LibCxxOptional.cpp revision 360784 
1//===-- LibCxxOptional.cpp --------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "LibCxx.h"
10#include "lldb/DataFormatters/FormattersHelpers.h"
11
12using namespace lldb;
13using namespace lldb_private;
14
15namespace {
16
17class OptionalFrontEnd : public SyntheticChildrenFrontEnd {
18public:
19  OptionalFrontEnd(ValueObject &valobj) : SyntheticChildrenFrontEnd(valobj) {
20    Update();
21  }
22
23  size_t GetIndexOfChildWithName(ConstString name) override {
24    return formatters::ExtractIndexFromString(name.GetCString());
25  }
26
27  bool MightHaveChildren() override { return true; }
28  bool Update() override;
29  size_t CalculateNumChildren() override { return m_size; }
30  ValueObjectSP GetChildAtIndex(size_t idx) override;
31
32private:
33  size_t m_size = 0;
34};
35} // namespace
36
37bool OptionalFrontEnd::Update() {
38  ValueObjectSP engaged_sp(
39      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true));
40
41  if (!engaged_sp)
42    return false;
43
44  // __engaged_ is a bool flag and is true if the optional contains a value.
45  // Converting it to unsigned gives us a size of 1 if it contains a value
46  // and 0 if not.
47  m_size = engaged_sp->GetValueAsUnsigned(0);
48
49  return false;
50}
51
52ValueObjectSP OptionalFrontEnd::GetChildAtIndex(size_t idx) {
53  if (idx >= m_size)
54    return ValueObjectSP();
55
56  // __val_ contains the underlying value of an optional if it has one.
57  // Currently because it is part of an anonymous union GetChildMemberWithName()
58  // does not peer through and find it unless we are at the parent itself.
59  // We can obtain the parent through __engaged_.
60  ValueObjectSP val_sp(
61      m_backend.GetChildMemberWithName(ConstString("__engaged_"), true)
62          ->GetParent()
63          ->GetChildAtIndex(0, true)
64          ->GetChildMemberWithName(ConstString("__val_"), true));
65
66  if (!val_sp)
67    return ValueObjectSP();
68
69  CompilerType holder_type = val_sp->GetCompilerType();
70
71  if (!holder_type)
72    return ValueObjectSP();
73
74  return val_sp->Clone(ConstString(llvm::formatv("Value").str()));
75}
76
77SyntheticChildrenFrontEnd *
78formatters::LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,
79                                          lldb::ValueObjectSP valobj_sp) {
80  if (valobj_sp)
81    return new OptionalFrontEnd(*valobj_sp);
82  return nullptr;
83}
84