Fix a crash when emitting dbeug info for forward-declared scoped enums.

It is possible for enums to be created as part of their own
declcontext. We need to cache a placeholder to avoid the type being
created twice before hitting the cache.

<rdar://problem/24493203>

llvm-svn: 259975

2 files changed, 28 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 7bd0e11439f..34dcea11266 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2051,13 +2051,25 @@ llvm::DIType *CGDebugInfo::CreateEnumType(const EnumType *Ty) {
   // If this is just a forward declaration, construct an appropriately
   // marked node and just return it.
   if (isImportedFromModule || !ED->getDefinition()) {
-    llvm::DIScope *EDContext = getDeclContextDescriptor(ED);
     llvm::DIFile *DefUnit = getOrCreateFile(ED->getLocation());
+
+    // It is possible for enums to be created as part of their own
+    // declcontext. We need to cache a placeholder to avoid the type being
+    // created twice before hitting the cache.
+    llvm::DIScope *EDContext = DBuilder.createReplaceableCompositeType(
+      llvm::dwarf::DW_TAG_enumeration_type, "", TheCU, DefUnit, 0);
+
     unsigned Line = getLineNumber(ED->getLocation());
     StringRef EDName = ED->getName();
     llvm::DIType *RetTy = DBuilder.createReplaceableCompositeType(
         llvm::dwarf::DW_TAG_enumeration_type, EDName, EDContext, DefUnit, Line,
         0, Size, Align, llvm::DINode::FlagFwdDecl, FullName);
+
+    // Cache the enum type so it is available when building the declcontext
+    // and replace the declcontect with the real thing.
+    TypeCache[Ty].reset(RetTy);
+    EDContext->replaceAllUsesWith(getDeclContextDescriptor(ED));
+
     ReplaceMap.emplace_back(
         std::piecewise_construct, std::make_tuple(Ty),
         std::make_tuple(static_cast<llvm::Metadata *>(RetTy)));
diff --git a/clang/test/CodeGenCXX/debug-info-scoped-class.cpp b/clang/test/CodeGenCXX/debug-info-scoped-class.cpp
new file mode 100644
index 00000000000..de4aee9a1b4
--- /dev/null
+++ b/clang/test/CodeGenCXX/debug-info-scoped-class.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -emit-llvm -debug-info-kind=standalone -std=c++11 \
+// RUN:   -triple thumbv7-apple-ios %s -o - | FileCheck %s
+
+// This forward-declared scoped enum will be created while building its own
+// declcontext. Make sure it is only emitted once.
+
+struct A {
+  enum class Return;
+  Return f1();
+};
+A::Return* f2() {}
+
+// CHECK: !DICompositeType(tag: DW_TAG_enumeration_type, name: "Return",
+// CHECK-SAME:             flags: DIFlagFwdDecl,
+// CHECK-NOT:              tag: DW_TAG_enumeration_type, name: "Return"