1 //===-- GenericOptional.cpp ----------------------------------------------===//
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 "Generic.h"
10 #include "LibCxx.h"
11 #include "LibStdcpp.h"
12 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
13 #include "lldb/DataFormatters/FormattersHelpers.h"
14 #include "lldb/Target/Target.h"
15 
16 using namespace lldb;
17 using namespace lldb_private;
18 
19 bool lldb_private::formatters::GenericOptionalSummaryProvider(
20     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
21   stream.Printf(" Has Value=%s ",
22                 valobj.GetNumChildren() == 0 ? "false" : "true");
23 
24   return true;
25 }
26 
27 // Synthetic Children Provider
28 namespace {
29 
30 class GenericOptionalFrontend : public SyntheticChildrenFrontEnd {
31 public:
32   enum class StdLib {
33     LibCxx,
34     LibStdcpp,
35   };
36 
37   GenericOptionalFrontend(ValueObject &valobj, StdLib stdlib);
38 
39   size_t GetIndexOfChildWithName(ConstString name) override {
40     return formatters::ExtractIndexFromString(name.GetCString());
41   }
42 
43   bool MightHaveChildren() override { return true; }
44   size_t CalculateNumChildren() override { return m_has_value ? 1U : 0U; }
45 
46   ValueObjectSP GetChildAtIndex(size_t idx) override;
47   bool Update() override;
48 
49 private:
50   bool m_has_value = false;
51   StdLib m_stdlib;
52 };
53 
54 } // namespace
55 
56 GenericOptionalFrontend::GenericOptionalFrontend(ValueObject &valobj,
57                                                  StdLib stdlib)
58     : SyntheticChildrenFrontEnd(valobj), m_stdlib(stdlib) {
59   if (auto target_sp = m_backend.GetTargetSP()) {
60     Update();
61   }
62 }
63 
64 bool GenericOptionalFrontend::Update() {
65   ValueObjectSP engaged_sp;
66 
67   if (m_stdlib == StdLib::LibCxx)
68     engaged_sp =
69         m_backend.GetChildMemberWithName(ConstString("__engaged_"), true);
70   else if (m_stdlib == StdLib::LibStdcpp)
71     engaged_sp =
72         m_backend.GetChildMemberWithName(ConstString("_M_payload"), true)
73             ->GetChildMemberWithName(ConstString("_M_engaged"), true);
74 
75   if (!engaged_sp)
76     return false;
77 
78   // _M_engaged/__engaged is a bool flag and is true if the optional contains a
79   // value. Converting it to unsigned gives us a size of 1 if it contains a
80   // value and 0 if not.
81   m_has_value = engaged_sp->GetValueAsUnsigned(0) != 0;
82 
83   return false;
84 }
85 
86 ValueObjectSP GenericOptionalFrontend::GetChildAtIndex(size_t _idx) {
87   if (!m_has_value)
88     return ValueObjectSP();
89 
90   ValueObjectSP val_sp;
91 
92   if (m_stdlib == StdLib::LibCxx)
93     // __val_ contains the underlying value of an optional if it has one.
94     // Currently because it is part of an anonymous union
95     // GetChildMemberWithName() does not peer through and find it unless we are
96     // at the parent itself. We can obtain the parent through __engaged_.
97     val_sp = m_backend.GetChildMemberWithName(ConstString("__engaged_"), true)
98                  ->GetParent()
99                  ->GetChildAtIndex(0, true)
100                  ->GetChildMemberWithName(ConstString("__val_"), true);
101   else if (m_stdlib == StdLib::LibStdcpp) {
102     val_sp = m_backend.GetChildMemberWithName(ConstString("_M_payload"), true)
103                  ->GetChildMemberWithName(ConstString("_M_payload"), true);
104 
105     // In some implementations, _M_value contains the underlying value of an
106     // optional, and in other versions, it's in the payload member.
107     ValueObjectSP candidate =
108         val_sp->GetChildMemberWithName(ConstString("_M_value"), true);
109     if (candidate)
110       val_sp = candidate;
111   }
112 
113   if (!val_sp)
114     return ValueObjectSP();
115 
116   CompilerType holder_type = val_sp->GetCompilerType();
117 
118   if (!holder_type)
119     return ValueObjectSP();
120 
121   return val_sp->Clone(ConstString("Value"));
122 }
123 
124 SyntheticChildrenFrontEnd *
125 formatters::LibStdcppOptionalSyntheticFrontEndCreator(
126     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
127   if (valobj_sp)
128     return new GenericOptionalFrontend(
129         *valobj_sp, GenericOptionalFrontend::StdLib::LibStdcpp);
130   return nullptr;
131 }
132 
133 SyntheticChildrenFrontEnd *formatters::LibcxxOptionalSyntheticFrontEndCreator(
134     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
135   if (valobj_sp)
136     return new GenericOptionalFrontend(*valobj_sp,
137                                        GenericOptionalFrontend::StdLib::LibCxx);
138   return nullptr;
139 }
140