From df65599b1f95852192c66adb15da073d5ee280f8 Mon Sep 17 00:00:00 2001
From: Putta Khunchalee <ultimaweapon@outlook.com>
Date: Thu, 17 Oct 2024 23:51:40 +0700
Subject: [PATCH] Adds cppbind::type_info::align

---
 cppbind.hpp           |  4 +++-
 macros/src/cpp.rs     | 16 ++++++++++++++--
 macros/src/meta.rs    |  6 ++++++
 macros/src/meta/ty.rs |  1 +
 4 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/cppbind.hpp b/cppbind.hpp
index 5878097..3c110b2 100644
--- a/cppbind.hpp
+++ b/cppbind.hpp
@@ -5,12 +5,14 @@
 #include <stddef.h>
 
 #define CPPBIND_CLASS(n) \
-    template<> const size_t cppbind::type_info<n>::size = sizeof(n)
+    template<> const size_t cppbind::type_info<n>::size = sizeof(n); \
+    template<> const size_t cppbind::type_info<n>::align = alignof(n)
 
 namespace cppbind {
     template<typename T>
     struct type_info {
         static const size_t size;
+        static const size_t align;
     };
 }
 
diff --git a/macros/src/cpp.rs b/macros/src/cpp.rs
index 82239bd..e3840c3 100644
--- a/macros/src/cpp.rs
+++ b/macros/src/cpp.rs
@@ -1,6 +1,6 @@
 use self::class::Class;
 use crate::META;
-use proc_macro2::TokenStream;
+use proc_macro2::{Literal, TokenStream};
 use quote::{format_ident, quote};
 use syn::parse::{Parse, ParseStream};
 use syn::Error;
@@ -46,6 +46,17 @@ fn render_class(item: Class) -> syn::Result<TokenStream> {
         }
     };
 
+    // Get alignment.
+    let align = match meta.align {
+        Some(v) => v,
+        None => {
+            return Err(Error::new_spanned(
+                class,
+                format_args!("cppbind::type_info<{name}>::align not found"),
+            ))
+        }
+    };
+
     // Render constructors.
     let mut impls = TokenStream::new();
 
@@ -63,6 +74,7 @@ fn render_class(item: Class) -> syn::Result<TokenStream> {
     }
 
     // Compose.
+    let align = Literal::usize_unsuffixed(align);
     let mem = if name.chars().next().unwrap().is_uppercase() {
         format_ident!("{name}Memory")
     } else {
@@ -81,7 +93,7 @@ fn render_class(item: Class) -> syn::Result<TokenStream> {
         }
 
         #[allow(non_camel_case_types)]
-        #[repr(transparent)]
+        #[repr(C, align(#align))]
         pub struct #mem([::std::mem::MaybeUninit<u8>; #size]);
 
         impl #mem {
diff --git a/macros/src/meta.rs b/macros/src/meta.rs
index e461310..065bc19 100644
--- a/macros/src/meta.rs
+++ b/macros/src/meta.rs
@@ -158,6 +158,12 @@ impl Metadata {
                 .map(|v| usize::from_ne_bytes(v.try_into().unwrap()))
                 .ok_or_else(|| SymbolError::GetDataFailed(index))
                 .map(Some)?;
+        } else if *ty == Segment::Ident("align".into()) {
+            info.align = section
+                .get(off..(off + len))
+                .map(|v| usize::from_ne_bytes(v.try_into().unwrap()))
+                .ok_or_else(|| SymbolError::GetDataFailed(index))
+                .map(Some)?;
         } else {
             return Err(SymbolError::UnknownCppbindSymbol);
         }
diff --git a/macros/src/meta/ty.rs b/macros/src/meta/ty.rs
index 114d4f1..71a3f0d 100644
--- a/macros/src/meta/ty.rs
+++ b/macros/src/meta/ty.rs
@@ -2,4 +2,5 @@
 #[derive(Default)]
 pub struct TypeInfo {
     pub size: Option<usize>,
+    pub align: Option<usize>,
 }