1 //===-- LibCxx.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 "lldb/Core/Debugger.h"
12 #include "lldb/Core/FormatEntity.h"
13 #include "lldb/Core/ValueObject.h"
14 #include "lldb/Core/ValueObjectConstResult.h"
15 #include "lldb/DataFormatters/FormattersHelpers.h"
16 #include "lldb/DataFormatters/StringPrinter.h"
17 #include "lldb/DataFormatters/TypeSummary.h"
18 #include "lldb/DataFormatters/VectorIterator.h"
19 #include "lldb/Target/ProcessStructReader.h"
20 #include "lldb/Target/SectionLoadList.h"
21 #include "lldb/Target/Target.h"
22 #include "lldb/Utility/ConstString.h"
23 #include "lldb/Utility/DataBufferHeap.h"
24 #include "lldb/Utility/Endian.h"
25 #include "lldb/Utility/Status.h"
26 #include "lldb/Utility/Stream.h"
27 
28 #include "Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.h"
29 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
30 #include <tuple>
31 
32 using namespace lldb;
33 using namespace lldb_private;
34 using namespace lldb_private::formatters;
35 
36 bool lldb_private::formatters::LibcxxOptionalSummaryProvider(
37     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
38   ValueObjectSP valobj_sp(valobj.GetNonSyntheticValue());
39   if (!valobj_sp)
40     return false;
41 
42   // An optional either contains a value or not, the member __engaged_ is
43   // a bool flag, it is true if the optional has a value and false otherwise.
44   ValueObjectSP engaged_sp(
45       valobj_sp->GetChildMemberWithName(ConstString("__engaged_"), true));
46 
47   if (!engaged_sp)
48     return false;
49 
50   llvm::StringRef engaged_as_cstring(
51       engaged_sp->GetValueAsUnsigned(0) == 1 ? "true" : "false");
52 
53   stream.Printf(" Has Value=%s ", engaged_as_cstring.data());
54 
55   return true;
56 }
57 
58 bool lldb_private::formatters::LibcxxFunctionSummaryProvider(
59     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
60 
61   ValueObjectSP valobj_sp(valobj.GetNonSyntheticValue());
62 
63   if (!valobj_sp)
64     return false;
65 
66   ExecutionContext exe_ctx(valobj_sp->GetExecutionContextRef());
67   Process *process = exe_ctx.GetProcessPtr();
68 
69   if (process == nullptr)
70     return false;
71 
72   CPPLanguageRuntime *cpp_runtime = CPPLanguageRuntime::Get(*process);
73 
74   if (!cpp_runtime)
75     return false;
76 
77   CPPLanguageRuntime::LibCppStdFunctionCallableInfo callable_info =
78       cpp_runtime->FindLibCppStdFunctionCallableInfo(valobj_sp);
79 
80   switch (callable_info.callable_case) {
81   case CPPLanguageRuntime::LibCppStdFunctionCallableCase::Invalid:
82     stream.Printf(" __f_ = %" PRIu64, callable_info.member_f_pointer_value);
83     return false;
84     break;
85   case CPPLanguageRuntime::LibCppStdFunctionCallableCase::Lambda:
86     stream.Printf(
87         " Lambda in File %s at Line %u",
88         callable_info.callable_line_entry.file.GetFilename().GetCString(),
89         callable_info.callable_line_entry.line);
90     break;
91   case CPPLanguageRuntime::LibCppStdFunctionCallableCase::CallableObject:
92     stream.Printf(
93         " Function in File %s at Line %u",
94         callable_info.callable_line_entry.file.GetFilename().GetCString(),
95         callable_info.callable_line_entry.line);
96     break;
97   case CPPLanguageRuntime::LibCppStdFunctionCallableCase::FreeOrMemberFunction:
98     stream.Printf(" Function = %s ",
99                   callable_info.callable_symbol.GetName().GetCString());
100     break;
101   }
102 
103   return true;
104 }
105 
106 bool lldb_private::formatters::LibcxxSmartPointerSummaryProvider(
107     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
108   ValueObjectSP valobj_sp(valobj.GetNonSyntheticValue());
109   if (!valobj_sp)
110     return false;
111   ValueObjectSP ptr_sp(
112       valobj_sp->GetChildMemberWithName(ConstString("__ptr_"), true));
113   ValueObjectSP count_sp(valobj_sp->GetChildAtNamePath(
114       {ConstString("__cntrl_"), ConstString("__shared_owners_")}));
115   ValueObjectSP weakcount_sp(valobj_sp->GetChildAtNamePath(
116       {ConstString("__cntrl_"), ConstString("__shared_weak_owners_")}));
117 
118   if (!ptr_sp)
119     return false;
120 
121   if (ptr_sp->GetValueAsUnsigned(0) == 0) {
122     stream.Printf("nullptr");
123     return true;
124   } else {
125     bool print_pointee = false;
126     Status error;
127     ValueObjectSP pointee_sp = ptr_sp->Dereference(error);
128     if (pointee_sp && error.Success()) {
129       if (pointee_sp->DumpPrintableRepresentation(
130               stream, ValueObject::eValueObjectRepresentationStyleSummary,
131               lldb::eFormatInvalid,
132               ValueObject::PrintableRepresentationSpecialCases::eDisable,
133               false))
134         print_pointee = true;
135     }
136     if (!print_pointee)
137       stream.Printf("ptr = 0x%" PRIx64, ptr_sp->GetValueAsUnsigned(0));
138   }
139 
140   if (count_sp)
141     stream.Printf(" strong=%" PRIu64, 1 + count_sp->GetValueAsUnsigned(0));
142 
143   if (weakcount_sp)
144     stream.Printf(" weak=%" PRIu64, 1 + weakcount_sp->GetValueAsUnsigned(0));
145 
146   return true;
147 }
148 
149 bool lldb_private::formatters::LibcxxUniquePointerSummaryProvider(
150     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
151   ValueObjectSP valobj_sp(valobj.GetNonSyntheticValue());
152   if (!valobj_sp)
153     return false;
154 
155   ValueObjectSP ptr_sp(
156       valobj_sp->GetChildMemberWithName(ConstString("__ptr_"), true));
157   if (!ptr_sp)
158     return false;
159 
160   ptr_sp = GetValueOfLibCXXCompressedPair(*ptr_sp);
161   if (!ptr_sp)
162     return false;
163 
164   if (ptr_sp->GetValueAsUnsigned(0) == 0) {
165     stream.Printf("nullptr");
166     return true;
167   } else {
168     bool print_pointee = false;
169     Status error;
170     ValueObjectSP pointee_sp = ptr_sp->Dereference(error);
171     if (pointee_sp && error.Success()) {
172       if (pointee_sp->DumpPrintableRepresentation(
173               stream, ValueObject::eValueObjectRepresentationStyleSummary,
174               lldb::eFormatInvalid,
175               ValueObject::PrintableRepresentationSpecialCases::eDisable,
176               false))
177         print_pointee = true;
178     }
179     if (!print_pointee)
180       stream.Printf("ptr = 0x%" PRIx64, ptr_sp->GetValueAsUnsigned(0));
181   }
182 
183   return true;
184 }
185 
186 /*
187  (lldb) fr var ibeg --raw --ptr-depth 1
188  (std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int,
189  std::__1::basic_string<char, std::__1::char_traits<char>,
190  std::__1::allocator<char> > >, std::__1::__tree_node<std::__1::pair<int,
191  std::__1::basic_string<char, std::__1::char_traits<char>,
192  std::__1::allocator<char> > >, void *> *, long> >) ibeg = {
193  __i_ = {
194  __ptr_ = 0x0000000100103870 {
195  std::__1::__tree_node_base<void *> = {
196  std::__1::__tree_end_node<std::__1::__tree_node_base<void *> *> = {
197  __left_ = 0x0000000000000000
198  }
199  __right_ = 0x0000000000000000
200  __parent_ = 0x00000001001038b0
201  __is_black_ = true
202  }
203  __value_ = {
204  first = 0
205  second = { std::string }
206  */
207 
208 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
209     LibCxxMapIteratorSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
210     : SyntheticChildrenFrontEnd(*valobj_sp), m_pair_ptr(), m_pair_sp() {
211   if (valobj_sp)
212     Update();
213 }
214 
215 bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::Update() {
216   m_pair_sp.reset();
217   m_pair_ptr = nullptr;
218 
219   ValueObjectSP valobj_sp = m_backend.GetSP();
220   if (!valobj_sp)
221     return false;
222 
223   TargetSP target_sp(valobj_sp->GetTargetSP());
224 
225   if (!target_sp)
226     return false;
227 
228   if (!valobj_sp)
229     return false;
230 
231   static ConstString g_i_("__i_");
232 
233   // this must be a ValueObject* because it is a child of the ValueObject we
234   // are producing children for it if were a ValueObjectSP, we would end up
235   // with a loop (iterator -> synthetic -> child -> parent == iterator) and
236   // that would in turn leak memory by never allowing the ValueObjects to die
237   // and free their memory
238   m_pair_ptr = valobj_sp
239                    ->GetValueForExpressionPath(
240                        ".__i_.__ptr_->__value_", nullptr, nullptr,
241                        ValueObject::GetValueForExpressionPathOptions()
242                            .DontCheckDotVsArrowSyntax()
243                            .SetSyntheticChildrenTraversal(
244                                ValueObject::GetValueForExpressionPathOptions::
245                                    SyntheticChildrenTraversal::None),
246                        nullptr)
247                    .get();
248 
249   if (!m_pair_ptr) {
250     m_pair_ptr = valobj_sp
251                      ->GetValueForExpressionPath(
252                          ".__i_.__ptr_", nullptr, nullptr,
253                          ValueObject::GetValueForExpressionPathOptions()
254                              .DontCheckDotVsArrowSyntax()
255                              .SetSyntheticChildrenTraversal(
256                                  ValueObject::GetValueForExpressionPathOptions::
257                                      SyntheticChildrenTraversal::None),
258                          nullptr)
259                      .get();
260     if (m_pair_ptr) {
261       auto __i_(valobj_sp->GetChildMemberWithName(g_i_, true));
262       if (!__i_) {
263         m_pair_ptr = nullptr;
264         return false;
265       }
266       CompilerType pair_type(
267           __i_->GetCompilerType().GetTypeTemplateArgument(0));
268       std::string name;
269       uint64_t bit_offset_ptr;
270       uint32_t bitfield_bit_size_ptr;
271       bool is_bitfield_ptr;
272       pair_type = pair_type.GetFieldAtIndex(
273           0, name, &bit_offset_ptr, &bitfield_bit_size_ptr, &is_bitfield_ptr);
274       if (!pair_type) {
275         m_pair_ptr = nullptr;
276         return false;
277       }
278 
279       auto addr(m_pair_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS));
280       m_pair_ptr = nullptr;
281       if (addr && addr != LLDB_INVALID_ADDRESS) {
282         TypeSystemClang *ast_ctx =
283             llvm::dyn_cast_or_null<TypeSystemClang>(pair_type.GetTypeSystem());
284         if (!ast_ctx)
285           return false;
286         CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(
287             ConstString(),
288             {{"ptr0",
289               ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
290              {"ptr1",
291               ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
292              {"ptr2",
293               ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
294              {"cw", ast_ctx->GetBasicType(lldb::eBasicTypeBool)},
295              {"payload", pair_type}});
296         llvm::Optional<uint64_t> size = tree_node_type.GetByteSize(nullptr);
297         if (!size)
298           return false;
299         WritableDataBufferSP buffer_sp(new DataBufferHeap(*size, 0));
300         ProcessSP process_sp(target_sp->GetProcessSP());
301         Status error;
302         process_sp->ReadMemory(addr, buffer_sp->GetBytes(),
303                                buffer_sp->GetByteSize(), error);
304         if (error.Fail())
305           return false;
306         DataExtractor extractor(buffer_sp, process_sp->GetByteOrder(),
307                                 process_sp->GetAddressByteSize());
308         auto pair_sp = CreateValueObjectFromData(
309             "pair", extractor, valobj_sp->GetExecutionContextRef(),
310             tree_node_type);
311         if (pair_sp)
312           m_pair_sp = pair_sp->GetChildAtIndex(4, true);
313       }
314     }
315   }
316 
317   return false;
318 }
319 
320 size_t lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
321     CalculateNumChildren() {
322   return 2;
323 }
324 
325 lldb::ValueObjectSP
326 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::GetChildAtIndex(
327     size_t idx) {
328   if (m_pair_ptr)
329     return m_pair_ptr->GetChildAtIndex(idx, true);
330   if (m_pair_sp)
331     return m_pair_sp->GetChildAtIndex(idx, true);
332   return lldb::ValueObjectSP();
333 }
334 
335 bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
336     MightHaveChildren() {
337   return true;
338 }
339 
340 size_t lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
341     GetIndexOfChildWithName(ConstString name) {
342   if (name == "first")
343     return 0;
344   if (name == "second")
345     return 1;
346   return UINT32_MAX;
347 }
348 
349 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
350     ~LibCxxMapIteratorSyntheticFrontEnd() {
351   // this will be deleted when its parent dies (since it's a child object)
352   // delete m_pair_ptr;
353 }
354 
355 SyntheticChildrenFrontEnd *
356 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEndCreator(
357     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
358   return (valobj_sp ? new LibCxxMapIteratorSyntheticFrontEnd(valobj_sp)
359                     : nullptr);
360 }
361 
362 /*
363  (lldb) fr var ibeg --raw --ptr-depth 1 -T
364  (std::__1::__wrap_iter<int *>) ibeg = {
365  (std::__1::__wrap_iter<int *>::iterator_type) __i = 0x00000001001037a0 {
366  (int) *__i = 1
367  }
368  }
369 */
370 
371 SyntheticChildrenFrontEnd *
372 lldb_private::formatters::LibCxxVectorIteratorSyntheticFrontEndCreator(
373     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
374   static ConstString g_item_name;
375   if (!g_item_name)
376     g_item_name.SetCString("__i");
377   return (valobj_sp
378               ? new VectorIteratorSyntheticFrontEnd(valobj_sp, g_item_name)
379               : nullptr);
380 }
381 
382 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
383     LibcxxSharedPtrSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
384     : SyntheticChildrenFrontEnd(*valobj_sp), m_cntrl(nullptr) {
385   if (valobj_sp)
386     Update();
387 }
388 
389 size_t lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
390     CalculateNumChildren() {
391   return (m_cntrl ? 1 : 0);
392 }
393 
394 lldb::ValueObjectSP
395 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::GetChildAtIndex(
396     size_t idx) {
397   if (!m_cntrl)
398     return lldb::ValueObjectSP();
399 
400   ValueObjectSP valobj_sp = m_backend.GetSP();
401   if (!valobj_sp)
402     return lldb::ValueObjectSP();
403 
404   if (idx == 0)
405     return valobj_sp->GetChildMemberWithName(ConstString("__ptr_"), true);
406 
407   if (idx == 1) {
408     if (auto ptr_sp =
409             valobj_sp->GetChildMemberWithName(ConstString("__ptr_"), true)) {
410       Status status;
411       auto value_sp = ptr_sp->Dereference(status);
412       if (status.Success()) {
413         auto value_type_sp =
414             valobj_sp->GetCompilerType().GetTypeTemplateArgument(0);
415         return value_sp->Cast(value_type_sp);
416       }
417     }
418   }
419 
420   return lldb::ValueObjectSP();
421 }
422 
423 bool lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::Update() {
424   m_cntrl = nullptr;
425 
426   ValueObjectSP valobj_sp = m_backend.GetSP();
427   if (!valobj_sp)
428     return false;
429 
430   TargetSP target_sp(valobj_sp->GetTargetSP());
431   if (!target_sp)
432     return false;
433 
434   lldb::ValueObjectSP cntrl_sp(
435       valobj_sp->GetChildMemberWithName(ConstString("__cntrl_"), true));
436 
437   m_cntrl = cntrl_sp.get(); // need to store the raw pointer to avoid a circular
438                             // dependency
439   return false;
440 }
441 
442 bool lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
443     MightHaveChildren() {
444   return true;
445 }
446 
447 size_t lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
448     GetIndexOfChildWithName(ConstString name) {
449   if (name == "__ptr_")
450     return 0;
451   if (name == "$$dereference$$")
452     return 1;
453   return UINT32_MAX;
454 }
455 
456 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
457     ~LibcxxSharedPtrSyntheticFrontEnd() = default;
458 
459 SyntheticChildrenFrontEnd *
460 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEndCreator(
461     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
462   return (valobj_sp ? new LibcxxSharedPtrSyntheticFrontEnd(valobj_sp)
463                     : nullptr);
464 }
465 
466 lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEnd::
467     LibcxxUniquePtrSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
468     : SyntheticChildrenFrontEnd(*valobj_sp) {
469   if (valobj_sp)
470     Update();
471 }
472 
473 lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEnd::
474     ~LibcxxUniquePtrSyntheticFrontEnd() = default;
475 
476 SyntheticChildrenFrontEnd *
477 lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEndCreator(
478     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
479   return (valobj_sp ? new LibcxxUniquePtrSyntheticFrontEnd(valobj_sp)
480                     : nullptr);
481 }
482 
483 size_t lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEnd::
484     CalculateNumChildren() {
485   return (m_value_ptr_sp ? 1 : 0);
486 }
487 
488 lldb::ValueObjectSP
489 lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEnd::GetChildAtIndex(
490     size_t idx) {
491   if (!m_value_ptr_sp)
492     return lldb::ValueObjectSP();
493 
494   if (idx == 0)
495     return m_value_ptr_sp;
496 
497   if (idx == 1) {
498     Status status;
499     auto value_sp = m_value_ptr_sp->Dereference(status);
500     if (status.Success()) {
501       return value_sp;
502     }
503   }
504 
505   return lldb::ValueObjectSP();
506 }
507 
508 bool lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEnd::Update() {
509   ValueObjectSP valobj_sp = m_backend.GetSP();
510   if (!valobj_sp)
511     return false;
512 
513   ValueObjectSP ptr_sp(
514       valobj_sp->GetChildMemberWithName(ConstString("__ptr_"), true));
515   if (!ptr_sp)
516     return false;
517 
518   m_value_ptr_sp = GetValueOfLibCXXCompressedPair(*ptr_sp);
519 
520   return false;
521 }
522 
523 bool lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEnd::
524     MightHaveChildren() {
525   return true;
526 }
527 
528 size_t lldb_private::formatters::LibcxxUniquePtrSyntheticFrontEnd::
529     GetIndexOfChildWithName(ConstString name) {
530   if (name == "__value_")
531     return 0;
532   if (name == "$$dereference$$")
533     return 1;
534   return UINT32_MAX;
535 }
536 
537 bool lldb_private::formatters::LibcxxContainerSummaryProvider(
538     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
539   if (valobj.IsPointerType()) {
540     uint64_t value = valobj.GetValueAsUnsigned(0);
541     if (!value)
542       return false;
543     stream.Printf("0x%016" PRIx64 " ", value);
544   }
545   return FormatEntity::FormatStringRef("size=${svar%#}", stream, nullptr,
546                                        nullptr, nullptr, &valobj, false, false);
547 }
548 
549 // the field layout in a libc++ string (cap, side, data or data, size, cap)
550 enum LibcxxStringLayoutMode {
551   eLibcxxStringLayoutModeCSD = 0,
552   eLibcxxStringLayoutModeDSC = 1,
553   eLibcxxStringLayoutModeInvalid = 0xffff
554 };
555 
556 /// Determine the size in bytes of \p valobj (a libc++ std::string object) and
557 /// extract its data payload. Return the size + payload pair.
558 // TODO: Support big-endian architectures.
559 static llvm::Optional<std::pair<uint64_t, ValueObjectSP>>
560 ExtractLibcxxStringInfo(ValueObject &valobj) {
561   ValueObjectSP D(valobj.GetChildAtIndexPath({0, 0, 0, 0}));
562   if (!D)
563     return {};
564 
565   ValueObjectSP layout_decider(
566       D->GetChildAtIndexPath(llvm::ArrayRef<size_t>({0, 0})));
567 
568   // this child should exist
569   if (!layout_decider)
570     return {};
571 
572   ConstString g_data_name("__data_");
573   ConstString g_size_name("__size_");
574   bool short_mode = false; // this means the string is in short-mode and the
575                            // data is stored inline
576   bool using_bitmasks = true; // Whether the class uses bitmasks for the mode
577                               // flag (pre-D123580).
578   uint64_t size;
579   LibcxxStringLayoutMode layout = (layout_decider->GetName() == g_data_name)
580                                       ? eLibcxxStringLayoutModeDSC
581                                       : eLibcxxStringLayoutModeCSD;
582   uint64_t size_mode_value = 0;
583 
584   if (ValueObjectSP is_long = D->GetChildAtNamePath(
585           {ConstString("__s"), ConstString("__is_long_")})) {
586     using_bitmasks = false;
587     short_mode = !is_long->GetValueAsUnsigned(/*fail_value=*/0);
588     if (ValueObjectSP size_member =
589             D->GetChildAtNamePath({ConstString("__s"), ConstString("__size_")}))
590       size = size_member->GetValueAsUnsigned(/*fail_value=*/0);
591     else
592       return {};
593   } else if (layout == eLibcxxStringLayoutModeDSC) {
594     llvm::SmallVector<size_t, 3> size_mode_locations[] = {
595         {1, 2}, // Post-c3d0205ee771 layout. This was in use for only a brief
596                 // period, so we can delete it if it becomes a burden.
597         {1, 1, 0},
598         {1, 1, 1},
599     };
600     ValueObjectSP size_mode;
601     for (llvm::ArrayRef<size_t> loc : size_mode_locations) {
602       size_mode = D->GetChildAtIndexPath(loc);
603       if (size_mode && size_mode->GetName() == g_size_name)
604         break;
605     }
606 
607     if (!size_mode)
608       return {};
609 
610     size_mode_value = (size_mode->GetValueAsUnsigned(0));
611     short_mode = ((size_mode_value & 0x80) == 0);
612   } else {
613     ValueObjectSP size_mode(D->GetChildAtIndexPath({1, 0, 0}));
614     if (!size_mode)
615       return {};
616 
617     size_mode_value = (size_mode->GetValueAsUnsigned(0));
618     short_mode = ((size_mode_value & 1) == 0);
619   }
620 
621   if (short_mode) {
622     ValueObjectSP s(D->GetChildAtIndex(1, true));
623     if (!s)
624       return {};
625     ValueObjectSP location_sp = s->GetChildAtIndex(
626         (layout == eLibcxxStringLayoutModeDSC) ? 0 : 1, true);
627     if (using_bitmasks)
628       size = (layout == eLibcxxStringLayoutModeDSC)
629                  ? size_mode_value
630                  : ((size_mode_value >> 1) % 256);
631 
632     // When the small-string optimization takes place, the data must fit in the
633     // inline string buffer (23 bytes on x86_64/Darwin). If it doesn't, it's
634     // likely that the string isn't initialized and we're reading garbage.
635     ExecutionContext exe_ctx(location_sp->GetExecutionContextRef());
636     const llvm::Optional<uint64_t> max_bytes =
637         location_sp->GetCompilerType().GetByteSize(
638             exe_ctx.GetBestExecutionContextScope());
639     if (!max_bytes || size > *max_bytes || !location_sp)
640       return {};
641 
642     return std::make_pair(size, location_sp);
643   }
644 
645   ValueObjectSP l(D->GetChildAtIndex(0, true));
646   if (!l)
647     return {};
648   // we can use the layout_decider object as the data pointer
649   ValueObjectSP location_sp =
650       l->GetChildMemberWithName(ConstString("__data_"), /*can_create=*/true);
651   ValueObjectSP size_vo =
652       l->GetChildMemberWithName(ConstString("__size_"), /*can_create=*/true);
653   ValueObjectSP capacity_vo =
654       l->GetChildMemberWithName(ConstString("__cap_"), /*can_create=*/true);
655   if (!size_vo || !location_sp || !capacity_vo)
656     return {};
657   size = size_vo->GetValueAsUnsigned(LLDB_INVALID_OFFSET);
658   uint64_t capacity = capacity_vo->GetValueAsUnsigned(LLDB_INVALID_OFFSET);
659   if (!using_bitmasks && layout == eLibcxxStringLayoutModeCSD)
660     capacity *= 2;
661   if (size == LLDB_INVALID_OFFSET || capacity == LLDB_INVALID_OFFSET ||
662       capacity < size)
663     return {};
664   return std::make_pair(size, location_sp);
665 }
666 
667 static bool
668 LibcxxWStringSummaryProvider(ValueObject &valobj, Stream &stream,
669                              const TypeSummaryOptions &summary_options,
670                              ValueObjectSP location_sp, size_t size) {
671   if (size == 0) {
672     stream.Printf("L\"\"");
673     return true;
674   }
675   if (!location_sp)
676     return false;
677 
678   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
679   if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
680     const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
681     if (size > max_size) {
682       size = max_size;
683       options.SetIsTruncated(true);
684     }
685   }
686 
687   DataExtractor extractor;
688   const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
689   if (bytes_read < size)
690     return false;
691 
692   // std::wstring::size() is measured in 'characters', not bytes
693   TypeSystemClang *ast_context =
694       ScratchTypeSystemClang::GetForTarget(*valobj.GetTargetSP());
695   if (!ast_context)
696     return false;
697 
698   auto wchar_t_size =
699       ast_context->GetBasicType(lldb::eBasicTypeWChar).GetByteSize(nullptr);
700   if (!wchar_t_size)
701     return false;
702 
703   options.SetData(std::move(extractor));
704   options.SetStream(&stream);
705   options.SetPrefixToken("L");
706   options.SetQuote('"');
707   options.SetSourceSize(size);
708   options.SetBinaryZeroIsTerminator(false);
709 
710   switch (*wchar_t_size) {
711   case 1:
712     return StringPrinter::ReadBufferAndDumpToStream<
713         lldb_private::formatters::StringPrinter::StringElementType::UTF8>(
714         options);
715     break;
716 
717   case 2:
718     return StringPrinter::ReadBufferAndDumpToStream<
719         lldb_private::formatters::StringPrinter::StringElementType::UTF16>(
720         options);
721     break;
722 
723   case 4:
724     return StringPrinter::ReadBufferAndDumpToStream<
725         lldb_private::formatters::StringPrinter::StringElementType::UTF32>(
726         options);
727   }
728   return false;
729 }
730 
731 bool lldb_private::formatters::LibcxxWStringSummaryProvider(
732     ValueObject &valobj, Stream &stream,
733     const TypeSummaryOptions &summary_options) {
734   auto string_info = ExtractLibcxxStringInfo(valobj);
735   if (!string_info)
736     return false;
737   uint64_t size;
738   ValueObjectSP location_sp;
739   std::tie(size, location_sp) = *string_info;
740 
741   return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
742                                         location_sp, size);
743 }
744 
745 template <StringPrinter::StringElementType element_type>
746 static bool
747 LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
748                             const TypeSummaryOptions &summary_options,
749                             std::string prefix_token, ValueObjectSP location_sp,
750                             uint64_t size) {
751 
752   if (size == 0) {
753     stream.Printf("\"\"");
754     return true;
755   }
756 
757   if (!location_sp)
758     return false;
759 
760   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
761 
762   if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
763     const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
764     if (size > max_size) {
765       size = max_size;
766       options.SetIsTruncated(true);
767     }
768   }
769 
770   {
771     DataExtractor extractor;
772     const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
773     if (bytes_read < size)
774       return false;
775 
776     options.SetData(std::move(extractor));
777   }
778   options.SetStream(&stream);
779   if (prefix_token.empty())
780     options.SetPrefixToken(nullptr);
781   else
782     options.SetPrefixToken(prefix_token);
783   options.SetQuote('"');
784   options.SetSourceSize(size);
785   options.SetBinaryZeroIsTerminator(false);
786   return StringPrinter::ReadBufferAndDumpToStream<element_type>(options);
787 }
788 
789 template <StringPrinter::StringElementType element_type>
790 static bool
791 LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
792                             const TypeSummaryOptions &summary_options,
793                             std::string prefix_token) {
794   auto string_info = ExtractLibcxxStringInfo(valobj);
795   if (!string_info)
796     return false;
797   uint64_t size;
798   ValueObjectSP location_sp;
799   std::tie(size, location_sp) = *string_info;
800 
801   return LibcxxStringSummaryProvider<element_type>(
802       valobj, stream, summary_options, prefix_token, location_sp, size);
803 }
804 template <StringPrinter::StringElementType element_type>
805 static bool formatStringImpl(ValueObject &valobj, Stream &stream,
806                              const TypeSummaryOptions &summary_options,
807                              std::string prefix_token) {
808   StreamString scratch_stream;
809   const bool success = LibcxxStringSummaryProvider<element_type>(
810       valobj, scratch_stream, summary_options, prefix_token);
811   if (success)
812     stream << scratch_stream.GetData();
813   else
814     stream << "Summary Unavailable";
815   return true;
816 }
817 
818 bool lldb_private::formatters::LibcxxStringSummaryProviderASCII(
819     ValueObject &valobj, Stream &stream,
820     const TypeSummaryOptions &summary_options) {
821   return formatStringImpl<StringPrinter::StringElementType::ASCII>(
822       valobj, stream, summary_options, "");
823 }
824 
825 bool lldb_private::formatters::LibcxxStringSummaryProviderUTF16(
826     ValueObject &valobj, Stream &stream,
827     const TypeSummaryOptions &summary_options) {
828   return formatStringImpl<StringPrinter::StringElementType::UTF16>(
829       valobj, stream, summary_options, "u");
830 }
831 
832 bool lldb_private::formatters::LibcxxStringSummaryProviderUTF32(
833     ValueObject &valobj, Stream &stream,
834     const TypeSummaryOptions &summary_options) {
835   return formatStringImpl<StringPrinter::StringElementType::UTF32>(
836       valobj, stream, summary_options, "U");
837 }
838 
839 static std::tuple<bool, ValueObjectSP, size_t>
840 LibcxxExtractStringViewData(ValueObject& valobj) {
841   ConstString g_data_name("__data");
842   ConstString g_size_name("__size");
843   auto dataobj = valobj.GetChildMemberWithName(g_data_name, true);
844   auto sizeobj = valobj.GetChildMemberWithName(g_size_name, true);
845 
846   if (!dataobj || !sizeobj)
847     return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
848 
849   if (!dataobj->GetError().Success() || !sizeobj->GetError().Success())
850     return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
851 
852   bool success{false};
853   uint64_t size = sizeobj->GetValueAsUnsigned(0, &success);
854   if (!success)
855     return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
856 
857   return std::make_tuple(true,dataobj,size);
858 }
859 
860 template <StringPrinter::StringElementType element_type>
861 static bool formatStringViewImpl(ValueObject &valobj, Stream &stream,
862                                  const TypeSummaryOptions &summary_options,
863                                  std::string prefix_token) {
864 
865   bool success;
866   ValueObjectSP dataobj;
867   size_t size;
868   std::tie(success, dataobj, size) = LibcxxExtractStringViewData(valobj);
869 
870   if (!success) {
871     stream << "Summary Unavailable";
872     return true;
873   }
874 
875   return LibcxxStringSummaryProvider<element_type>(
876       valobj, stream, summary_options, prefix_token, dataobj, size);
877 }
878 
879 bool lldb_private::formatters::LibcxxStringViewSummaryProviderASCII(
880     ValueObject &valobj, Stream &stream,
881     const TypeSummaryOptions &summary_options) {
882   return formatStringViewImpl<StringPrinter::StringElementType::ASCII>(
883       valobj, stream, summary_options, "");
884 }
885 
886 bool lldb_private::formatters::LibcxxStringViewSummaryProviderUTF16(
887     ValueObject &valobj, Stream &stream,
888     const TypeSummaryOptions &summary_options) {
889   return formatStringViewImpl<StringPrinter::StringElementType::UTF16>(
890       valobj, stream, summary_options, "u");
891 }
892 
893 bool lldb_private::formatters::LibcxxStringViewSummaryProviderUTF32(
894     ValueObject &valobj, Stream &stream,
895     const TypeSummaryOptions &summary_options) {
896   return formatStringViewImpl<StringPrinter::StringElementType::UTF32>(
897       valobj, stream, summary_options, "U");
898 }
899 
900 bool lldb_private::formatters::LibcxxWStringViewSummaryProvider(
901     ValueObject &valobj, Stream &stream,
902     const TypeSummaryOptions &summary_options) {
903 
904   bool success;
905   ValueObjectSP dataobj;
906   size_t size;
907   std::tie( success, dataobj, size ) = LibcxxExtractStringViewData(valobj);
908 
909   if (!success) {
910     stream << "Summary Unavailable";
911     return true;
912   }
913 
914 
915   return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
916                                         dataobj, size);
917 }
918