1 files changed, 85 insertions, 0 deletions
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp
new file mode 100644
index 00000000000..762b824f262
--- /dev/null
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxOptional.cpp
@@ -0,0 +1,85 @@
+//===-- LibCxxOptional.cpp --------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LibCxx.h"
+#include "lldb/DataFormatters/FormattersHelpers.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+namespace {
+
+class OptionalFrontEnd : public SyntheticChildrenFrontEnd {
+public:
+  OptionalFrontEnd(ValueObject &valobj) : SyntheticChildrenFrontEnd(valobj) {
+    Update();
+  }
+
+  size_t GetIndexOfChildWithName(const ConstString &name) override {
+    return formatters::ExtractIndexFromString(name.GetCString());
+  }
+
+  bool MightHaveChildren() override { return true; }
+  bool Update() override;
+  size_t CalculateNumChildren() override { return m_size; }
+  ValueObjectSP GetChildAtIndex(size_t idx) override;
+
+private:
+  size_t m_size = 0;
+  ValueObjectSP m_base_sp;
+};
+} // namespace
+
+bool OptionalFrontEnd::Update() {
+  ValueObjectSP engaged_sp(
+      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true));
+
+  if (!engaged_sp)
+    return false;
+
+  // __engaged_ is a bool flag and is true if the optional contains a value.
+  // Converting it to unsigned gives us a size of 1 if it contains a value
+  // and 0 if not.
+  m_size = engaged_sp->GetValueAsUnsigned(0);
+
+  return false;
+}
+
+ValueObjectSP OptionalFrontEnd::GetChildAtIndex(size_t idx) {
+  if (idx >= m_size)
+    return ValueObjectSP();
+
+  // __val_ contains the underlying value of an optional if it has one.
+  // Currently because it is part of an anonymous union GetChildMemberWithName()
+  // does not peer through and find it unless we are at the parent itself.
+  // We can obtain the parent through __engaged_.
+  ValueObjectSP val_sp(
+      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true)
+          ->GetParent()
+          ->GetChildAtIndex(0, true)
+          ->GetChildMemberWithName(ConstString("__val_"), true));
+
+  if (!val_sp)
+    return ValueObjectSP();
+
+  CompilerType holder_type = val_sp->GetCompilerType();
+
+  if (!holder_type)
+    return ValueObjectSP();
+
+  return val_sp->Clone(ConstString(llvm::formatv("Value").str()));
+}
+
+SyntheticChildrenFrontEnd *
+formatters::LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,
+                                          lldb::ValueObjectSP valobj_sp) {
+  if (valobj_sp)
+    return new OptionalFrontEnd(*valobj_sp);
+  return nullptr;
+}