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LibCxxSpan.cpp
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1//===-- LibCxxSpan.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
14#include "llvm/ADT/APSInt.h"
15#include <optional>
16
17using namespace lldb;
18using namespace lldb_private;
19using namespace lldb_private::formatters;
20
21namespace lldb_private {
22namespace formatters {
23
25public:
26 LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp);
27
28 ~LibcxxStdSpanSyntheticFrontEnd() override = default;
29
30 size_t CalculateNumChildren() override;
31
32 lldb::ValueObjectSP GetChildAtIndex(size_t idx) override;
33
34 /// Determines properties of the std::span<> associated with this object
35 //
36 // std::span can either be instantiated with a compile-time known
37 // extent or a std::dynamic_extent (this is the default if only the
38 // type template argument is provided). The layout of std::span
39 // depends on whether the extent is dynamic or not. For static
40 // extents (e.g., std::span<int, 9>):
41 //
42 // (std::__1::span<const int, 9>) s = {
43 // __data = 0x000000016fdff494
44 // }
45 //
46 // For dynamic extents, e.g., std::span<int>, the layout is:
47 //
48 // (std::__1::span<const int, 18446744073709551615>) s = {
49 // __data = 0x000000016fdff494
50 // __size = 6
51 // }
52 //
53 // This function checks for a '__size' member to determine the number
54 // of elements in the span. If no such member exists, we get the size
55 // from the only other place it can be: the template argument.
56 bool Update() override;
57
58 bool MightHaveChildren() override;
59
60 size_t GetIndexOfChildWithName(ConstString name) override;
61
62private:
63 ValueObject *m_start = nullptr; ///< First element of span. Held, not owned.
64 CompilerType m_element_type{}; ///< Type of span elements.
65 size_t m_num_elements = 0; ///< Number of elements in span.
66 uint32_t m_element_size = 0; ///< Size in bytes of each span element.
67};
68
70 LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
71 : SyntheticChildrenFrontEnd(*valobj_sp) {
72 if (valobj_sp)
73 Update();
74}
75
78 return m_num_elements;
79}
80
81lldb::ValueObjectSP
83 size_t idx) {
84 if (!m_start)
85 return {};
86
87 uint64_t offset = idx * m_element_size;
88 offset = offset + m_start->GetValueAsUnsigned(0);
89 StreamString name;
90 name.Printf("[%" PRIu64 "]", (uint64_t)idx);
91 return CreateValueObjectFromAddress(name.GetString(), offset,
92 m_backend.GetExecutionContextRef(),
93 m_element_type);
94}
95
97 // Get element type.
98 ValueObjectSP data_type_finder_sp = GetChildMemberWithName(
99 m_backend, {ConstString("__data_"), ConstString("__data")});
100 if (!data_type_finder_sp)
101 return false;
102
103 m_element_type = data_type_finder_sp->GetCompilerType().GetPointeeType();
104
105 // Get element size.
106 if (std::optional<uint64_t> size = m_element_type.GetByteSize(nullptr)) {
107 m_element_size = *size;
108
109 // Get data.
110 if (m_element_size > 0) {
111 m_start = data_type_finder_sp.get();
112 }
113
114 // Get number of elements.
115 if (auto size_sp = GetChildMemberWithName(
116 m_backend, {ConstString("__size_"), ConstString("__size")})) {
117 m_num_elements = size_sp->GetValueAsUnsigned(0);
118 } else if (auto arg =
119 m_backend.GetCompilerType().GetIntegralTemplateArgument(1)) {
120
121 m_num_elements = arg->value.getLimitedValue();
122 }
123 }
124
125 return true;
126}
127
130 return true;
131}
132
135 if (!m_start)
136 return UINT32_MAX;
137 return ExtractIndexFromString(name.GetCString());
138}
139
142 lldb::ValueObjectSP valobj_sp) {
143 if (!valobj_sp)
144 return nullptr;
145 CompilerType type = valobj_sp->GetCompilerType();
146 if (!type.IsValid() || type.GetNumTemplateArguments() != 2)
147 return nullptr;
148 return new LibcxxStdSpanSyntheticFrontEnd(valobj_sp);
149}
150
151} // namespace formatters
152} // namespace lldb_private
Generic representation of a type in a programming language.
Definition: CompilerType.h:36
size_t GetNumTemplateArguments(bool expand_pack=false) const
Return the number of template arguments the type has.
A uniqued constant string class.
Definition: ConstString.h:40
const char * GetCString() const
Get the string value as a C string.
Definition: ConstString.h:221
llvm::StringRef GetString() const
size_t Printf(const char *format,...) __attribute__((format(printf
Output printf formatted output to the stream.
Definition: Stream.cpp:107
LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
Definition: LibCxxSpan.cpp:70
CompilerType m_element_type
Type of span elements.
Definition: LibCxxSpan.cpp:64
ValueObject * m_start
First element of span. Held, not owned.
Definition: LibCxxSpan.cpp:63
bool Update() override
Determines properties of the std::span<> associated with this object.
Definition: LibCxxSpan.cpp:96
lldb::ValueObjectSP GetChildAtIndex(size_t idx) override
Definition: LibCxxSpan.cpp:82
size_t m_num_elements
Number of elements in span.
Definition: LibCxxSpan.cpp:65
uint32_t m_element_size
Size in bytes of each span element.
Definition: LibCxxSpan.cpp:66
size_t GetIndexOfChildWithName(ConstString name) override
Definition: LibCxxSpan.cpp:134
#define UINT32_MAX
Definition: lldb-defines.h:19
SyntheticChildrenFrontEnd * LibcxxStdSpanSyntheticFrontEndCreator(CXXSyntheticChildren *, lldb::ValueObjectSP)
Definition: LibCxxSpan.cpp:141
lldb::ValueObjectSP GetChildMemberWithName(ValueObject &obj, llvm::ArrayRef< ConstString > alternative_names)
Find a child member of obj_sp, trying all alternative names in order.
Definition: LibCxx.cpp:38
size_t ExtractIndexFromString(const char *item_name)
A class that represents a running process on the host machine.
Definition: SBAttachInfo.h:14
Definition: SBAddress.h:15