Delay emitting dllexport explicitly defaulted members until the class is fully parsed (PR40006)

This is similar to r245139, but that only addressed dllexported classes.
It was still possible to run into the same problem with dllexported
members in an otherwise normal class (see bug). This uses the same
strategy to fix: delay defining the method until the whole class has
been parsed.

(The easiest way to see the ordering problem is in
Parser::ParseCXXMemberSpecification(): it calls
ParseLexedMemberInitializers() *after* ActOnFinishCXXMemberDecls(),
which was trying to define the dllexport method. Now we delay it to
ActOnFinishCXXNonNestedClass() which is called after both of those.)

Differential revision: https://reviews.llvm.org/D65511

llvm-svn: 367520

clang/include/clang/Sema/Sema.h

@@ -11136,6 +11136,7 @@ public:
   // Emitting members of dllexported classes is delayed until the class
   // (including field initializers) is fully parsed.
   SmallVector<CXXRecordDecl*, 4> DelayedDllExportClasses;
+  SmallVector<CXXMethodDecl*, 4> DelayedDllExportMemberFunctions;
 
 private:
   class SavePendingParsedClassStateRAII {

clang/lib/Sema/Sema.cpp

@@ -961,6 +961,7 @@ void Sema::ActOnEndOfTranslationUnit() {
 
   // All dllexport classes should have been processed already.
   assert(DelayedDllExportClasses.empty());
+  assert(DelayedDllExportMemberFunctions.empty());
 
   // Remove file scoped decls that turned out to be used.
   UnusedFileScopedDecls.erase(

clang/lib/Sema/SemaDeclCXX.cpp

@@ -6283,8 +6283,8 @@ void Sema::CheckCompletedCXXClass(CXXRecordDecl *Record) {
         M->dropAttr<DLLExportAttr>();
 
       if (M->hasAttr<DLLExportAttr>()) {
-        DefineImplicitSpecialMember(*this, M, M->getLocation());
-        ActOnFinishInlineFunctionDef(M);
+        // Define after any fields with in-class initializers have been parsed.
+        DelayedDllExportMemberFunctions.push_back(M);
       }
     }
   };
@@ -11537,6 +11537,15 @@ void Sema::ActOnFinishCXXMemberDecls() {
 
 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());
+      ActOnFinishInlineFunctionDef(M);
+    }
+  }
 }
 
 void Sema::referenceDLLExportedClassMethods() {

clang/test/CodeGenCXX/dllexport.cpp

@@ -851,6 +851,15 @@ struct __declspec(dllexport) Baz {
 // Baz's operator=, causing instantiation of Foo<int> after which
 // ActOnFinishCXXNonNestedClass is called, and we would bite our own tail.
 // M32-DAG: define weak_odr dso_local dllexport x86_thiscallcc dereferenceable(1) %"struct.InClassInits::Baz"* @"??4Baz@InClassInits@@QAEAAU01@ABU01@@Z"
+
+// 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"
+
 }
 
 // We had an issue where instantiating A would force emission of B's delayed