/src/features.rs b/src/features.rs
index 1f700039..b5a63402 100644
--- a/src/features.rs
+++ b/src/features.rs
@@ -102,6 +102,8 @@ macro_rules! rust_target_base {
             => Stable_1_27 => 1.27;
             /// Rust stable 1.28
             => Stable_1_28 => 1.28;
+            /// Rust stable 1.33
+            => Stable_1_33 => 1.33;
             /// Nightly rust
             => Nightly => nightly;
         );
@@ -190,6 +192,10 @@ rust_feature_def!(
         /// repr(transparent) ([PR](https://github.com/rust-lang/rust/pull/51562))
         => repr_transparent;
     }
+    Stable_1_33 {
+        /// repr(packed(N)) ([PR](https://github.com/rust-lang/rust/pull/57049))
+        => repr_packed_n;
+    }
     Nightly {
         /// `thiscall` calling convention ([Tracking issue](https://github.com/rust-lang/rust/issues/42202))
         => thiscall_abi;
diff --git a/src/ir/comp.rs b/src/ir/comp.rs
index fd4c8274..12a8fa32 100644
--- a/src/ir/comp.rs
+++ b/src/ir/comp.rs
@@ -1649,16 +1649,19 @@ impl IsOpaque for CompInfo {
             return true;
         }
 
-        // We don't have `#[repr(packed = "N")]` in Rust yet, so the best we can
-        // do is make this struct opaque.
-        //
-        // See https://github.com/rust-lang-nursery/rust-bindgen/issues/537 and
-        // https://github.com/rust-lang/rust/issues/33158
-        if self.is_packed(ctx, layout) && layout.map_or(false, |l| l.align > 1) {
-            warn!("Found a type that is both packed and aligned to greater than \
-                   1; Rust doesn't have `#[repr(packed = \"N\")]` yet, so we \
-                   are treating it as opaque");
-            return true;
+        if !ctx.options().rust_features().repr_packed_n {
+            // If we don't have `#[repr(packed(N)]`, the best we can
+            // do is make this struct opaque.
+            //
+            // See https://github.com/rust-lang-nursery/rust-bindgen/issues/537 and
+            // https://github.com/rust-lang/rust/issues/33158
+            if self.is_packed(ctx, layout) && layout.map_or(false, |l| l.align > 1) {
+                warn!("Found a type that is both packed and aligned to greater than \
+                       1; Rust before version 1.33 doesn't have `#[repr(packed(N))]`, so we \
+                       are treating it as opaque. You may wish to set bindgen's rust target \
+                       version to 1.33 or later to enable `#[repr(packed(N))]` support.");
+                return true;
+            }
         }
 
         false