From 2a58a18d67abe52eafc84b11b2ed6e9de491116f Mon Sep 17 00:00:00 2001
From: David Blaikie <dblaikie@gmail.com>
Date: Fri, 5 Aug 2016 19:03:01 +0000
Subject: [PATCH] PR26423: Assert on valid use of using declaration of a
 function with an undeduced auto return type

For now just disregard the using declaration in this case. Suboptimal,
but wiring up the ability to have declarations of functions that are
separate from their definition (we currently only do that for member
functions) and have differing return types (we don't have any support
for that) is more work than seems reasonable to at least fix this crash.

llvm-svn: 277852
---
 clang/lib/CodeGen/CGDebugInfo.cpp          | 10 ++++++++++
 clang/test/CodeGenCXX/debug-info-cxx1y.cpp | 26 ++++++++++++++++++++++----
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index d6cb798..8722e5a 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -3654,6 +3654,16 @@ void CGDebugInfo::EmitUsingDecl(const UsingDecl &UD) {
   // Emitting one decl is sufficient - debuggers can detect that this is an
   // overloaded name & provide lookup for all the overloads.
   const UsingShadowDecl &USD = **UD.shadow_begin();
+
+  // FIXME: Skip functions with undeduced auto return type for now since we
+  // don't currently have the plumbing for separate declarations & definitions
+  // of free functions and mismatched types (auto in the declaration, concrete
+  // return type in the definition)
+  if (const auto *FD = dyn_cast<FunctionDecl>(USD.getUnderlyingDecl()))
+    if (const auto *AT =
+            FD->getType()->getAs<FunctionProtoType>()->getContainedAutoType())
+      if (AT->getDeducedType().isNull())
+        return;
   if (llvm::DINode *Target =
           getDeclarationOrDefinition(USD.getUnderlyingDecl()))
     DBuilder.createImportedDeclaration(
diff --git a/clang/test/CodeGenCXX/debug-info-cxx1y.cpp b/clang/test/CodeGenCXX/debug-info-cxx1y.cpp
index faf29d3..36b3e09 100644
--- a/clang/test/CodeGenCXX/debug-info-cxx1y.cpp
+++ b/clang/test/CodeGenCXX/debug-info-cxx1y.cpp
@@ -1,16 +1,25 @@
 // RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm-only -std=c++14 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s
 
+// CHECK: imports: [[IMPS:![0-9]*]]
 // CHECK: [[EMPTY:![0-9]*]] = !{}
+
 // CHECK: [[FOO:![0-9]+]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "foo",
 // CHECK-SAME:             elements: [[EMPTY]]
-// FIXME: The context of this definition should be the CU/file scope, not the class.
-// CHECK: !DISubprogram(name: "func", {{.*}} scope: [[FOO]]
+
+// CHECK: [[IMPS]] = !{[[IMP:![0-9]*]]}
+// CHECK: [[IMP]] = !DIImportedEntity(
+// CHECK-SAME: entity: [[F3:![0-9]*]]
+// CHECK: [[F3]] = distinct !DISubprogram(name: "f3"
 // CHECK-SAME:          type: [[SUBROUTINE_TYPE:![0-9]*]]
-// CHECK-SAME:          isDefinition: true
-// CHECK-SAME:          declaration: [[FUNC_DECL:![0-9]*]]
 // CHECK: [[SUBROUTINE_TYPE]] = !DISubroutineType(types: [[TYPE_LIST:![0-9]*]])
 // CHECK: [[TYPE_LIST]] = !{[[INT:![0-9]*]]}
 // CHECK: [[INT]] = !DIBasicType(name: "int"
+
+// FIXME: The context of this definition should be the CU/file scope, not the class.
+// CHECK: !DISubprogram(name: "func", {{.*}} scope: [[FOO]]
+// CHECK-SAME:          type: [[SUBROUTINE_TYPE]]
+// CHECK-SAME:          isDefinition: true
+// CHECK-SAME:          declaration: [[FUNC_DECL:![0-9]*]]
 // CHECK: [[FUNC_DECL]] = !DISubprogram(name: "func",
 // CHECK-SAME:                          scope: [[FOO]]
 // CHECK-SAME:                          type: [[SUBROUTINE_TYPE]]
@@ -25,3 +34,12 @@ foo f;
 auto foo::func() {
   return 1;
 }
+
+namespace ns {
+auto f2();
+auto f3() {
+  return 0;
+}
+}
+using ns::f2;
+using ns::f3;
-- 
2.7.4