1//===-- ValueObjectVariable.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 "lldb/ValueObject/ValueObjectVariable.h"
10
11#include "lldb/Core/Address.h"
12#include "lldb/Core/AddressRange.h"
13#include "lldb/Core/Declaration.h"
14#include "lldb/Core/Module.h"
15#include "lldb/Core/Value.h"
16#include "lldb/Expression/DWARFExpressionList.h"
17#include "lldb/Symbol/Function.h"
18#include "lldb/Symbol/ObjectFile.h"
19#include "lldb/Symbol/SymbolContext.h"
20#include "lldb/Symbol/SymbolContextScope.h"
21#include "lldb/Symbol/Type.h"
22#include "lldb/Symbol/Variable.h"
23#include "lldb/Target/ExecutionContext.h"
24#include "lldb/Target/Process.h"
25#include "lldb/Target/RegisterContext.h"
26#include "lldb/Target/Target.h"
27#include "lldb/Utility/DataExtractor.h"
28#include "lldb/Utility/RegisterValue.h"
29#include "lldb/Utility/Scalar.h"
30#include "lldb/Utility/Status.h"
31#include "lldb/lldb-private-enumerations.h"
32#include "lldb/lldb-types.h"
33
34#include "llvm/ADT/StringRef.h"
35
36#include <cassert>
37#include <memory>
38#include <optional>
39
40namespace lldb_private {
41class ExecutionContextScope;
42}
43namespace lldb_private {
44class StackFrame;
45}
46namespace lldb_private {
47struct RegisterInfo;
48}
49using namespace lldb_private;
50
51lldb::ValueObjectSP
52ValueObjectVariable::Create(ExecutionContextScope *exe_scope,
53 const lldb::VariableSP &var_sp) {
54 auto manager_sp = ValueObjectManager::Create();
55 return (new ValueObjectVariable(exe_scope, *manager_sp, var_sp))->GetSP();
56}
57
58ValueObjectVariable::ValueObjectVariable(ExecutionContextScope *exe_scope,
59 ValueObjectManager &manager,
60 const lldb::VariableSP &var_sp)
61 : ValueObject(exe_scope, manager), m_variable_sp(var_sp) {
62 // Do not attempt to construct one of these objects with no variable!
63 assert(m_variable_sp.get() != nullptr);
64 m_name = var_sp->GetName();
65}
66
67ValueObjectVariable::~ValueObjectVariable() = default;
68
69CompilerType ValueObjectVariable::GetCompilerTypeImpl() {
70 Type *var_type = m_variable_sp->GetType();
71 if (var_type)
72 return var_type->GetForwardCompilerType();
73 return CompilerType();
74}
75
76ConstString ValueObjectVariable::GetTypeName() {
77 Type *var_type = m_variable_sp->GetType();
78 if (var_type)
79 return var_type->GetName();
80 return ConstString();
81}
82
83ConstString ValueObjectVariable::GetDisplayTypeName() {
84 Type *var_type = m_variable_sp->GetType();
85 if (var_type)
86 return var_type->GetForwardCompilerType().GetDisplayTypeName();
87 return ConstString();
88}
89
90ConstString ValueObjectVariable::GetQualifiedTypeName() {
91 Type *var_type = m_variable_sp->GetType();
92 if (var_type)
93 return var_type->GetQualifiedName();
94 return ConstString();
95}
96
97llvm::Expected<uint32_t>
98ValueObjectVariable::CalculateNumChildren(uint32_t max) {
99 CompilerType type(GetCompilerType());
100
101 if (!type.IsValid())
102 return llvm::make_error<llvm::StringError>(Args: "invalid type",
103 Args: llvm::inconvertibleErrorCode());
104
105 ExecutionContext exe_ctx(GetExecutionContextRef());
106 const bool omit_empty_base_classes = true;
107 auto child_count = type.GetNumChildren(omit_empty_base_classes, exe_ctx: &exe_ctx);
108 if (!child_count)
109 return child_count;
110 return *child_count <= max ? *child_count : max;
111}
112
113llvm::Expected<uint64_t> ValueObjectVariable::GetByteSize() {
114 ExecutionContext exe_ctx(GetExecutionContextRef());
115
116 CompilerType type(GetCompilerType());
117 return type.GetByteSize(exe_scope: exe_ctx.GetBestExecutionContextScope());
118}
119
120lldb::ValueType ValueObjectVariable::GetValueType() const {
121 if (m_variable_sp)
122 return m_variable_sp->GetScope();
123 return lldb::eValueTypeInvalid;
124}
125
126bool ValueObjectVariable::UpdateValue() {
127 SetValueIsValid(false);
128 m_error.Clear();
129
130 Variable *variable = m_variable_sp.get();
131 DWARFExpressionList &expr_list = variable->LocationExpressionList();
132
133 if (variable->GetLocationIsConstantValueData()) {
134 // expr doesn't contain DWARF bytes, it contains the constant variable
135 // value bytes themselves...
136 if (expr_list.GetExpressionData(data&: m_data)) {
137 if (m_data.GetDataStart() && m_data.GetByteSize())
138 m_value.SetBytes(bytes: m_data.GetDataStart(), len: m_data.GetByteSize());
139 m_value.SetContext(context_type: Value::ContextType::Variable, p: variable);
140 } else
141 m_error = Status::FromErrorString(str: "empty constant data");
142 // constant bytes can't be edited - sorry
143 m_resolved_value.SetContext(context_type: Value::ContextType::Invalid, p: nullptr);
144 } else {
145 lldb::addr_t loclist_base_load_addr = LLDB_INVALID_ADDRESS;
146 ExecutionContext exe_ctx(GetExecutionContextRef());
147
148 Target *target = exe_ctx.GetTargetPtr();
149 if (target) {
150 m_data.SetByteOrder(target->GetArchitecture().GetByteOrder());
151 m_data.SetAddressByteSize(target->GetArchitecture().GetAddressByteSize());
152 }
153
154 if (!expr_list.IsAlwaysValidSingleExpr()) {
155 SymbolContext sc;
156 variable->CalculateSymbolContext(sc: &sc);
157 if (sc.function)
158 loclist_base_load_addr =
159 sc.function->GetAddress().GetLoadAddress(target);
160 }
161 Value old_value(m_value);
162 llvm::Expected<Value> maybe_value = expr_list.Evaluate(
163 exe_ctx: &exe_ctx, reg_ctx: nullptr, func_load_addr: loclist_base_load_addr, initial_value_ptr: nullptr, object_address_ptr: nullptr);
164
165 if (maybe_value) {
166 m_value = *maybe_value;
167 m_resolved_value = m_value;
168 m_value.SetContext(context_type: Value::ContextType::Variable, p: variable);
169
170 CompilerType compiler_type = GetCompilerType();
171 if (compiler_type.IsValid())
172 m_value.SetCompilerType(compiler_type);
173
174 Value::ValueType value_type = m_value.GetValueType();
175
176 // The size of the buffer within m_value can be less than the size
177 // prescribed by its type. E.g. this can happen when an expression only
178 // partially describes an object (say, because it contains DW_OP_piece).
179 //
180 // In this case, grow m_value to the expected size. An alternative way to
181 // handle this is to teach Value::GetValueAsData() and ValueObjectChild
182 // not to read past the end of a host buffer, but this gets impractically
183 // complicated as a Value's host buffer may be shared with a distant
184 // ancestor or sibling in the ValueObject hierarchy.
185 //
186 // FIXME: When we grow m_value, we should represent the added bits as
187 // undefined somehow instead of as 0's.
188 if (value_type == Value::ValueType::HostAddress &&
189 compiler_type.IsValid()) {
190 if (size_t value_buf_size = m_value.GetBuffer().GetByteSize()) {
191 size_t value_size = m_value.GetValueByteSize(error_ptr: &m_error, exe_ctx: &exe_ctx);
192 if (m_error.Success() && value_buf_size < value_size)
193 m_value.ResizeData(len: value_size);
194 }
195 }
196
197 Process *process = exe_ctx.GetProcessPtr();
198 const bool process_is_alive = process && process->IsAlive();
199
200 switch (value_type) {
201 case Value::ValueType::Invalid:
202 m_error = Status::FromErrorString(str: "invalid value");
203 break;
204 case Value::ValueType::Scalar:
205 // The variable value is in the Scalar value inside the m_value. We can
206 // point our m_data right to it.
207 m_error = m_value.GetValueAsData(exe_ctx: &exe_ctx, data&: m_data, module: GetModule().get());
208 break;
209
210 case Value::ValueType::FileAddress:
211 case Value::ValueType::LoadAddress:
212 case Value::ValueType::HostAddress:
213 // The DWARF expression result was an address in the inferior process.
214 // If this variable is an aggregate type, we just need the address as
215 // the main value as all child variable objects will rely upon this
216 // location and add an offset and then read their own values as needed.
217 // If this variable is a simple type, we read all data for it into
218 // m_data. Make sure this type has a value before we try and read it
219
220 // If we have a file address, convert it to a load address if we can.
221 if (value_type == Value::ValueType::FileAddress && process_is_alive)
222 m_value.ConvertToLoadAddress(module: GetModule().get(), target);
223
224 if (!CanProvideValue()) {
225 // this value object represents an aggregate type whose children have
226 // values, but this object does not. So we say we are changed if our
227 // location has changed.
228 SetValueDidChange(value_type != old_value.GetValueType() ||
229 m_value.GetScalar() != old_value.GetScalar());
230 } else {
231 // Copy the Value and set the context to use our Variable so it can
232 // extract read its value into m_data appropriately
233 Value value(m_value);
234 value.SetContext(context_type: Value::ContextType::Variable, p: variable);
235 m_error = value.GetValueAsData(exe_ctx: &exe_ctx, data&: m_data, module: GetModule().get());
236
237 SetValueDidChange(value_type != old_value.GetValueType() ||
238 m_value.GetScalar() != old_value.GetScalar());
239 }
240 break;
241 }
242
243 SetValueIsValid(m_error.Success());
244 } else {
245 m_error = Status::FromError(error: maybe_value.takeError());
246 // could not find location, won't allow editing
247 m_resolved_value.SetContext(context_type: Value::ContextType::Invalid, p: nullptr);
248 }
249 }
250
251 return m_error.Success();
252}
253
254void ValueObjectVariable::DoUpdateChildrenAddressType(ValueObject &valobj) {
255 Value::ValueType value_type = valobj.GetValue().GetValueType();
256 ExecutionContext exe_ctx(GetExecutionContextRef());
257 Process *process = exe_ctx.GetProcessPtr();
258 const bool process_is_alive = process && process->IsAlive();
259 const uint32_t type_info = valobj.GetCompilerType().GetTypeInfo();
260 const bool is_pointer_or_ref =
261 (type_info & (lldb::eTypeIsPointer | lldb::eTypeIsReference)) != 0;
262
263 switch (value_type) {
264 case Value::ValueType::Invalid:
265 break;
266 case Value::ValueType::FileAddress:
267 // If this type is a pointer, then its children will be considered load
268 // addresses if the pointer or reference is dereferenced, but only if
269 // the process is alive.
270 //
271 // There could be global variables like in the following code:
272 // struct LinkedListNode { Foo* foo; LinkedListNode* next; };
273 // Foo g_foo1;
274 // Foo g_foo2;
275 // LinkedListNode g_second_node = { &g_foo2, NULL };
276 // LinkedListNode g_first_node = { &g_foo1, &g_second_node };
277 //
278 // When we aren't running, we should be able to look at these variables
279 // using the "target variable" command. Children of the "g_first_node"
280 // always will be of the same address type as the parent. But children
281 // of the "next" member of LinkedListNode will become load addresses if
282 // we have a live process, or remain a file address if it was a file
283 // address.
284 if (process_is_alive && is_pointer_or_ref)
285 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
286 else
287 valobj.SetAddressTypeOfChildren(eAddressTypeFile);
288 break;
289 case Value::ValueType::HostAddress:
290 // Same as above for load addresses, except children of pointer or refs
291 // are always load addresses. Host addresses are used to store freeze
292 // dried variables. If this type is a struct, the entire struct
293 // contents will be copied into the heap of the
294 // LLDB process, but we do not currently follow any pointers.
295 if (is_pointer_or_ref)
296 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
297 else
298 valobj.SetAddressTypeOfChildren(eAddressTypeHost);
299 break;
300 case Value::ValueType::LoadAddress:
301 case Value::ValueType::Scalar:
302 valobj.SetAddressTypeOfChildren(eAddressTypeLoad);
303 break;
304 }
305}
306
307bool ValueObjectVariable::IsInScope() {
308 const ExecutionContextRef &exe_ctx_ref = GetExecutionContextRef();
309 if (exe_ctx_ref.HasFrameRef()) {
310 ExecutionContext exe_ctx(exe_ctx_ref);
311 StackFrame *frame = exe_ctx.GetFramePtr();
312 if (frame) {
313 return m_variable_sp->IsInScope(frame);
314 } else {
315 // This ValueObject had a frame at one time, but now we can't locate it,
316 // so return false since we probably aren't in scope.
317 return false;
318 }
319 }
320 // We have a variable that wasn't tied to a frame, which means it is a global
321 // and is always in scope.
322 return true;
323}
324
325lldb::ModuleSP ValueObjectVariable::GetModule() {
326 if (m_variable_sp) {
327 SymbolContextScope *sc_scope = m_variable_sp->GetSymbolContextScope();
328 if (sc_scope) {
329 return sc_scope->CalculateSymbolContextModule();
330 }
331 }
332 return lldb::ModuleSP();
333}
334
335SymbolContextScope *ValueObjectVariable::GetSymbolContextScope() {
336 if (m_variable_sp)
337 return m_variable_sp->GetSymbolContextScope();
338 return nullptr;
339}
340
341bool ValueObjectVariable::GetDeclaration(Declaration &decl) {
342 if (m_variable_sp) {
343 decl = m_variable_sp->GetDeclaration();
344 return true;
345 }
346 return false;
347}
348
349const char *ValueObjectVariable::GetLocationAsCString() {
350 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo)
351 return GetLocationAsCStringImpl(value: m_resolved_value, data: m_data);
352 else
353 return ValueObject::GetLocationAsCString();
354}
355
356bool ValueObjectVariable::SetValueFromCString(const char *value_str,
357 Status &error) {
358 if (!UpdateValueIfNeeded()) {
359 error = Status::FromErrorString(str: "unable to update value before writing");
360 return false;
361 }
362
363 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
364 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
365 ExecutionContext exe_ctx(GetExecutionContextRef());
366 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
367 RegisterValue reg_value;
368 if (!reg_info || !reg_ctx) {
369 error = Status::FromErrorString(str: "unable to retrieve register info");
370 return false;
371 }
372 error = reg_value.SetValueFromString(reg_info, value_str: llvm::StringRef(value_str));
373 if (error.Fail())
374 return false;
375 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
376 SetNeedsUpdate();
377 return true;
378 } else {
379 error = Status::FromErrorString(str: "unable to write back to register");
380 return false;
381 }
382 } else
383 return ValueObject::SetValueFromCString(value_str, error);
384}
385
386bool ValueObjectVariable::SetData(DataExtractor &data, Status &error) {
387 if (!UpdateValueIfNeeded()) {
388 error = Status::FromErrorString(str: "unable to update value before writing");
389 return false;
390 }
391
392 if (m_resolved_value.GetContextType() == Value::ContextType::RegisterInfo) {
393 RegisterInfo *reg_info = m_resolved_value.GetRegisterInfo();
394 ExecutionContext exe_ctx(GetExecutionContextRef());
395 RegisterContext *reg_ctx = exe_ctx.GetRegisterContext();
396 RegisterValue reg_value;
397 if (!reg_info || !reg_ctx) {
398 error = Status::FromErrorString(str: "unable to retrieve register info");
399 return false;
400 }
401 error = reg_value.SetValueFromData(reg_info: *reg_info, data, offset: 0, partial_data_ok: true);
402 if (error.Fail())
403 return false;
404 if (reg_ctx->WriteRegister(reg_info, reg_value)) {
405 SetNeedsUpdate();
406 return true;
407 } else {
408 error = Status::FromErrorString(str: "unable to write back to register");
409 return false;
410 }
411 } else
412 return ValueObject::SetData(data, error);
413}
414

source code of lldb/source/ValueObject/ValueObjectVariable.cpp