From: Reid Kleckner <rnk@google.com>
Date: Mon, 9 Jan 2017 17:27:17 +0000 (+0000)
Subject: [MS] Mark default args of exported default constructors as used
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=0982ba044f48b8d0658cdd7ceeacee0b7a614a88;p=clang

[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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291453 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 02b73e9113..a70e16cce1 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/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/test/CodeGenCXX/dllexport-ctor-closure.cpp b/test/CodeGenCXX/dllexport-ctor-closure.cpp
index 24a2ba6bde..4fae7e10e8 100644
--- a/test/CodeGenCXX/dllexport-ctor-closure.cpp
+++ b/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"