From ad2389cf904e0146e42fcb41f3f4961049ae31e4 Mon Sep 17 00:00:00 2001
From: Shoaib Meenai <smeenai@fb.com>
Date: Fri, 13 Jan 2017 01:28:34 +0000
Subject: [PATCH] [Sema] Restrict explicit instantation definition dllexport

In the case where the template class itself is already `dllexport`, the
implicit instantiation will have already emitted all members. When we
check the explicit instantiation definition, the `Specialization` will
have inherited the `dllexport` attribute, so we'll attempt to emit all
members for a second time, which causes an assertion failure. Restrict
the exporting to when the `dllexport` attribute is newly introduced by
the explicit instantiation definition.

Fixes PR31608.

Differential Revision: https://reviews.llvm.org/D28590

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@291877 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaTemplate.cpp     |  6 ++++--
 test/CodeGenCXX/dllexport.cpp | 20 +++++++++++++++++---
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 7edef7075c..8ad5b5951e 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -7789,6 +7789,7 @@ Sema::ActOnExplicitInstantiation(Scope *S,
   Specialization->setTemplateKeywordLoc(TemplateLoc);
   Specialization->setBraceRange(SourceRange());
 
+  bool PreviouslyDLLExported = Specialization->hasAttr<DLLExportAttr>();
   if (Attr)
     ProcessDeclAttributeList(S, Specialization, Attr);
 
@@ -7851,8 +7852,9 @@ Sema::ActOnExplicitInstantiation(Scope *S,
 
     // Fix a TSK_ImplicitInstantiation followed by a
     // TSK_ExplicitInstantiationDefinition
-    if (Old_TSK == TSK_ImplicitInstantiation &&
-        Specialization->hasAttr<DLLExportAttr>() &&
+    bool NewlyDLLExported =
+        !PreviouslyDLLExported && Specialization->hasAttr<DLLExportAttr>();
+    if (Old_TSK == TSK_ImplicitInstantiation && NewlyDLLExported &&
         (Context.getTargetInfo().getCXXABI().isMicrosoft() ||
          Context.getTargetInfo().getTriple().isWindowsItaniumEnvironment())) {
       // In the MS ABI, an explicit instantiation definition can add a dll
diff --git a/test/CodeGenCXX/dllexport.cpp b/test/CodeGenCXX/dllexport.cpp
index fe40bc0aac..33e524cc9b 100644
--- a/test/CodeGenCXX/dllexport.cpp
+++ b/test/CodeGenCXX/dllexport.cpp
@@ -732,13 +732,27 @@ USEMEMFUNC(ExplicitInstantiationDeclExportedDefTemplate<int>, f);
 // M32-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExplicitInstantiationDeclExportedDefTemplate* @"\01??0?$ExplicitInstantiationDeclExportedDefTemplate@H@@QAE@XZ"
 // G32-DAG: define weak_odr x86_thiscallcc void @_ZN44ExplicitInstantiationDeclExportedDefTemplateIiE1fEv
 
-template <typename T> struct ImplicitInstantiationExplicitInstantiationDefExportedTemplate { void f() {} };
+template <typename T> struct ImplicitInstantiationExportedExplicitInstantiationDefTemplate { virtual void f() {} };
+ImplicitInstantiationExportedExplicitInstantiationDefTemplate<int> ImplicitInstantiationExportedExplicitInstantiationDefTemplateInstance;
+template struct __declspec(dllexport) ImplicitInstantiationExportedExplicitInstantiationDefTemplate<int>;
+USEMEMFUNC(ImplicitInstantiationExportedExplicitInstantiationDefTemplate<int>, f);
+// M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?f@?$ImplicitInstantiationExportedExplicitInstantiationDefTemplate@H@@UAEXXZ"
+// G32-DAG: define weak_odr x86_thiscallcc void @_ZN61ImplicitInstantiationExportedExplicitInstantiationDefTemplateIiE1fEv
+
+template <typename T> struct __declspec(dllexport) ImplicitInstantiationExplicitInstantiationDefExportedTemplate { virtual void f() {} };
 ImplicitInstantiationExplicitInstantiationDefExportedTemplate<int> ImplicitInstantiationExplicitInstantiationDefExportedTemplateInstance;
-template class __declspec(dllexport) ImplicitInstantiationExplicitInstantiationDefExportedTemplate<int>;
+template struct ImplicitInstantiationExplicitInstantiationDefExportedTemplate<int>;
 USEMEMFUNC(ImplicitInstantiationExplicitInstantiationDefExportedTemplate<int>, f);
-// M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?f@?$ImplicitInstantiationExplicitInstantiationDefExportedTemplate@H@@QAEXXZ"
+// M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?f@?$ImplicitInstantiationExplicitInstantiationDefExportedTemplate@H@@UAEXXZ"
 // G32-DAG: define weak_odr x86_thiscallcc void @_ZN61ImplicitInstantiationExplicitInstantiationDefExportedTemplateIiE1fEv
 
+template <typename T> struct __declspec(dllexport) ImplicitInstantiationExportedExplicitInstantiationDefExportedTemplate { virtual void f() {} };
+ImplicitInstantiationExportedExplicitInstantiationDefExportedTemplate<int> ImplicitInstantiationExportedExplicitInstantiationDefExportedTemplateInstance;
+template struct __declspec(dllexport) ImplicitInstantiationExportedExplicitInstantiationDefExportedTemplate<int>;
+USEMEMFUNC(ImplicitInstantiationExportedExplicitInstantiationDefExportedTemplate<int>, f);
+// M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?f@?$ImplicitInstantiationExportedExplicitInstantiationDefExportedTemplate@H@@UAEXXZ"
+// G32-DAG: define weak_odr x86_thiscallcc void @_ZN69ImplicitInstantiationExportedExplicitInstantiationDefExportedTemplateIiE1fEv
+
 namespace { struct InternalLinkageType {}; }
 struct __declspec(dllexport) PR23308 {
   void f(InternalLinkageType*);
-- 
2.40.0