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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:
27
28 ~LibcxxStdSpanSyntheticFrontEnd() override = default;
29
30 llvm::Expected<uint32_t> CalculateNumChildren() override;
31
32 lldb::ValueObjectSP GetChildAtIndex(uint32_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.
57
58 llvm::Expected<size_t> GetIndexOfChildWithName(ConstString name) override;
59
60private:
61 ValueObject *m_start = nullptr; ///< First element of span. Held, not owned.
62 CompilerType m_element_type{}; ///< Type of span elements.
63 size_t m_num_elements = 0; ///< Number of elements in span.
64 uint32_t m_element_size = 0; ///< Size in bytes of each span element.
65};
66
73
78
81 uint32_t idx) {
82 if (!m_start)
83 return {};
84
85 uint64_t offset = idx * m_element_size;
86 offset = offset + m_start->GetValueAsUnsigned(0);
87 StreamString name;
88 name.Printf("[%" PRIu64 "]", (uint64_t)idx);
89 return CreateValueObjectFromAddress(name.GetString(), offset,
90 m_backend.GetExecutionContextRef(),
92}
93
96 // Get element type.
97 ValueObjectSP data_type_finder_sp = GetChildMemberWithName(
98 m_backend, {ConstString("__data_"), ConstString("__data")});
99 if (!data_type_finder_sp)
101
102 m_element_type = data_type_finder_sp->GetCompilerType().GetPointeeType();
103
104 // Get element size.
105 llvm::Expected<uint64_t> size_or_err = m_element_type.GetByteSize(nullptr);
106 if (!size_or_err)
107 LLDB_LOG_ERRORV(GetLog(LLDBLog::DataFormatters), size_or_err.takeError(),
108 "{0}");
109 else {
110 m_element_size = *size_or_err;
111
112 // Get data.
113 if (m_element_size > 0) {
114 m_start = data_type_finder_sp.get();
115 }
116
117 // Get number of elements.
118 if (auto size_sp = GetChildMemberWithName(
119 m_backend, {ConstString("__size_"), ConstString("__size")})) {
120 m_num_elements = size_sp->GetValueAsUnsigned(0);
121 } else if (auto arg =
122 m_backend.GetCompilerType().GetIntegralTemplateArgument(1)) {
123
124 m_num_elements = arg->value.GetAPSInt().getLimitedValue();
125 }
126 }
127
129}
130
131llvm::Expected<size_t> lldb_private::formatters::
133 if (!m_start)
134 return llvm::createStringError("Type has no child named '%s'",
135 name.AsCString());
136 auto optional_idx = formatters::ExtractIndexFromString(name.GetCString());
137 if (!optional_idx) {
138 return llvm::createStringError("Type has no child named '%s'",
139 name.AsCString());
140 }
141 return *optional_idx;
142}
143
146 lldb::ValueObjectSP valobj_sp) {
147 if (!valobj_sp)
148 return nullptr;
149 CompilerType type = valobj_sp->GetCompilerType();
150 if (!type.IsValid() || type.GetNumTemplateArguments() != 2)
151 return nullptr;
152 return new LibcxxStdSpanSyntheticFrontEnd(valobj_sp);
153}
154
155} // namespace formatters
156} // namespace lldb_private
#define LLDB_LOG_ERRORV(log, error,...)
Definition Log.h:408
Generic representation of a type in a programming language.
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 * AsCString(const char *value_if_empty=nullptr) const
Get the string value as a C string.
const char * GetCString() const
Get the string value as a C string.
llvm::StringRef GetString() const
size_t Printf(const char *format,...) __attribute__((format(printf
Output printf formatted output to the stream.
Definition Stream.cpp:134
SyntheticChildrenFrontEnd(ValueObject &backend)
lldb::ValueObjectSP CreateValueObjectFromAddress(llvm::StringRef name, uint64_t address, const ExecutionContext &exe_ctx, CompilerType type, bool do_deref=true)
LibcxxStdSpanSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
CompilerType m_element_type
Type of span elements.
llvm::Expected< size_t > GetIndexOfChildWithName(ConstString name) override
lldb::ChildCacheState Update() override
Determines properties of the std::span<> associated with this object.
lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override
ValueObject * m_start
First element of span. Held, not owned.
llvm::Expected< uint32_t > CalculateNumChildren() override
uint32_t m_element_size
Size in bytes of each span element.
SyntheticChildrenFrontEnd * LibcxxStdSpanSyntheticFrontEndCreator(CXXSyntheticChildren *, lldb::ValueObjectSP)
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:63
std::optional< size_t > ExtractIndexFromString(const char *item_name)
A class that represents a running process on the host machine.
Log * GetLog(Cat mask)
Retrieve the Log object for the channel associated with the given log enum.
Definition Log.h:332
ChildCacheState
Specifies if children need to be re-computed after a call to SyntheticChildrenFrontEnd::Update.
@ eRefetch
Children need to be recomputed dynamically.
@ eReuse
Children did not change and don't need to be recomputed; re-use what we computed the last time we cal...
std::shared_ptr< lldb_private::ValueObject > ValueObjectSP