force pad bytes before large align field

2 files changed, 5 insertions, 3 deletions

diff --git a/src/codegen/struct_layout.rs b/src/codegen/struct_layout.rs
index 24938c16..724bef98 100644
--- a/src/codegen/struct_layout.rs
+++ b/src/codegen/struct_layout.rs
@@ -197,7 +197,7 @@ impl<'a, 'ctx> StructLayoutTracker<'a, 'ctx> {
             };
 
             // Otherwise the padding is useless.
-            let need_padding = padding_bytes >= field_layout.align;
+            let need_padding = padding_bytes >= field_layout.align || field_layout.align > mem::size_of::<*mut ()>();
 
             self.latest_offset += padding_bytes;
 
@@ -213,7 +213,7 @@ impl<'a, 'ctx> StructLayoutTracker<'a, 'ctx> {
                 field_layout);
 
             if need_padding && padding_bytes != 0 {
-                Some(Layout::new(padding_bytes, field_layout.align))
+                Some(Layout::new(padding_bytes, cmp::min(field_layout.align, mem::size_of::<*mut ()>())))
             } else {
                 None
             }
@@ -262,6 +262,8 @@ impl<'a, 'ctx> StructLayoutTracker<'a, 'ctx> {
                 Layout::new(padding_bytes, layout.align)
             };
 
+            debug!("pad bytes to struct {}, {:?}", name, layout);
+
             Some(self.padding_field(layout))
         } else {
             None
diff --git a/src/ir/layout.rs b/src/ir/layout.rs
index 38379261..f21a501c 100644
--- a/src/ir/layout.rs
+++ b/src/ir/layout.rs
@@ -38,7 +38,7 @@ impl Layout {
     /// alignment possible.
     pub fn for_size(size: usize) -> Self {
         let mut next_align = 2;
-        while size % next_align == 0 && next_align <= 2 * mem::size_of::<*mut ()>() {
+        while size % next_align == 0 && next_align <= mem::size_of::<*mut ()>() {
             next_align *= 2;
         }
         Layout {