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 
12 using namespace lldb;
13 using namespace lldb_private;
14 
15 namespace {
16 
17 class OptionalFrontEnd : public SyntheticChildrenFrontEnd {
18 public:
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 
32 private:
33   size_t m_size = 0;
34   ValueObjectSP m_base_sp;
35 };
36 } // namespace
37 
38 bool OptionalFrontEnd::Update() {
39   ValueObjectSP engaged_sp(
40       m_backend.GetChildMemberWithName(ConstString("__engaged_"), true));
41 
42   if (!engaged_sp)
43     return false;
44 
45   // __engaged_ is a bool flag and is true if the optional contains a value.
46   // Converting it to unsigned gives us a size of 1 if it contains a value
47   // and 0 if not.
48   m_size = engaged_sp->GetValueAsUnsigned(0);
49 
50   return false;
51 }
52 
53 ValueObjectSP OptionalFrontEnd::GetChildAtIndex(size_t idx) {
54   if (idx >= m_size)
55     return ValueObjectSP();
56 
57   // __val_ contains the underlying value of an optional if it has one.
58   // Currently because it is part of an anonymous union GetChildMemberWithName()
59   // does not peer through and find it unless we are at the parent itself.
60   // We can obtain the parent through __engaged_.
61   ValueObjectSP val_sp(
62       m_backend.GetChildMemberWithName(ConstString("__engaged_"), true)
63           ->GetParent()
64           ->GetChildAtIndex(0, true)
65           ->GetChildMemberWithName(ConstString("__val_"), true));
66 
67   if (!val_sp)
68     return ValueObjectSP();
69 
70   CompilerType holder_type = val_sp->GetCompilerType();
71 
72   if (!holder_type)
73     return ValueObjectSP();
74 
75   return val_sp->Clone(ConstString(llvm::formatv("Value").str()));
76 }
77 
78 SyntheticChildrenFrontEnd *
79 formatters::LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,
80                                           lldb::ValueObjectSP valobj_sp) {
81   if (valobj_sp)
82     return new OptionalFrontEnd(*valobj_sp);
83   return nullptr;
84 }
85