Don't try emitting dllexported explicitly defaulted non-trivial ctors twice during explicit template instantiation definition (PR42857)

[hans]

Summary

Trying to emit the definition twice triggers an assert.

[rnk]

lgtm

yeesh.

cfe/trunk/lib/Sema/SemaDeclCXX.cpp

 void Sema::ActOnFinishCXXNonNestedClass(Decl *D) {
   referenceDLLExportedClassMethods();
 
   if (!DelayedDllExportMemberFunctions.empty()) {
     SmallVector<CXXMethodDecl*, 4> WorkList;
     std::swap(DelayedDllExportMemberFunctions, WorkList);
     for (CXXMethodDecl *M : WorkList) {
       DefineImplicitSpecialMember(*this, M, M->getLocation());
+
+      // Pass the method to the consumer to get emitted. This is not necessary
+      // for explicit instantiation definitions, as they will get emitted
+      // anyway.
+      if (M->getParent()->getTemplateSpecializationKind() !=
+          TSK_ExplicitInstantiationDefinition)
         ActOnFinishInlineFunctionDef(M);
     }
   }
 }
 
 void Sema::referenceDLLExportedClassMethods() {
   if (!DelayedDllExportClasses.empty()) {
     // Calling ReferenceDllExportedMembers might cause the current function to
     // be called again, so use a local copy of DelayedDllExportClasses.

cfe/trunk/test/CodeGenCXX/dllexport.cpp

 // Trying to define the explicitly defaulted ctor must be delayed until the
 // in-class initializer for x has been processed.
 struct PR40006 {
   __declspec(dllexport) PR40006() = default;
   int x = 42;
 };
 // M32-DAG: define weak_odr dso_local dllexport x86_thiscallcc %"struct.InClassInits::PR40006"* @"??0PR40006@InClassInits@@QAE@XZ"
 
+// PR42857: Clang would try to emit the non-trivial explicitly defaulted
+// dllexport ctor twice when doing an explicit instantiation definition.
+struct Qux { Qux(); };
+template <typename T> struct PR42857 { __declspec(dllexport) PR42857() = default; Qux q; };
+template struct PR42857<int>;
+// M32-DAG: define weak_odr dso_local dllexport x86_thiscallcc %"struct.InClassInits::PR42857"* @"??0?$PR42857@H@InClassInits@@QAE@XZ"
+
 }
 
 // We had an issue where instantiating A would force emission of B's delayed
 // exported methods.
 namespace pr26490 {
 template <typename T> struct A { };
 struct __declspec(dllexport) B {
   B(int = 0) {}