From 6ceb32a66fb429b1e6880b723c4f0103f00e6dbd Mon Sep 17 00:00:00 2001
From: Chuanqi Xu <yedeng.yd@linux.alibaba.com>
Date: Tue, 7 Mar 2023 15:16:23 +0800
Subject: [PATCH] [C++20] [Modules] Handle the linkage of defaulted friend
 function definition correctly

Close https://github.com/llvm/llvm-project/issues/61067

Previously we will only handle the defaulted member functions as
discardable ODR. But we need to handle defaulted friend function in this
way too. Otherwise we may run into the problems the above issue report
mentions.
---
 clang/lib/AST/ASTContext.cpp    |  5 ++---
 clang/test/Modules/pr61067.cppm | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 3 deletions(-)
 create mode 100644 clang/test/Modules/pr61067.cppm

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index f226832..499009b 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -11625,9 +11625,8 @@ static GVALinkage basicGVALinkageForFunction(const ASTContext &Context,
 
   // Non-user-provided functions get emitted as weak definitions with every
   // use, no matter whether they've been explicitly instantiated etc.
-  if (const auto *MD = dyn_cast<CXXMethodDecl>(FD))
-    if (!MD->isUserProvided())
-      return GVA_DiscardableODR;
+  if (!FD->isUserProvided())
+    return GVA_DiscardableODR;
 
   GVALinkage External;
   switch (FD->getTemplateSpecializationKind()) {
diff --git a/clang/test/Modules/pr61067.cppm b/clang/test/Modules/pr61067.cppm
new file mode 100644
index 0000000..8469a1d
--- /dev/null
+++ b/clang/test/Modules/pr61067.cppm
@@ -0,0 +1,40 @@
+// From https://github.com/llvm/llvm-project/issues/61067
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/a.cppm \
+// RUN:     -emit-module-interface -o %t/a.pcm
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/b.cppm \
+// RUN:     -emit-module-interface -fmodule-file=a=%t/a.pcm -o %t/b.pcm
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/b.pcm -S \
+// RUN:     -emit-llvm -disable-llvm-passes -o - | FileCheck %t/b.cppm
+// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/c.cpp -fmodule-file=a=%t/a.pcm \
+// RUN:     -S -emit-llvm -disable-llvm-passes -o - | FileCheck %t/c.cpp
+
+//--- a.cppm
+export module a;
+
+export struct a {
+	friend bool operator==(a, a) = default;
+};
+
+//--- b.cppm
+export module b;
+
+import a;
+
+void b() {
+	(void)(a() == a());
+}
+
+// CHECK: define{{.*}}linkonce_odr{{.*}}@_ZW1aeqS_1aS0_(
+
+//--- c.cpp
+import a;
+
+int c() {
+    (void)(a() == a());
+}
+
+// CHECK: define{{.*}}linkonce_odr{{.*}}@_ZW1aeqS_1aS0_(
-- 
2.7.4