[MS] Mark default args of exported default constructors as used

Fixes a regression introduced in r291045, which would lead to link errors. While we should no longer encounter unparsed or uninstantiated default arguments in this codepath, we still need to call CheckCXXDefaultArgExpr to mark the default argument expressions as ODR-used. llvm-svn: 291453
llvm · Jan 9, 2017 · 82713bf · 82713bf
1 parent 6615ea8
commit 82713bf
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Showing 2 changed files with 39 additions and 2 deletions.
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -5395,14 +5395,32 @@ static void ReferenceDllExportedMethods(Sema &S, CXXRecordDecl *Class) {
   }
 }
 
-static void checkForMultipleExportedDefaultConstructors(Sema &S, CXXRecordDecl *Class) {
+static void checkForMultipleExportedDefaultConstructors(Sema &S,
+                                                        CXXRecordDecl *Class) {
+  // Only the MS ABI has default constructor closures, so we don't need to do
+  // this semantic checking anywhere else.
+  if (!S.Context.getTargetInfo().getCXXABI().isMicrosoft())
+    return;
+
   CXXConstructorDecl *LastExportedDefaultCtor = nullptr;
   for (Decl *Member : Class->decls()) {
     // Look for exported default constructors.
     auto *CD = dyn_cast<CXXConstructorDecl>(Member);
-    if (!CD || !CD->isDefaultConstructor() || !CD->hasAttr<DLLExportAttr>())
+    if (!CD || !CD->isDefaultConstructor())
+      continue;
+    auto *Attr = CD->getAttr<DLLExportAttr>();
+    if (!Attr)
       continue;
 
+    // If the class is non-dependent, mark the default arguments as ODR-used so
+    // that we can properly codegen the constructor closure.
+    if (!Class->isDependentContext()) {
+      for (ParmVarDecl *PD : CD->parameters()) {
+        (void)S.CheckCXXDefaultArgExpr(Attr->getLocation(), CD, PD);
+        S.DiscardCleanupsInEvaluationContext();
+      }
+    }
+
     if (LastExportedDefaultCtor) {
       S.Diag(LastExportedDefaultCtor->getLocation(),
              diag::err_attribute_dll_ambiguous_default_ctor)

diff --git a/clang/test/CodeGenCXX/dllexport-ctor-closure.cpp b/clang/test/CodeGenCXX/dllexport-ctor-closure.cpp
@@ -61,3 +61,22 @@ struct __declspec(dllexport) NestedOuter {
 
 // CHECK-LABEL: define weak_odr dllexport x86_thiscallcc void @"\01??_FNestedOuter@@QAEXXZ"({{.*}}) {{#[0-9]+}} comdat
 // CHECK-LABEL: define weak_odr dllexport x86_thiscallcc void @"\01??_FNestedInner@NestedOuter@@QAEXXZ"({{.*}}) {{#[0-9]+}} comdat
+
+struct HasDtor {
+  ~HasDtor();
+  int o;
+};
+struct HasImplicitDtor1 { HasDtor o; };
+struct HasImplicitDtor2 { HasDtor o; };
+struct __declspec(dllexport) CtorClosureInline {
+  CtorClosureInline(const HasImplicitDtor1 &v = {}) {}
+};
+struct __declspec(dllexport) CtorClosureOutOfLine {
+  CtorClosureOutOfLine(const HasImplicitDtor2 &v = {});
+};
+CtorClosureOutOfLine::CtorClosureOutOfLine(const HasImplicitDtor2 &v) {}
+
+// CHECK-LABEL: define weak_odr dllexport x86_thiscallcc void @"\01??_FCtorClosureInline@@QAEXXZ"
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01??1HasImplicitDtor1@@QAE@XZ"
+// CHECK-LABEL: define weak_odr dllexport x86_thiscallcc void @"\01??_FCtorClosureOutOfLine@@QAEXXZ"
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01??1HasImplicitDtor2@@QAE@XZ"