[PATCH] D115132: [C++20] [Modules] Namespace Declaration shouldn't have module linkage

[Chuanqi Xu via Phabricator via cfe-commits]

ChuanqiXu created this revision.
ChuanqiXu added reviewers: rsmith, aaron.ballman, urnathan, hubert.reinterpretcast, erichkeane.
ChuanqiXu added a project: clang.
ChuanqiXu requested review of this revision.
Herald added a subscriber: cfe-commits.

According to https://eel.is/c++draft/basic.namespace.general#2, a namespace declaration shouldn't have a module linkage.

Further more, without this patch, the compiler would crash for the test in assertion enabled build due to inconsistent linkage for redeclaration for namespaces.

Test Plan: check-all


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D115132

Files:
  clang/lib/AST/Decl.cpp
  clang/test/CXX/basic/basic.namespace/basic.namespace.general/Inputs/p2.cppm
  clang/test/CXX/basic/basic.namespace/basic.namespace.general/Inputs/p2.h
  clang/test/CXX/basic/basic.namespace/basic.namespace.general/p2.cppm


Index: clang/test/CXX/basic/basic.namespace/basic.namespace.general/p2.cppm
===================================================================
--- /dev/null
+++ clang/test/CXX/basic/basic.namespace/basic.namespace.general/p2.cppm
@@ -0,0 +1,14 @@
+// Check that the compiler wouldn't crash due to inconsistent namesapce linkage
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: %clang -std=c++20 %S/Inputs/p2.cppm --precompile -o %t/Y.pcm
+// RUN: %clang -std=c++20 -fprebuilt-module-path=%t -I%S/Inputs %s -c -Xclang -verify
+// expected-no-diagnostics
+export module X;
+import Y;
+
+export namespace foo {
+namespace bar{
+    void baz();
+}
+}
Index: clang/test/CXX/basic/basic.namespace/basic.namespace.general/Inputs/p2.h
===================================================================
--- /dev/null
+++ clang/test/CXX/basic/basic.namespace/basic.namespace.general/Inputs/p2.h
@@ -0,0 +1,7 @@
+#ifndef P2_H
+#define P2_H
+namespace foo {
+namespace bar {
+}
+} // namespace foo
+#endif
Index: clang/test/CXX/basic/basic.namespace/basic.namespace.general/Inputs/p2.cppm
===================================================================
--- /dev/null
+++ clang/test/CXX/basic/basic.namespace/basic.namespace.general/Inputs/p2.cppm
@@ -0,0 +1,7 @@
+module;
+#include "p2.h"
+export module Y;
+export namespace foo {
+// We need to export something at least
+void print();
+}
Index: clang/lib/AST/Decl.cpp
===================================================================
--- clang/lib/AST/Decl.cpp
+++ clang/lib/AST/Decl.cpp
@@ -604,8 +604,14 @@
   //   - A name declared at namespace scope that does not have internal linkage
   //     by the previous rules and that is introduced by a non-exported
   //     declaration has module linkage.
-  if (isInModulePurview(D) && !isExportedFromModuleInterfaceUnit(
-                                  cast<NamedDecl>(D->getCanonicalDecl())))
+  //
+  // [basic.namespace.general]/p2
+  //   A namespace is never attached to a named module and never has a name with
+  //   module linkage.
+  if (isInModulePurview(D) &&
+      !isExportedFromModuleInterfaceUnit(
+          cast<NamedDecl>(D->getCanonicalDecl())) &&
+      !isa<NamespaceDecl>(D))
     return LinkageInfo(ModuleLinkage, DefaultVisibility, false);
 
   return LinkageInfo::external();


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