[Clang] Export inline move constructors in dllexport-ed template instantiations on non-MSVC targets

[kikairoya]

Previously, even when MSVC compatibility was not requested, inline move constructors in dllexport-ed templates were not exported, which was seemingly unintended.
On non-MSVC targets (MinGW, Cygwin, and PS), such move constructors should be exported consistently with copy constructors and with the behavior of modern MSVC.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Tomohiro Kashiwada (kikairoya)

Changes

Previously, even when MSVC compatibility was not requested, inline move constructors in dllexport-ed templates were not exported, which was seemingly unintended.
On non-MSVC targets (MinGW, Cygwin, and PS), such move constructors should be exported consistently with copy constructors and with the behavior of modern MSVC.

---

Full diff: https://github.com/llvm/llvm-project/pull/168170.diff

3 Files Affected:

• (modified) clang/lib/Sema/SemaDeclCXX.cpp (+1)
• (modified) clang/test/CodeGenCXX/dllexport.cpp (+1)
• (modified) clang/test/CodeGenCXX/mingw-template-dllexport.cpp (+2)

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index aa36a79142e52..5f741166d0e29 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -6627,6 +6627,7 @@ void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
         auto *Ctor = dyn_cast<CXXConstructorDecl>(MD);
         if ((MD->isMoveAssignmentOperator() ||
              (Ctor && Ctor->isMoveConstructor())) &&
+            getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2010) &&
             !getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015))
           continue;
 
diff --git a/clang/test/CodeGenCXX/dllexport.cpp b/clang/test/CodeGenCXX/dllexport.cpp
index ef9d8131c511c..a34a87c5b9f21 100644
--- a/clang/test/CodeGenCXX/dllexport.cpp
+++ b/clang/test/CodeGenCXX/dllexport.cpp
@@ -1131,5 +1131,6 @@ class __declspec(dllexport) ACE_Shared_Object {
 class __declspec(dllexport) ACE_Service_Object : public ACE_Shared_Object {};
 // Implicit move constructor declaration.
 // MSVC2015-DAG: define weak_odr dso_local dllexport {{.+}}ACE_Service_Object@@Q{{.+}}@$$Q
+// PS-DAG: define weak_odr dllexport void @_ZN18ACE_Service_ObjectC1EOS_
 // The declarations should not be exported.
 // MSVC2013-NOT: define weak_odr dso_local dllexport {{.+}}ACE_Service_Object@@Q{{.+}}@$$Q
diff --git a/clang/test/CodeGenCXX/mingw-template-dllexport.cpp b/clang/test/CodeGenCXX/mingw-template-dllexport.cpp
index de112d6da53db..15969d2415cca 100644
--- a/clang/test/CodeGenCXX/mingw-template-dllexport.cpp
+++ b/clang/test/CodeGenCXX/mingw-template-dllexport.cpp
@@ -10,11 +10,13 @@
 
 template <class T>
 class c {
+  c(c &&) noexcept {}
   void f() {}
 };
 
 template class __declspec(dllexport) c<int>;
 
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiEC1EOS0_
 // CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiE1fEv
 
 extern template class __declspec(dllexport) c<char>;

[kikairoya]

cc: @mstorsjo @jmorse

[jmorse]

@bd1976bris @playstation-edd this feels harmless to me (exporting inline move-constructors and move-operators where we already do it for normal copy ones?) , however I'm no expert on dllexport and friends. Opinions please!