From d99de71f1f6b28252592cd51267eb18bb7714181 Mon Sep 17 00:00:00 2001
From: Pierre Avital <pierre.avital@me.com>
Date: Sat, 6 Jul 2024 09:36:23 +0200
Subject: [PATCH] Refine repr support

---
 CHANGELOG.md                 |  3 +++
 Cargo.toml                   |  8 ++++----
 stabby-macros/src/structs.rs | 28 +++++++++++++---------------
 stabby/src/tests/layouts.rs  |  8 ++++++++
 4 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 71e8834..678414a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+# 36.1.1-rc5 (api=2.0.0, abi=2.0.0)
+- Refine support for `#[repr(transparent)]` and `#[repr(align(n))]` in `#[stabby::stabby]` structs up to n=64kiB.
+
 # 36.1.1-rc4 (api=2.0.0, abi=2.0.0)
 - Add support for `#[repr(transparent)]` and `#[repr(align(n))]` in `#[stabby::stabby]` structs up to n=64kiB.
 
diff --git a/Cargo.toml b/Cargo.toml
index 5b1673f..8a260b2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,12 +33,12 @@ license = " EPL-2.0 OR Apache-2.0"
 categories = ["development-tools::ffi", "no-std::no-alloc"]
 repository = "https://github.com/ZettaScaleLabs/stabby"
 readme = "stabby/README.md"
-version = "36.1.1-rc4"                                           # Track
+version = "36.1.1-rc5"                                           # Track
 
 [workspace.dependencies]
-stabby-macros = { path = "./stabby-macros/", version = "36.1.1-rc4", default-features = false } # Track
-stabby-abi = { path = "./stabby-abi/", version = "36.1.1-rc4", default-features = false }       # Track
-stabby = { path = "./stabby/", version = "36.1.1-rc4", default-features = false }               # Track
+stabby-macros = { path = "./stabby-macros/", version = "36.1.1-rc5", default-features = false } # Track
+stabby-abi = { path = "./stabby-abi/", version = "36.1.1-rc5", default-features = false }       # Track
+stabby = { path = "./stabby/", version = "36.1.1-rc5", default-features = false }               # Track
 
 abi_stable = "0.11.0"
 libc = "0.2"
diff --git a/stabby-macros/src/structs.rs b/stabby-macros/src/structs.rs
index 2510268..9fa9fd6 100644
--- a/stabby-macros/src/structs.rs
+++ b/stabby-macros/src/structs.rs
@@ -122,17 +122,15 @@ pub fn stabby(
     let clauses = where_clause.as_ref().map(|w| &w.predicates);
     let mut layout = None;
     let mut report = crate::Report::r#struct(ident.to_string(), version, module);
-    let repr = attrs
-        .iter()
-        .find_map(|attr| {
-            if attr.path.is_ident("repr") {
-                syn::parse2::<AllowedRepr>(attr.tokens.clone()).ok()
-            } else {
-                None
-            }
-        })
-        .unwrap_or(AllowedRepr::C);
-    optimize &= !matches!(repr, AllowedRepr::Align(_));
+    let repr = attrs.iter().find_map(|attr| {
+        if attr.path.is_ident("repr") {
+            syn::parse2::<AllowedRepr>(attr.tokens.clone()).ok()
+        } else {
+            None
+        }
+    });
+    let repr_attr = repr.is_none().then(|| quote! {#[repr(C)]});
+    optimize &= !matches!(repr, Some(AllowedRepr::Align(_)));
     let struct_code = match &fields {
         syn::Fields::Named(fields) => {
             let fields = &fields.named;
@@ -146,7 +144,7 @@ pub fn stabby(
             }
             quote! {
                 #(#attrs)*
-                #repr
+                #repr_attr
                 #vis struct #ident #generics #where_clause {
                     #fields
                 }
@@ -164,14 +162,14 @@ pub fn stabby(
             }
             quote! {
                 #(#attrs)*
-                #repr
+                #repr_attr
                 #vis struct #ident #generics #where_clause (#fields);
             }
         }
         syn::Fields::Unit => {
             quote! {
                 #(#attrs)*
-                #repr
+                #repr_attr
                 #vis struct #ident #generics #where_clause;
             }
         }
@@ -179,7 +177,7 @@ pub fn stabby(
     let layout = layout.map_or_else(
         || quote!(()),
         |layout| {
-            if let AllowedRepr::Align(mut n) = repr {
+            if let Some(AllowedRepr::Align(mut n)) = repr {
                 let mut align = quote!(#st::U1);
                 while n > 1 {
                     n /= 2;
diff --git a/stabby/src/tests/layouts.rs b/stabby/src/tests/layouts.rs
index 9ef6e48..3e28b79 100644
--- a/stabby/src/tests/layouts.rs
+++ b/stabby/src/tests/layouts.rs
@@ -127,6 +127,12 @@ pub struct EndPadding {
     a: usize,
     b: u8,
 }
+#[allow(dead_code)]
+#[stabby::stabby]
+#[repr(transparent)]
+pub struct Transparent {
+    a: usize,
+}
 
 #[test]
 fn layouts() {
@@ -255,6 +261,8 @@ fn layouts() {
         3 * 16
     );
     let _ = Align1024::ID;
+    let _: U1024 = <Align1024 as IStable>::Align::default();
+    let _: U1024 = <Align1024 as IStable>::Size::default();
 }
 
 #[allow(dead_code)]