[PATCH] D115610: [C++20] [Modules] Don't create multiple global module fragment

[Chuanqi Xu via Phabricator via cfe-commits]

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

Since the serialization code would recognize modules by names and the name of all global module fragment is `<global>`, so that the serialization code would complain for the same module.

This patch fixes this by using a global module fragment cache in Sema. Before this patch, the compiler would fail on an assertion complaining the duplicated modules.

Test Plan: check-all, an internal module library


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D115610

Files:
  clang/include/clang/Sema/Sema.h
  clang/lib/Sema/SemaModule.cpp
  clang/test/CXX/module/module.unit/p7/Inputs/h8.h
  clang/test/CXX/module/module.unit/p7/Inputs/m8.cppm
  clang/test/CXX/module/module.unit/p7/t8.cpp


Index: clang/test/CXX/module/module.unit/p7/t8.cpp
===================================================================
--- /dev/null
+++ clang/test/CXX/module/module.unit/p7/t8.cpp
@@ -0,0 +1,7 @@
+// RUN: rm -fr %t
+// RUN: mkdir %t
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %S/Inputs/m8.cppm -I%S/Inputs -o %t/m8.pcm
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface -I%S/Inputs/ -fprebuilt-module-path=%t %s -verify
+// expected-no-diagnostics
+export module t8;
+import m8;
Index: clang/test/CXX/module/module.unit/p7/Inputs/m8.cppm
===================================================================
--- /dev/null
+++ clang/test/CXX/module/module.unit/p7/Inputs/m8.cppm
@@ -0,0 +1,8 @@
+module;
+#include "h8.h"
+export module m8;
+
+extern "C++" {
+    void bar();
+}
+
Index: clang/test/CXX/module/module.unit/p7/Inputs/h8.h
===================================================================
--- /dev/null
+++ clang/test/CXX/module/module.unit/p7/Inputs/h8.h
@@ -0,0 +1,4 @@
+#ifndef H8
+#define H8
+void foo();
+#endif
Index: clang/lib/Sema/SemaModule.cpp
===================================================================
--- clang/lib/Sema/SemaModule.cpp
+++ clang/lib/Sema/SemaModule.cpp
@@ -704,19 +704,24 @@
 
 Module *Sema::PushGlobalModuleFragment(SourceLocation BeginLoc,
                                        bool IsImplicit) {
-  ModuleMap &Map = PP.getHeaderSearchInfo().getModuleMap();
-  Module *GlobalModule =
-      Map.createGlobalModuleFragmentForModuleUnit(BeginLoc, getCurrentModule());
-  assert(GlobalModule && "module creation should not fail");
+  // We shouldn't create new global module fragment if there is already
+  // one.
+  if (!GlobalModuleFragmentCache) {
+    ModuleMap &Map = PP.getHeaderSearchInfo().getModuleMap();
+    GlobalModuleFragmentCache = Map.createGlobalModuleFragmentForModuleUnit(
+        BeginLoc, getCurrentModule());
+  }
+
+  assert(GlobalModuleFragmentCache && "module creation should not fail");
 
   // Enter the scope of the global module.
-  ModuleScopes.push_back({BeginLoc, GlobalModule,
+  ModuleScopes.push_back({BeginLoc, GlobalModuleFragmentCache,
                           /*ModuleInterface=*/false,
                           /*ImplicitGlobalModuleFragment=*/IsImplicit,
-                          /*VisibleModuleSet*/{}});
-  VisibleModules.setVisible(GlobalModule, BeginLoc);
+                          /*VisibleModuleSet*/ {}});
+  VisibleModules.setVisible(GlobalModuleFragmentCache, BeginLoc);
 
-  return GlobalModule;
+  return GlobalModuleFragmentCache;
 }
 
 void Sema::PopGlobalModuleFragment() {
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -2213,6 +2213,8 @@
   };
   /// The modules we're currently parsing.
   llvm::SmallVector<ModuleScope, 16> ModuleScopes;
+  /// The gloabl module fragment of the current tranlation unit.
+  clang::Module *GlobalModuleFragmentCache = nullptr;
 
   /// Namespace definitions that we will export when they finish.
   llvm::SmallPtrSet<const NamespaceDecl*, 8> DeferredExportedNamespaces;


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