[PATCH] D130331: [C++20] [Modules] Disable preferred_name when writing a C++20 Module interface

[Chuanqi Xu via Phabricator via cfe-commits]

ChuanqiXu created this revision.
ChuanqiXu added reviewers: erichkeane, tahonermann, aaron.ballman.
ChuanqiXu added a project: clang-modules.
Herald added a project: All.
ChuanqiXu requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

This is an alternative to D129748 <https://reviews.llvm.org/D129748>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D130331

Files:
  clang/include/clang/Serialization/ASTWriter.h
  clang/lib/Serialization/ASTReaderDecl.cpp
  clang/lib/Serialization/ASTWriter.cpp
  clang/test/Modules/preferred_name.cppm


Index: clang/test/Modules/preferred_name.cppm
===================================================================
--- /dev/null
+++ clang/test/Modules/preferred_name.cppm
@@ -0,0 +1,39 @@
+// Tests that the ODR check wouldn't produce false-positive result for preferred_name attribute.
+//
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-module-interface -o %t/A.pcm
+// RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t -I%t %t/Use.cppm -verify -fsyntax-only
+//
+//--- foo.h
+template<class _CharT>
+class foo_templ;
+
+typedef foo_templ<char> foo;
+
+template<class _CharT>
+class
+__attribute__((__preferred_name__(foo)))
+foo_templ {
+public:
+    foo_templ() {}
+};
+
+inline foo_templ<char> bar()
+{
+  return foo_templ<char>();
+}
+
+//--- A.cppm
+module;
+#include "foo.h"
+export module A;
+
+//--- Use.cppm
+// expected-no-diagnostics
+module;
+#include "foo.h"
+export module Use;
+import A;
Index: clang/lib/Serialization/ASTWriter.cpp
===================================================================
--- clang/lib/Serialization/ASTWriter.cpp
+++ clang/lib/Serialization/ASTWriter.cpp
@@ -4347,8 +4347,12 @@
 
 void ASTRecordWriter::AddAttr(const Attr *A) {
   auto &Record = *this;
-  if (!A)
+  // FIXME: Clang can't handle the serialization/deserialization of
+  // preferred_name properly now. See
+  // https://github.com/llvm/llvm-project/issues/56490 for example.
+  if (!A || (isa<PreferredNameAttr>(A) && Writer->isWritingNamedModules()))
     return Record.push_back(0);
+
   Record.push_back(A->getKind() + 1); // FIXME: stable encoding, target attrs
 
   Record.AddIdentifierRef(A->getAttrName());
Index: clang/lib/Serialization/ASTReaderDecl.cpp
===================================================================
--- clang/lib/Serialization/ASTReaderDecl.cpp
+++ clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2922,7 +2922,8 @@
 /// Reads attributes from the current stream position.
 void ASTRecordReader::readAttributes(AttrVec &Attrs) {
   for (unsigned I = 0, E = readInt(); I != E; ++I)
-    Attrs.push_back(readAttr());
+    if (auto *Attr = readAttr())
+      Attrs.push_back(Attr);
 }
 
 //===----------------------------------------------------------------------===//
Index: clang/include/clang/Serialization/ASTWriter.h
===================================================================
--- clang/include/clang/Serialization/ASTWriter.h
+++ clang/include/clang/Serialization/ASTWriter.h
@@ -703,6 +703,10 @@
   bool hasChain() const { return Chain; }
   ASTReader *getChain() const { return Chain; }
 
+  bool isWritingNamedModules() const {
+    return WritingModule && WritingModule->isModulePurview();
+  }
+
 private:
   // ASTDeserializationListener implementation
   void ReaderInitialized(ASTReader *Reader) override;


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