From 4a38c1f9dd8045503a8c6bb7855232a5eba4566b Mon Sep 17 00:00:00 2001
From: Nico Weber <nicolasweber@gmx.de>
Date: Fri, 15 Aug 2014 23:21:41 +0000
Subject: [PATCH] Make sure that vtables referenced from delay-parsed templates
 get referenced.

This fixes PR20671, see the bug for details. In short, ActOnTranslationUnit()
calls DefineUsedVTables() and only then PerformPendingInstantiations(). But
PerformPendingInstantiations() is what does delayed template parsing, so
vtables only references from late-parsed templates weren't marked used.

As a fix, move the SavePendingInstantiationsAndVTableUsesRAII in
PerformPendingInstantiations() up above the delayed template parsing code.
That way, vtables referenced from templates end up in the RAII object, and the
call to DefineUsedVTables() in PerformPendingInstantiations() marks them used.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215786 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaTemplateInstantiateDecl.cpp      | 27 ++++++++++---------
 ...crosoft-abi-structors-delayed-template.cpp | 12 +++++++++
 2 files changed, 27 insertions(+), 12 deletions(-)
 create mode 100644 test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp

diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index b73c2b137c..747eaf6d96 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3319,6 +3319,20 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
     return;
   }
 
+  // If we're performing recursive template instantiation, create our own
+  // queue of pending implicit instantiations that we will instantiate later,
+  // while we're still within our own instantiation context.
+  // This has to happen before LateTemplateParser below is called, so that
+  // it marks vtables used in late parsed templates as used.
+  SavePendingLocalImplicitInstantiationsRAII
+      SavedPendingLocalImplicitInstantiations(*this);
+  std::unique_ptr<SavePendingInstantiationsAndVTableUsesRAII>
+      SavePendingInstantiationsAndVTableUses;
+  if (Recursive) {
+    SavePendingInstantiationsAndVTableUses.reset(
+        new SavePendingInstantiationsAndVTableUsesRAII(*this));
+  }
+
   // Call the LateTemplateParser callback if there is a need to late parse
   // a templated function definition.
   if (!Pattern && PatternDecl->isLateTemplateParsed() &&
@@ -3350,6 +3364,7 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
       Function->setInvalidDecl();
     } else if (Function->getTemplateSpecializationKind()
                  == TSK_ExplicitInstantiationDefinition) {
+      assert(!Recursive);
       PendingInstantiations.push_back(
         std::make_pair(Function, PointOfInstantiation));
     }
@@ -3386,18 +3401,6 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
   // Copy the inner loc start from the pattern.
   Function->setInnerLocStart(PatternDecl->getInnerLocStart());
 
-  // If we're performing recursive template instantiation, create our own
-  // queue of pending implicit instantiations that we will instantiate later,
-  // while we're still within our own instantiation context.
-  SavePendingLocalImplicitInstantiationsRAII
-      SavedPendingLocalImplicitInstantiations(*this);
-  std::unique_ptr<SavePendingInstantiationsAndVTableUsesRAII>
-      SavePendingInstantiationsAndVTableUses;
-  if (Recursive) {
-    SavePendingInstantiationsAndVTableUses.reset(
-        new SavePendingInstantiationsAndVTableUsesRAII(*this));
-  }
-
   EnterExpressionEvaluationContext EvalContext(*this,
                                                Sema::PotentiallyEvaluated);
 
diff --git a/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp b/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp
new file mode 100644
index 0000000000..f9e188033c
--- /dev/null
+++ b/test/CodeGenCXX/microsoft-abi-structors-delayed-template.cpp
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -emit-llvm -fdelayed-template-parsing -std=c++11 -o - -triple=i386-pc-win32 %s > %t
+// RUN: FileCheck %s < %t
+
+// PR20671
+namespace vtable_referenced_from_template {
+struct ImplicitCtor {
+  virtual ~ImplicitCtor();
+};
+template <class T> void foo(T t) { new ImplicitCtor; }
+void bar() { foo(0); }
+// CHECK: store {{.*}} @"\01??_7ImplicitCtor@vtable_referenced_from_template@@6B@"
+}
-- 
2.40.0