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