1 //===-- GenericBitset.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 "LibCxx.h"
10 #include "LibStdcpp.h"
11 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
12 #include "lldb/DataFormatters/FormattersHelpers.h"
13 #include "lldb/Target/Target.h"
14 
15 using namespace lldb;
16 using namespace lldb_private;
17 
18 namespace {
19 
20 /// This class can be used for handling bitsets from both libcxx and libstdcpp.
21 class GenericBitsetFrontEnd : public SyntheticChildrenFrontEnd {
22 public:
23   enum class StdLib {
24     LibCxx,
25     LibStdcpp,
26   };
27 
28   GenericBitsetFrontEnd(ValueObject &valobj, StdLib stdlib);
29 
30   size_t GetIndexOfChildWithName(ConstString name) override {
31     return formatters::ExtractIndexFromString(name.GetCString());
32   }
33 
34   bool MightHaveChildren() override { return true; }
35   bool Update() override;
36   size_t CalculateNumChildren() override { return m_elements.size(); }
37   ValueObjectSP GetChildAtIndex(size_t idx) override;
38 
39 private:
40   ConstString GetDataContainerMemberName();
41 
42   // The lifetime of a ValueObject and all its derivative ValueObjects
43   // (children, clones, etc.) is managed by a ClusterManager. These
44   // objects are only destroyed when every shared pointer to any of them
45   // is destroyed, so we must not store a shared pointer to any ValueObject
46   // derived from our backend ValueObject (since we're in the same cluster).
47   // Value objects created from raw data (i.e. in a different cluster) must
48   // be referenced via shared pointer to keep them alive, however.
49   std::vector<ValueObjectSP> m_elements;
50   ValueObject *m_first = nullptr;
51   CompilerType m_bool_type;
52   ByteOrder m_byte_order = eByteOrderInvalid;
53   uint8_t m_byte_size = 0;
54   StdLib m_stdlib;
55 };
56 } // namespace
57 
58 GenericBitsetFrontEnd::GenericBitsetFrontEnd(ValueObject &valobj, StdLib stdlib)
59     : SyntheticChildrenFrontEnd(valobj), m_stdlib(stdlib) {
60   m_bool_type = valobj.GetCompilerType().GetBasicTypeFromAST(eBasicTypeBool);
61   if (auto target_sp = m_backend.GetTargetSP()) {
62     m_byte_order = target_sp->GetArchitecture().GetByteOrder();
63     m_byte_size = target_sp->GetArchitecture().GetAddressByteSize();
64     Update();
65   }
66 }
67 
68 ConstString GenericBitsetFrontEnd::GetDataContainerMemberName() {
69   switch (m_stdlib) {
70   case StdLib::LibCxx:
71     return ConstString("__first_");
72   case StdLib::LibStdcpp:
73     return ConstString("_M_w");
74   }
75   llvm_unreachable("Unknown StdLib enum");
76 }
77 
78 bool GenericBitsetFrontEnd::Update() {
79   m_elements.clear();
80   m_first = nullptr;
81 
82   TargetSP target_sp = m_backend.GetTargetSP();
83   if (!target_sp)
84     return false;
85 
86   size_t size = 0;
87 
88   if (auto arg = m_backend.GetCompilerType().GetIntegralTemplateArgument(0))
89     size = arg->value.getLimitedValue();
90 
91   m_elements.assign(size, ValueObjectSP());
92   m_first = m_backend.GetChildMemberWithName(GetDataContainerMemberName(), true)
93                 .get();
94   return false;
95 }
96 
97 ValueObjectSP GenericBitsetFrontEnd::GetChildAtIndex(size_t idx) {
98   if (idx >= m_elements.size() || !m_first)
99     return ValueObjectSP();
100 
101   if (m_elements[idx])
102     return m_elements[idx];
103 
104   ExecutionContext ctx = m_backend.GetExecutionContextRef().Lock(false);
105   CompilerType type;
106   ValueObjectSP chunk;
107   // For small bitsets __first_ is not an array, but a plain size_t.
108   if (m_first->GetCompilerType().IsArrayType(&type)) {
109     llvm::Optional<uint64_t> bit_size =
110         type.GetBitSize(ctx.GetBestExecutionContextScope());
111     if (!bit_size || *bit_size == 0)
112       return {};
113     chunk = m_first->GetChildAtIndex(idx / *bit_size, true);
114   } else {
115     type = m_first->GetCompilerType();
116     chunk = m_first->GetSP();
117   }
118   if (!type || !chunk)
119     return {};
120 
121   llvm::Optional<uint64_t> bit_size =
122       type.GetBitSize(ctx.GetBestExecutionContextScope());
123   if (!bit_size || *bit_size == 0)
124     return {};
125   size_t chunk_idx = idx % *bit_size;
126   uint8_t value = !!(chunk->GetValueAsUnsigned(0) & (uint64_t(1) << chunk_idx));
127   DataExtractor data(&value, sizeof(value), m_byte_order, m_byte_size);
128 
129   m_elements[idx] = CreateValueObjectFromData(llvm::formatv("[{0}]", idx).str(),
130                                               data, ctx, m_bool_type);
131 
132   return m_elements[idx];
133 }
134 
135 SyntheticChildrenFrontEnd *formatters::LibStdcppBitsetSyntheticFrontEndCreator(
136     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
137   if (valobj_sp)
138     return new GenericBitsetFrontEnd(*valobj_sp,
139                                      GenericBitsetFrontEnd::StdLib::LibStdcpp);
140   return nullptr;
141 }
142 
143 SyntheticChildrenFrontEnd *formatters::LibcxxBitsetSyntheticFrontEndCreator(
144     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
145   if (valobj_sp)
146     return new GenericBitsetFrontEnd(*valobj_sp,
147                                      GenericBitsetFrontEnd::StdLib::LibCxx);
148   return nullptr;
149 }
150