[clang] [C++20] [Modules] Fix the duplicated static initializer problem (PR #114193)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-modules

Author: Chuanqi Xu (ChuanqiXu9)

<details>
<summary>Changes</summary>

Reproducer:

```
//--- a.cppm
export module a;
int func();
static int a = func();

//--- a.cpp
import a;
```

The `func()` should only execute once. However, before this patch we will somehow import `static int a` from a.cppm incorrectly and initialize that again.

This is super bad and can introduce serious runtime behaviors.

And also surprisingly, it looks like the root cause of the problem is simply some oversight choosing APIs.

---
Full diff: https://github.com/llvm/llvm-project/pull/114193.diff


2 Files Affected:

- (modified) clang/lib/CodeGen/CodeGenModule.cpp (+2-2) 
- (added) clang/test/Modules/static-initializer.cppm (+18) 


``````````diff
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 2bcca5e85bdfeb..ba376f9ecfacde 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -7146,8 +7146,8 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
     // For C++ standard modules we are done - we will call the module
     // initializer for imported modules, and that will likewise call those for
     // any imports it has.
-    if (CXX20ModuleInits && Import->getImportedOwningModule() &&
-        !Import->getImportedOwningModule()->isModuleMapModule())
+    if (CXX20ModuleInits && Import->getImportedModule() &&
+        Import->getImportedModule()->isNamedModule())
       break;
 
     // For clang C++ module map modules the initializers for sub-modules are
diff --git a/clang/test/Modules/static-initializer.cppm b/clang/test/Modules/static-initializer.cppm
new file mode 100644
index 00000000000000..10d4854ee67fa6
--- /dev/null
+++ b/clang/test/Modules/static-initializer.cppm
@@ -0,0 +1,18 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/a.cppm -emit-module-interface -o %t/a.pcm
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/a.cpp -fmodule-file=a=%t/a.pcm -emit-llvm -o - | FileCheck %t/a.cpp
+
+//--- a.cppm
+export module a;
+int func();
+static int a = func();
+
+//--- a.cpp
+import a;
+
+// CHECK-NOT: internal global
+// CHECK-NOT: __cxx_global_var_init
+

``````````

</details>


https://github.com/llvm/llvm-project/pull/114193