From dd6330a57361bac38e4a4e7743852955add22128 Mon Sep 17 00:00:00 2001
From: yamachu <yamachu.dev@gmail.com>
Date: Wed, 6 Sep 2023 19:30:21 +0900
Subject: [PATCH 1/2] treat and parse structs without repr attributes as unit
 structs

---
 csbindgen/src/parser.rs | 53 ++++++++++++++++++++++++++++-------------
 1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/csbindgen/src/parser.rs b/csbindgen/src/parser.rs
index bdfba17..8928798 100644
--- a/csbindgen/src/parser.rs
+++ b/csbindgen/src/parser.rs
@@ -170,23 +170,42 @@ pub fn collect_struct(ast: &syn::File, result: &mut Vec<RustStruct>) {
                 is_union: true,
             });
         } else if let Item::Struct(t) = item {
-            if let syn::Fields::Named(f) = &t.fields {
-                let struct_name = t.ident.to_string();
-                let fields = collect_fields(f);
-                result.push(RustStruct {
-                    struct_name,
-                    fields,
-                    is_union: false,
-                });
-            } else if let syn::Fields::Unnamed(f) = &t.fields {
-                let struct_name = t.ident.to_string();
-                let fields = collect_fields_unnamed(f);
-                result.push(RustStruct {
-                    struct_name,
-                    fields,
-                    is_union: false,
-                });
-            } else if let syn::Fields::Unit = &t.fields {
+            let mut repr = None;
+            for attr in &t.attrs {
+                let last_segment = attr.path.segments.last().unwrap();
+                if last_segment.ident == "repr" {
+                    repr = Some(attr.tokens.to_string());
+                }
+            }
+
+            if let Some(_) = repr {
+                if let syn::Fields::Named(f) = &t.fields {
+                    let struct_name = t.ident.to_string();
+                    let fields = collect_fields(f);
+                    result.push(RustStruct {
+                        struct_name,
+                        fields,
+                        is_union: false,
+                    });
+                } else if let syn::Fields::Unnamed(f) = &t.fields {
+                    let struct_name = t.ident.to_string();
+                    let fields = collect_fields_unnamed(f);
+                    result.push(RustStruct {
+                        struct_name,
+                        fields,
+                        is_union: false,
+                    });
+                } else if let syn::Fields::Unit = &t.fields {
+                    let struct_name = t.ident.to_string();
+                    let fields: Vec<FieldMember> = Vec::new();
+                    result.push(RustStruct {
+                        struct_name,
+                        fields,
+                        is_union: false,
+                    });
+                }
+            } else {
+                // non #[repr(?)] struct, treat as Unit struct
                 let struct_name = t.ident.to_string();
                 let fields: Vec<FieldMember> = Vec::new();
                 result.push(RustStruct {

From c27e01bd905352d3973fd47635ef73917866e15c Mon Sep 17 00:00:00 2001
From: yamachu <yamachu.dev@gmail.com>
Date: Wed, 6 Sep 2023 19:35:34 +0900
Subject: [PATCH 2/2] Add sample case

---
 csbindgen-tests/src/lib.rs      | 14 ++++++++++++++
 dotnet-sandbox/NativeMethods.cs | 11 +++++++++++
 2 files changed, 25 insertions(+)

diff --git a/csbindgen-tests/src/lib.rs b/csbindgen-tests/src/lib.rs
index 4983013..0b91338 100644
--- a/csbindgen-tests/src/lib.rs
+++ b/csbindgen-tests/src/lib.rs
@@ -606,6 +606,20 @@ pub struct CallbackTable {
     pub foobar: extern "C" fn(i: i32) -> i32,
 }
 
+pub struct InternalHiddenContext {
+    pub a: i32
+}
+
+pub struct TreatAsEmptyStruct {
+    internal: std::sync::Arc<InternalHiddenContext>
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn init_treat_as_empty_struct_context(_out: NonNull<Box<TreatAsEmptyStruct>>) {}
+
+#[no_mangle]
+pub unsafe extern "C" fn free_treat_as_empty_struct_context(_src: *mut TreatAsEmptyStruct) {}
+
 // fn run_physix(){
 //     unsafe {
 //         let foundation = physx_create_foundation();
diff --git a/dotnet-sandbox/NativeMethods.cs b/dotnet-sandbox/NativeMethods.cs
index 01e7a4b..0003c51 100644
--- a/dotnet-sandbox/NativeMethods.cs
+++ b/dotnet-sandbox/NativeMethods.cs
@@ -176,6 +176,12 @@ namespace CsBindgen
         [DllImport(__DllName, EntryPoint = "call_bindgen_lz4", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
         public static extern void call_bindgen_lz4();
 
+        [DllImport(__DllName, EntryPoint = "init_treat_as_empty_struct_context", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern void init_treat_as_empty_struct_context(TreatAsEmptyStruct** _out);
+
+        [DllImport(__DllName, EntryPoint = "free_treat_as_empty_struct_context", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern void free_treat_as_empty_struct_context(TreatAsEmptyStruct* _src);
+
 
     }
 
@@ -260,6 +266,11 @@ namespace CsBindgen
         public delegate* unmanaged[Cdecl]<int, int> foobar;
     }
 
+    [StructLayout(LayoutKind.Sequential)]
+    internal unsafe partial struct TreatAsEmptyStruct
+    {
+    }
+
 
     [Flags]
     internal enum EnumFlags : uint