Update derives for unions and opaque records (#471)

Author: lucic71

cpp2rust/converter/converter.cpp

@@ -92,10 +92,14 @@ void Converter::EmitGlobalInits(Model model, std::string &out) {
   out += "}\n";
 }
 
-void Converter::EmitOpaqueRecords(std::string &out) {
+void Converter::EmitOpaqueRecords(Model model, std::string &out) {
   record_decls_.ForEachUndefined([&](const std::string &name) {
-    out += "#[derive(Clone, Copy, Default, ByteRepr, VaArg, FnPtrArg)]";
-    out += "#[byte_size(1)]";
+    if (model == Model::kRefCount) {
+      out += "#[derive(Clone, Copy, Default, ByteRepr, VaArg, FnPtrArg)]";
+      out += "#[byte_size(1)]";
+    } else {
+      out += "#[derive(Clone, Copy, Default, VaArg, FnPtrArg)]";
+    }
     out += "pub struct ";
     out += name;
     out += ";\n";
@@ -4250,7 +4254,7 @@ std::string Converter::GetRecordName(const clang::NamedDecl *decl) const {
 std::vector<const char *>
 Converter::GetStructAttributes(const clang::RecordDecl *decl) {
   if (decl->isUnion()) {
-    return {"Copy", "Clone", "FnPtrArg"};
+    return {"Copy", "Clone", "FnPtrArg", "VaArg"};
   }
 
   std::vector<const char *> struct_attrs;

cpp2rust/converter/converter.h

@@ -52,7 +52,7 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
 
   virtual void EmitFilePreamble();
 
-  static void EmitOpaqueRecords(std::string &out);
+  static void EmitOpaqueRecords(Model model, std::string &out);
   static void EmitGlobalInits(Model model, std::string &out);
 
   static void EmitVirtualMethods(std::string &out);

cpp2rust/converter/models/converter_refcount.cpp

@@ -703,6 +703,11 @@ void ConverterRefCount::EmitRustUnion(clang::RecordDecl *decl) {
   RuleRegistry::SetDerives(
       ctx_, ctx_.getCanonicalTagType(decl),
       std::vector<std::string>(attrs.begin(), attrs.end()));
+  StrCat("#[derive(");
+  for (auto *attr : attrs) {
+    StrCat(attr, ',');
+  }
+  StrCat(")]");
 
   auto size = ctx_.getTypeSizeInChars(ctx_.getCanonicalTagType(decl));
   StrCat(std::format(
@@ -2503,7 +2508,7 @@ ConverterRefCount::GetStructAttributes(const clang::RecordDecl *decl) {
   std::vector<const char *> attrs;
 
   if (decl->isUnion()) {
-    return attrs;
+    return {"VaArg", "FnPtrArg"};
   }
 
   if (RecordDerivesClone(decl)) {

cpp2rust/cpp2rust_lib.cpp

@@ -31,7 +31,7 @@ std::string TranspileSrc(std::string_view cc_code, Model model,
                                        rules_dir),
       cc_code, tool_args, std::filesystem::path(filename).filename().string(),
       filename.ends_with(".c") ? CLANG_C_COMPILER : CLANG_CXX_COMPILER);
-  Converter::EmitOpaqueRecords(rs_code);
+  Converter::EmitOpaqueRecords(model, rs_code);
   Converter::EmitVirtualMethods(rs_code);
   if (model == Model::kRefCount) {
     ConverterRefCount::EmitMethodsOnPtr(rs_code);
@@ -76,7 +76,7 @@ std::string TranspileDir(std::string_view build_dir, Model model,
   std::string rs_code;
   FrontendActionFactory factory(rs_code, model, rules_dir);
   Tool.run(&factory);
-  Converter::EmitOpaqueRecords(rs_code);
+  Converter::EmitOpaqueRecords(model, rs_code);
   Converter::EmitVirtualMethods(rs_code);
   if (model == Model::kRefCount) {
     ConverterRefCount::EmitMethodsOnPtr(rs_code);

tests/multi-file/opaque_forward_decl/out/unsafe/opaque_forward_decl.rs

@@ -31,7 +31,6 @@ unsafe fn main_0() -> i32 {
 pub unsafe fn touch_0(mut c: *mut container) {
     &((*c).p);
 }
-#[derive(Clone, Copy, Default, ByteRepr, VaArg, FnPtrArg)]
-#[byte_size(1)]
+#[derive(Clone, Copy, Default, VaArg, FnPtrArg)]
 pub struct opaque;
 pub unsafe fn __cpp2rust_init_globals() {}

tests/unit/out/refcount/tag_vs_identifier_collision.rs

@@ -26,7 +26,7 @@ pub struct point_struct {
     #[offset(4)]
     pub y: i32,
 }
-#[derive(ByteRepr, DeepClone)]
+#[derive(VaArg, FnPtrArg, ByteRepr, DeepClone)]
 #[byte_size(4)]
 pub struct point {
     #[offset(0)]
@@ -48,7 +48,7 @@ impl Default for point {
         }
     }
 }
-#[derive(ByteRepr, DeepClone)]
+#[derive(VaArg, FnPtrArg, ByteRepr, DeepClone)]
 #[byte_size(4)]
 pub struct slot_union {
     #[offset(0)]

tests/unit/out/refcount/union_addrof_external.rs

@@ -29,7 +29,7 @@ impl Default for record {
         }
     }
 }
-#[derive(ByteRepr, DeepClone)]
+#[derive(VaArg, FnPtrArg, ByteRepr, DeepClone)]
 #[byte_size(128)]
 pub struct anon_0 {
     #[offset(0)]

tests/unit/out/refcount/union_basic.rs

@@ -6,7 +6,7 @@ use std::io::prelude::*;
 use std::io::{Read, Seek, Write};
 use std::os::fd::AsFd;
 use std::rc::{Rc, Weak};
-#[derive(ByteRepr, DeepClone)]
+#[derive(VaArg, FnPtrArg, ByteRepr, DeepClone)]
 #[byte_size(4)]
 pub struct basic {
     #[offset(0)]
@@ -28,7 +28,7 @@ impl Default for basic {
         }
     }
 }
-#[derive(ByteRepr, DeepClone)]
+#[derive(VaArg, FnPtrArg, ByteRepr, DeepClone)]
 #[byte_size(1)]
 pub struct empty {
     #[offset(0)]

tests/unit/out/refcount/union_cross_arm_cast.rs

@@ -49,7 +49,7 @@ impl Default for shape_b {
         }
     }
 }
-#[derive(ByteRepr, DeepClone)]
+#[derive(VaArg, FnPtrArg, ByteRepr, DeepClone)]
 #[byte_size(64)]
 pub struct anon_0 {
     #[offset(0)]

tests/unit/out/refcount/union_field_alignment.rs

@@ -6,7 +6,7 @@ use std::io::prelude::*;
 use std::io::{Read, Seek, Write};
 use std::os::fd::AsFd;
 use std::rc::{Rc, Weak};
-#[derive(ByteRepr, DeepClone)]
+#[derive(VaArg, FnPtrArg, ByteRepr, DeepClone)]
 #[byte_size(8)]
 pub struct anon_0 {
     #[offset(0)]