[clang] 5ee6cff - [clang] Propagate definition data to all redecls (#170090)

[via cfe-commits]

Author: Jonas Hahnfeld
Date: 2025-12-03T09:10:56+01:00
New Revision: 5ee6cff90ba5d8e08066eeeef0c27aa0b6f24d2c

URL: https://github.com/llvm/llvm-project/commit/5ee6cff90ba5d8e08066eeeef0c27aa0b6f24d2c
DIFF: https://github.com/llvm/llvm-project/commit/5ee6cff90ba5d8e08066eeeef0c27aa0b6f24d2c.diff

LOG: [clang] Propagate definition data to all redecls (#170090)

Fix the propagation added in commit 0d490ae55f to include all redecls,
not only previous ones. This fixes another instance of the assertion
"Cannot get layout of forward declarations" in getASTRecordLayout().

Kudos to Alexander Kornienko for providing an initial version of the
reproducer that I further simplified.

Fixes #170084

Added: 
    clang/test/Modules/GH170084.cpp

Modified: 
    clang/lib/Serialization/ASTReaderDecl.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 5456e73956659..882d54f31280a 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2107,8 +2107,8 @@ void ASTDeclMerger::MergeDefinitionData(
     auto *Def = DD.Definition;
     DD = std::move(MergeDD);
     DD.Definition = Def;
-    while ((Def = Def->getPreviousDecl()))
-      cast<CXXRecordDecl>(Def)->DefinitionData = ⅅ
+    for (auto *D : Def->redecls())
+      cast<CXXRecordDecl>(D)->DefinitionData = ⅅ
     return;
   }
 

diff  --git a/clang/test/Modules/GH170084.cpp b/clang/test/Modules/GH170084.cpp
new file mode 100644
index 0000000000000..950499467a6bb
--- /dev/null
+++ b/clang/test/Modules/GH170084.cpp
@@ -0,0 +1,75 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+// RUN: cd %t
+
+// RUN: %clang_cc1 -fmodule-name=stl -fno-cxx-modules -emit-module -fmodules -xc++ stl.cppmap -o stl.pcm
+// RUN: %clang_cc1 -fmodule-name=d -fno-cxx-modules -emit-module -fmodules -fmodule-file=stl.pcm -xc++ d.cppmap -o d.pcm
+// RUN: %clang_cc1 -fmodule-name=b -fno-cxx-modules -emit-module -fmodules -fmodule-file=stl.pcm -xc++ b.cppmap -o b.pcm
+// RUN: %clang_cc1 -fmodule-name=a -fno-cxx-modules -emit-module -fmodules -fmodule-file=stl.pcm -fmodule-file=d.pcm -fmodule-file=b.pcm -xc++ a.cppmap -o a.pcm
+// RUN: %clang_cc1 -fno-cxx-modules -fmodules -fmodule-file=a.pcm -emit-llvm -o /dev/null main.cpp
+
+//--- a.cppmap
+module "a" {
+header "a.h"
+}
+
+//--- a.h
+#include "b.h"
+namespace {
+void a(absl::set<char> c) {
+  absl::set<int> b;
+  c.end();
+  c.contains();
+}
+}  // namespace
+
+//--- b.cppmap
+module "b" {
+header "b.h"
+}
+
+//--- b.h
+#include "c.h"
+void b() { absl::set<char> x; }
+
+//--- c.h
+#include "stl.h"
+namespace absl {
+template <typename>
+class set {
+ public:
+  struct iterator {
+    void u() const;
+  };
+  iterator end() const { return {}; }
+  void contains() const { end().u(); }
+  pair<iterator> e();
+};
+}  // namespace absl
+
+//--- d.cppmap
+module "d" {
+header "d.h"
+}
+
+//--- d.h
+#include "c.h"
+void d() { absl::set<char> x; }
+
+//--- stl.cppmap
+module "stl" {
+header "stl.h"
+}
+
+//--- stl.h
+#ifndef _STL_H_
+#define _STL_H_
+template <class>
+struct pair;
+#endif
+
+//--- main.cpp
+// expected-no-diagnostics
+#include "c.h"
+void f(absl::set<char> o) { o.contains(); }