1 //===-- LibCxxList.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
11 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
12 #include "lldb/Core/ValueObject.h"
13 #include "lldb/Core/ValueObjectConstResult.h"
14 #include "lldb/DataFormatters/FormattersHelpers.h"
15 #include "lldb/Target/Target.h"
16 #include "lldb/Utility/DataBufferHeap.h"
17 #include "lldb/Utility/Endian.h"
18 #include "lldb/Utility/Status.h"
19 #include "lldb/Utility/Stream.h"
20
21 using namespace lldb;
22 using namespace lldb_private;
23 using namespace lldb_private::formatters;
24
25 namespace {
26
27 class ListEntry {
28 public:
29 ListEntry() = default;
ListEntry(ValueObjectSP entry_sp)30 ListEntry(ValueObjectSP entry_sp) : m_entry_sp(std::move(entry_sp)) {}
ListEntry(ValueObject * entry)31 ListEntry(ValueObject *entry)
32 : m_entry_sp(entry ? entry->GetSP() : ValueObjectSP()) {}
33
next()34 ListEntry next() {
35 if (!m_entry_sp)
36 return ListEntry();
37 return ListEntry(m_entry_sp->GetChildMemberWithName("__next_"));
38 }
39
prev()40 ListEntry prev() {
41 if (!m_entry_sp)
42 return ListEntry();
43 return ListEntry(m_entry_sp->GetChildMemberWithName("__prev_"));
44 }
45
value() const46 uint64_t value() const {
47 if (!m_entry_sp)
48 return 0;
49 return m_entry_sp->GetValueAsUnsigned(0);
50 }
51
null()52 bool null() { return (value() == 0); }
53
operator bool()54 explicit operator bool() { return GetEntry() && !null(); }
55
GetEntry()56 ValueObjectSP GetEntry() { return m_entry_sp; }
57
SetEntry(ValueObjectSP entry)58 void SetEntry(ValueObjectSP entry) { m_entry_sp = entry; }
59
operator ==(const ListEntry & rhs) const60 bool operator==(const ListEntry &rhs) const { return value() == rhs.value(); }
61
operator !=(const ListEntry & rhs) const62 bool operator!=(const ListEntry &rhs) const { return !(*this == rhs); }
63
64 private:
65 ValueObjectSP m_entry_sp;
66 };
67
68 class ListIterator {
69 public:
70 ListIterator() = default;
ListIterator(ListEntry entry)71 ListIterator(ListEntry entry) : m_entry(std::move(entry)) {}
ListIterator(ValueObjectSP entry)72 ListIterator(ValueObjectSP entry) : m_entry(std::move(entry)) {}
ListIterator(ValueObject * entry)73 ListIterator(ValueObject *entry) : m_entry(entry) {}
74
value()75 ValueObjectSP value() { return m_entry.GetEntry(); }
76
advance(size_t count)77 ValueObjectSP advance(size_t count) {
78 if (count == 0)
79 return m_entry.GetEntry();
80 if (count == 1) {
81 next();
82 return m_entry.GetEntry();
83 }
84 while (count > 0) {
85 next();
86 count--;
87 if (m_entry.null())
88 return lldb::ValueObjectSP();
89 }
90 return m_entry.GetEntry();
91 }
92
operator ==(const ListIterator & rhs) const93 bool operator==(const ListIterator &rhs) const {
94 return (rhs.m_entry == m_entry);
95 }
96
97 protected:
next()98 void next() { m_entry = m_entry.next(); }
99
prev()100 void prev() { m_entry = m_entry.prev(); }
101
102 private:
103 ListEntry m_entry;
104 };
105
106 class AbstractListFrontEnd : public SyntheticChildrenFrontEnd {
107 public:
GetIndexOfChildWithName(ConstString name)108 size_t GetIndexOfChildWithName(ConstString name) override {
109 return ExtractIndexFromString(name.GetCString());
110 }
MightHaveChildren()111 bool MightHaveChildren() override { return true; }
112 lldb::ChildCacheState Update() override;
113
114 protected:
AbstractListFrontEnd(ValueObject & valobj)115 AbstractListFrontEnd(ValueObject &valobj)
116 : SyntheticChildrenFrontEnd(valobj) {}
117
118 size_t m_count = 0;
119 ValueObject *m_head = nullptr;
120
121 static constexpr bool g_use_loop_detect = true;
122 size_t m_loop_detected = 0; // The number of elements that have had loop
123 // detection run over them.
124 ListEntry m_slow_runner; // Used for loop detection
125 ListEntry m_fast_runner; // Used for loop detection
126
127 size_t m_list_capping_size = 0;
128 CompilerType m_element_type;
129 std::map<size_t, ListIterator> m_iterators;
130
131 bool HasLoop(size_t count);
132 ValueObjectSP GetItem(size_t idx);
133 };
134
135 class ForwardListFrontEnd : public AbstractListFrontEnd {
136 public:
137 ForwardListFrontEnd(ValueObject &valobj);
138
139 llvm::Expected<uint32_t> CalculateNumChildren() override;
140 ValueObjectSP GetChildAtIndex(uint32_t idx) override;
141 lldb::ChildCacheState Update() override;
142 };
143
144 class ListFrontEnd : public AbstractListFrontEnd {
145 public:
146 ListFrontEnd(lldb::ValueObjectSP valobj_sp);
147
148 ~ListFrontEnd() override = default;
149
150 llvm::Expected<uint32_t> CalculateNumChildren() override;
151
152 lldb::ValueObjectSP GetChildAtIndex(uint32_t idx) override;
153
154 lldb::ChildCacheState Update() override;
155
156 private:
157 lldb::addr_t m_node_address = 0;
158 ValueObject *m_tail = nullptr;
159 };
160
161 } // end anonymous namespace
162
Update()163 lldb::ChildCacheState AbstractListFrontEnd::Update() {
164 m_loop_detected = 0;
165 m_count = UINT32_MAX;
166 m_head = nullptr;
167 m_list_capping_size = 0;
168 m_slow_runner.SetEntry(nullptr);
169 m_fast_runner.SetEntry(nullptr);
170 m_iterators.clear();
171
172 if (m_backend.GetTargetSP())
173 m_list_capping_size =
174 m_backend.GetTargetSP()->GetMaximumNumberOfChildrenToDisplay();
175 if (m_list_capping_size == 0)
176 m_list_capping_size = 255;
177
178 CompilerType list_type = m_backend.GetCompilerType();
179 if (list_type.IsReferenceType())
180 list_type = list_type.GetNonReferenceType();
181
182 if (list_type.GetNumTemplateArguments() == 0)
183 return lldb::ChildCacheState::eRefetch;
184 m_element_type = list_type.GetTypeTemplateArgument(0);
185
186 return lldb::ChildCacheState::eRefetch;
187 }
188
HasLoop(size_t count)189 bool AbstractListFrontEnd::HasLoop(size_t count) {
190 if (!g_use_loop_detect)
191 return false;
192 // don't bother checking for a loop if we won't actually need to jump nodes
193 if (m_count < 2)
194 return false;
195
196 if (m_loop_detected == 0) {
197 // This is the first time we are being run (after the last update). Set up
198 // the loop invariant for the first element.
199 m_slow_runner = ListEntry(m_head).next();
200 m_fast_runner = m_slow_runner.next();
201 m_loop_detected = 1;
202 }
203
204 // Loop invariant:
205 // Loop detection has been run over the first m_loop_detected elements. If
206 // m_slow_runner == m_fast_runner then the loop has been detected after
207 // m_loop_detected elements.
208 const size_t steps_to_run = std::min(count, m_count);
209 while (m_loop_detected < steps_to_run && m_slow_runner && m_fast_runner &&
210 m_slow_runner != m_fast_runner) {
211
212 m_slow_runner = m_slow_runner.next();
213 m_fast_runner = m_fast_runner.next().next();
214 m_loop_detected++;
215 }
216 if (count <= m_loop_detected)
217 return false; // No loop in the first m_loop_detected elements.
218 if (!m_slow_runner || !m_fast_runner)
219 return false; // Reached the end of the list. Definitely no loops.
220 return m_slow_runner == m_fast_runner;
221 }
222
GetItem(size_t idx)223 ValueObjectSP AbstractListFrontEnd::GetItem(size_t idx) {
224 size_t advance = idx;
225 ListIterator current(m_head);
226 if (idx > 0) {
227 auto cached_iterator = m_iterators.find(idx - 1);
228 if (cached_iterator != m_iterators.end()) {
229 current = cached_iterator->second;
230 advance = 1;
231 }
232 }
233 ValueObjectSP value_sp = current.advance(advance);
234 m_iterators[idx] = current;
235 return value_sp;
236 }
237
ForwardListFrontEnd(ValueObject & valobj)238 ForwardListFrontEnd::ForwardListFrontEnd(ValueObject &valobj)
239 : AbstractListFrontEnd(valobj) {
240 Update();
241 }
242
CalculateNumChildren()243 llvm::Expected<uint32_t> ForwardListFrontEnd::CalculateNumChildren() {
244 if (m_count != UINT32_MAX)
245 return m_count;
246
247 ListEntry current(m_head);
248 m_count = 0;
249 while (current && m_count < m_list_capping_size) {
250 ++m_count;
251 current = current.next();
252 }
253 return m_count;
254 }
255
GetChildAtIndex(uint32_t idx)256 ValueObjectSP ForwardListFrontEnd::GetChildAtIndex(uint32_t idx) {
257 if (idx >= CalculateNumChildrenIgnoringErrors())
258 return nullptr;
259
260 if (!m_head)
261 return nullptr;
262
263 if (HasLoop(idx + 1))
264 return nullptr;
265
266 ValueObjectSP current_sp = GetItem(idx);
267 if (!current_sp)
268 return nullptr;
269
270 current_sp = current_sp->GetChildAtIndex(1); // get the __value_ child
271 if (!current_sp)
272 return nullptr;
273
274 // we need to copy current_sp into a new object otherwise we will end up with
275 // all items named __value_
276 DataExtractor data;
277 Status error;
278 current_sp->GetData(data, error);
279 if (error.Fail())
280 return nullptr;
281
282 return CreateValueObjectFromData(llvm::formatv("[{0}]", idx).str(), data,
283 m_backend.GetExecutionContextRef(),
284 m_element_type);
285 }
286
Update()287 lldb::ChildCacheState ForwardListFrontEnd::Update() {
288 AbstractListFrontEnd::Update();
289
290 Status err;
291 ValueObjectSP backend_addr(m_backend.AddressOf(err));
292 if (err.Fail() || !backend_addr)
293 return lldb::ChildCacheState::eRefetch;
294
295 ValueObjectSP impl_sp(m_backend.GetChildMemberWithName("__before_begin_"));
296 if (!impl_sp)
297 return lldb::ChildCacheState::eRefetch;
298 impl_sp = GetFirstValueOfLibCXXCompressedPair(*impl_sp);
299 if (!impl_sp)
300 return lldb::ChildCacheState::eRefetch;
301 m_head = impl_sp->GetChildMemberWithName("__next_").get();
302 return lldb::ChildCacheState::eRefetch;
303 }
304
ListFrontEnd(lldb::ValueObjectSP valobj_sp)305 ListFrontEnd::ListFrontEnd(lldb::ValueObjectSP valobj_sp)
306 : AbstractListFrontEnd(*valobj_sp) {
307 if (valobj_sp)
308 Update();
309 }
310
CalculateNumChildren()311 llvm::Expected<uint32_t> ListFrontEnd::CalculateNumChildren() {
312 if (m_count != UINT32_MAX)
313 return m_count;
314 if (!m_head || !m_tail || m_node_address == 0)
315 return 0;
316 ValueObjectSP size_alloc(m_backend.GetChildMemberWithName("__size_alloc_"));
317 if (size_alloc) {
318 ValueObjectSP value = GetFirstValueOfLibCXXCompressedPair(*size_alloc);
319 if (value) {
320 m_count = value->GetValueAsUnsigned(UINT32_MAX);
321 }
322 }
323 if (m_count != UINT32_MAX) {
324 return m_count;
325 } else {
326 uint64_t next_val = m_head->GetValueAsUnsigned(0);
327 uint64_t prev_val = m_tail->GetValueAsUnsigned(0);
328 if (next_val == 0 || prev_val == 0)
329 return 0;
330 if (next_val == m_node_address)
331 return 0;
332 if (next_val == prev_val)
333 return 1;
334 uint64_t size = 2;
335 ListEntry current(m_head);
336 while (current.next() && current.next().value() != m_node_address) {
337 size++;
338 current = current.next();
339 if (size > m_list_capping_size)
340 break;
341 }
342 return m_count = (size - 1);
343 }
344 }
345
GetChildAtIndex(uint32_t idx)346 lldb::ValueObjectSP ListFrontEnd::GetChildAtIndex(uint32_t idx) {
347 static ConstString g_value("__value_");
348 static ConstString g_next("__next_");
349
350 if (idx >= CalculateNumChildrenIgnoringErrors())
351 return lldb::ValueObjectSP();
352
353 if (!m_head || !m_tail || m_node_address == 0)
354 return lldb::ValueObjectSP();
355
356 if (HasLoop(idx + 1))
357 return lldb::ValueObjectSP();
358
359 ValueObjectSP current_sp = GetItem(idx);
360 if (!current_sp)
361 return lldb::ValueObjectSP();
362
363 current_sp = current_sp->GetChildAtIndex(1); // get the __value_ child
364 if (!current_sp)
365 return lldb::ValueObjectSP();
366
367 if (current_sp->GetName() == g_next) {
368 ProcessSP process_sp(current_sp->GetProcessSP());
369 if (!process_sp)
370 return lldb::ValueObjectSP();
371
372 // if we grabbed the __next_ pointer, then the child is one pointer deep-er
373 lldb::addr_t addr = current_sp->GetParent()->GetPointerValue();
374 addr = addr + 2 * process_sp->GetAddressByteSize();
375 ExecutionContext exe_ctx(process_sp);
376 current_sp =
377 CreateValueObjectFromAddress("__value_", addr, exe_ctx, m_element_type);
378 if (!current_sp)
379 return lldb::ValueObjectSP();
380 }
381
382 // we need to copy current_sp into a new object otherwise we will end up with
383 // all items named __value_
384 DataExtractor data;
385 Status error;
386 current_sp->GetData(data, error);
387 if (error.Fail())
388 return lldb::ValueObjectSP();
389
390 StreamString name;
391 name.Printf("[%" PRIu64 "]", (uint64_t)idx);
392 return CreateValueObjectFromData(name.GetString(), data,
393 m_backend.GetExecutionContextRef(),
394 m_element_type);
395 }
396
Update()397 lldb::ChildCacheState ListFrontEnd::Update() {
398 AbstractListFrontEnd::Update();
399 m_tail = nullptr;
400 m_node_address = 0;
401
402 Status err;
403 ValueObjectSP backend_addr(m_backend.AddressOf(err));
404 if (err.Fail() || !backend_addr)
405 return lldb::ChildCacheState::eRefetch;
406 m_node_address = backend_addr->GetValueAsUnsigned(0);
407 if (!m_node_address || m_node_address == LLDB_INVALID_ADDRESS)
408 return lldb::ChildCacheState::eRefetch;
409 ValueObjectSP impl_sp(m_backend.GetChildMemberWithName("__end_"));
410 if (!impl_sp)
411 return lldb::ChildCacheState::eRefetch;
412 m_head = impl_sp->GetChildMemberWithName("__next_").get();
413 m_tail = impl_sp->GetChildMemberWithName("__prev_").get();
414 return lldb::ChildCacheState::eRefetch;
415 }
416
LibcxxStdListSyntheticFrontEndCreator(CXXSyntheticChildren *,lldb::ValueObjectSP valobj_sp)417 SyntheticChildrenFrontEnd *formatters::LibcxxStdListSyntheticFrontEndCreator(
418 CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
419 return (valobj_sp ? new ListFrontEnd(valobj_sp) : nullptr);
420 }
421
422 SyntheticChildrenFrontEnd *
LibcxxStdForwardListSyntheticFrontEndCreator(CXXSyntheticChildren *,lldb::ValueObjectSP valobj_sp)423 formatters::LibcxxStdForwardListSyntheticFrontEndCreator(
424 CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
425 return valobj_sp ? new ForwardListFrontEnd(*valobj_sp) : nullptr;
426 }
427