1 //===-- LibCxxOptional.cpp --------------------------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "LibCxx.h"
11 #include "lldb/DataFormatters/FormattersHelpers.h"
12 
13 using namespace lldb;
14 using namespace lldb_private;
15 
16 namespace {
17 
18 class OptionalFrontEnd : public SyntheticChildrenFrontEnd {
19 public:
OptionalFrontEnd(ValueObject & valobj)20   OptionalFrontEnd(ValueObject &valobj) : SyntheticChildrenFrontEnd(valobj) {
21     Update();
22   }
23 
GetIndexOfChildWithName(const ConstString & name)24   size_t GetIndexOfChildWithName(const ConstString &name) override {
25     return formatters::ExtractIndexFromString(name.GetCString());
26   }
27 
MightHaveChildren()28   bool MightHaveChildren() override { return true; }
29   bool Update() override;
CalculateNumChildren()30   size_t CalculateNumChildren() override { return m_size; }
31   ValueObjectSP GetChildAtIndex(size_t idx) override;
32 
33 private:
34   size_t m_size = 0;
35   ValueObjectSP m_base_sp;
36 };
37 } // namespace
38 
Update()39 bool OptionalFrontEnd::Update() {
40   ValueObjectSP engaged_sp(
41       m_backend.GetChildMemberWithName(ConstString("__engaged_"), true));
42 
43   if (!engaged_sp)
44     return false;
45 
46   // __engaged_ is a bool flag and is true if the optional contains a value.
47   // Converting it to unsigned gives us a size of 1 if it contains a value
48   // and 0 if not.
49   m_size = engaged_sp->GetValueAsUnsigned(0);
50 
51   return false;
52 }
53 
GetChildAtIndex(size_t idx)54 ValueObjectSP OptionalFrontEnd::GetChildAtIndex(size_t idx) {
55   if (idx >= m_size)
56     return ValueObjectSP();
57 
58   // __val_ contains the underlying value of an optional if it has one.
59   // Currently because it is part of an anonymous union GetChildMemberWithName()
60   // does not peer through and find it unless we are at the parent itself.
61   // We can obtain the parent through __engaged_.
62   ValueObjectSP val_sp(
63       m_backend.GetChildMemberWithName(ConstString("__engaged_"), true)
64           ->GetParent()
65           ->GetChildAtIndex(0, true)
66           ->GetChildMemberWithName(ConstString("__val_"), true));
67 
68   if (!val_sp)
69     return ValueObjectSP();
70 
71   CompilerType holder_type = val_sp->GetCompilerType();
72 
73   if (!holder_type)
74     return ValueObjectSP();
75 
76   return val_sp->Clone(ConstString(llvm::formatv("Value").str()));
77 }
78 
79 SyntheticChildrenFrontEnd *
LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,lldb::ValueObjectSP valobj_sp)80 formatters::LibcxxOptionalFrontEndCreator(CXXSyntheticChildren *,
81                                           lldb::ValueObjectSP valobj_sp) {
82   if (valobj_sp)
83     return new OptionalFrontEnd(*valobj_sp);
84   return nullptr;
85 }
86