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 /*
148  (lldb) fr var ibeg --raw --ptr-depth 1
149  (std::__1::__map_iterator<std::__1::__tree_iterator<std::__1::pair<int,
150  std::__1::basic_string<char, std::__1::char_traits<char>,
151  std::__1::allocator<char> > >, std::__1::__tree_node<std::__1::pair<int,
152  std::__1::basic_string<char, std::__1::char_traits<char>,
153  std::__1::allocator<char> > >, void *> *, long> >) ibeg = {
154  __i_ = {
155  __ptr_ = 0x0000000100103870 {
156  std::__1::__tree_node_base<void *> = {
157  std::__1::__tree_end_node<std::__1::__tree_node_base<void *> *> = {
158  __left_ = 0x0000000000000000
159  }
160  __right_ = 0x0000000000000000
161  __parent_ = 0x00000001001038b0
162  __is_black_ = true
163  }
164  __value_ = {
165  first = 0
166  second = { std::string }
167  */
168 
169 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
170     LibCxxMapIteratorSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
171     : SyntheticChildrenFrontEnd(*valobj_sp), m_pair_ptr(), m_pair_sp() {
172   if (valobj_sp)
173     Update();
174 }
175 
176 bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::Update() {
177   m_pair_sp.reset();
178   m_pair_ptr = nullptr;
179 
180   ValueObjectSP valobj_sp = m_backend.GetSP();
181   if (!valobj_sp)
182     return false;
183 
184   TargetSP target_sp(valobj_sp->GetTargetSP());
185 
186   if (!target_sp)
187     return false;
188 
189   if (!valobj_sp)
190     return false;
191 
192   static ConstString g___i_("__i_");
193 
194   // this must be a ValueObject* because it is a child of the ValueObject we
195   // are producing children for it if were a ValueObjectSP, we would end up
196   // with a loop (iterator -> synthetic -> child -> parent == iterator) and
197   // that would in turn leak memory by never allowing the ValueObjects to die
198   // and free their memory
199   m_pair_ptr = valobj_sp
200                    ->GetValueForExpressionPath(
201                        ".__i_.__ptr_->__value_", nullptr, nullptr,
202                        ValueObject::GetValueForExpressionPathOptions()
203                            .DontCheckDotVsArrowSyntax()
204                            .SetSyntheticChildrenTraversal(
205                                ValueObject::GetValueForExpressionPathOptions::
206                                    SyntheticChildrenTraversal::None),
207                        nullptr)
208                    .get();
209 
210   if (!m_pair_ptr) {
211     m_pair_ptr = valobj_sp
212                      ->GetValueForExpressionPath(
213                          ".__i_.__ptr_", nullptr, nullptr,
214                          ValueObject::GetValueForExpressionPathOptions()
215                              .DontCheckDotVsArrowSyntax()
216                              .SetSyntheticChildrenTraversal(
217                                  ValueObject::GetValueForExpressionPathOptions::
218                                      SyntheticChildrenTraversal::None),
219                          nullptr)
220                      .get();
221     if (m_pair_ptr) {
222       auto __i_(valobj_sp->GetChildMemberWithName(g___i_, true));
223       if (!__i_) {
224         m_pair_ptr = nullptr;
225         return false;
226       }
227       CompilerType pair_type(
228           __i_->GetCompilerType().GetTypeTemplateArgument(0));
229       std::string name;
230       uint64_t bit_offset_ptr;
231       uint32_t bitfield_bit_size_ptr;
232       bool is_bitfield_ptr;
233       pair_type = pair_type.GetFieldAtIndex(
234           0, name, &bit_offset_ptr, &bitfield_bit_size_ptr, &is_bitfield_ptr);
235       if (!pair_type) {
236         m_pair_ptr = nullptr;
237         return false;
238       }
239 
240       auto addr(m_pair_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS));
241       m_pair_ptr = nullptr;
242       if (addr && addr != LLDB_INVALID_ADDRESS) {
243         TypeSystemClang *ast_ctx =
244             llvm::dyn_cast_or_null<TypeSystemClang>(pair_type.GetTypeSystem());
245         if (!ast_ctx)
246           return false;
247         CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(
248             ConstString(),
249             {{"ptr0",
250               ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
251              {"ptr1",
252               ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
253              {"ptr2",
254               ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
255              {"cw", ast_ctx->GetBasicType(lldb::eBasicTypeBool)},
256              {"payload", pair_type}});
257         llvm::Optional<uint64_t> size = tree_node_type.GetByteSize(nullptr);
258         if (!size)
259           return false;
260         DataBufferSP buffer_sp(new DataBufferHeap(*size, 0));
261         ProcessSP process_sp(target_sp->GetProcessSP());
262         Status error;
263         process_sp->ReadMemory(addr, buffer_sp->GetBytes(),
264                                buffer_sp->GetByteSize(), error);
265         if (error.Fail())
266           return false;
267         DataExtractor extractor(buffer_sp, process_sp->GetByteOrder(),
268                                 process_sp->GetAddressByteSize());
269         auto pair_sp = CreateValueObjectFromData(
270             "pair", extractor, valobj_sp->GetExecutionContextRef(),
271             tree_node_type);
272         if (pair_sp)
273           m_pair_sp = pair_sp->GetChildAtIndex(4, true);
274       }
275     }
276   }
277 
278   return false;
279 }
280 
281 size_t lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
282     CalculateNumChildren() {
283   return 2;
284 }
285 
286 lldb::ValueObjectSP
287 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::GetChildAtIndex(
288     size_t idx) {
289   if (m_pair_ptr)
290     return m_pair_ptr->GetChildAtIndex(idx, true);
291   if (m_pair_sp)
292     return m_pair_sp->GetChildAtIndex(idx, true);
293   return lldb::ValueObjectSP();
294 }
295 
296 bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
297     MightHaveChildren() {
298   return true;
299 }
300 
301 size_t lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
302     GetIndexOfChildWithName(ConstString name) {
303   if (name == "first")
304     return 0;
305   if (name == "second")
306     return 1;
307   return UINT32_MAX;
308 }
309 
310 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::
311     ~LibCxxMapIteratorSyntheticFrontEnd() {
312   // this will be deleted when its parent dies (since it's a child object)
313   // delete m_pair_ptr;
314 }
315 
316 SyntheticChildrenFrontEnd *
317 lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEndCreator(
318     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
319   return (valobj_sp ? new LibCxxMapIteratorSyntheticFrontEnd(valobj_sp)
320                     : nullptr);
321 }
322 
323 /*
324  (lldb) fr var ibeg --raw --ptr-depth 1 -T
325  (std::__1::__wrap_iter<int *>) ibeg = {
326  (std::__1::__wrap_iter<int *>::iterator_type) __i = 0x00000001001037a0 {
327  (int) *__i = 1
328  }
329  }
330 */
331 
332 SyntheticChildrenFrontEnd *
333 lldb_private::formatters::LibCxxVectorIteratorSyntheticFrontEndCreator(
334     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
335   static ConstString g_item_name;
336   if (!g_item_name)
337     g_item_name.SetCString("__i");
338   return (valobj_sp
339               ? new VectorIteratorSyntheticFrontEnd(valobj_sp, g_item_name)
340               : nullptr);
341 }
342 
343 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
344     LibcxxSharedPtrSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
345     : SyntheticChildrenFrontEnd(*valobj_sp), m_cntrl(nullptr), m_count_sp(),
346       m_weak_count_sp(), m_ptr_size(0), m_byte_order(lldb::eByteOrderInvalid) {
347   if (valobj_sp)
348     Update();
349 }
350 
351 size_t lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
352     CalculateNumChildren() {
353   return (m_cntrl ? 1 : 0);
354 }
355 
356 lldb::ValueObjectSP
357 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::GetChildAtIndex(
358     size_t idx) {
359   if (!m_cntrl)
360     return lldb::ValueObjectSP();
361 
362   ValueObjectSP valobj_sp = m_backend.GetSP();
363   if (!valobj_sp)
364     return lldb::ValueObjectSP();
365 
366   if (idx == 0)
367     return valobj_sp->GetChildMemberWithName(ConstString("__ptr_"), true);
368 
369   if (idx > 2)
370     return lldb::ValueObjectSP();
371 
372   if (idx == 1) {
373     if (!m_count_sp) {
374       ValueObjectSP shared_owners_sp(m_cntrl->GetChildMemberWithName(
375           ConstString("__shared_owners_"), true));
376       if (!shared_owners_sp)
377         return lldb::ValueObjectSP();
378       uint64_t count = 1 + shared_owners_sp->GetValueAsUnsigned(0);
379       DataExtractor data(&count, 8, m_byte_order, m_ptr_size);
380       m_count_sp = CreateValueObjectFromData(
381           "count", data, valobj_sp->GetExecutionContextRef(),
382           shared_owners_sp->GetCompilerType());
383     }
384     return m_count_sp;
385   } else /* if (idx == 2) */
386   {
387     if (!m_weak_count_sp) {
388       ValueObjectSP shared_weak_owners_sp(m_cntrl->GetChildMemberWithName(
389           ConstString("__shared_weak_owners_"), true));
390       if (!shared_weak_owners_sp)
391         return lldb::ValueObjectSP();
392       uint64_t count = 1 + shared_weak_owners_sp->GetValueAsUnsigned(0);
393       DataExtractor data(&count, 8, m_byte_order, m_ptr_size);
394       m_weak_count_sp = CreateValueObjectFromData(
395           "count", data, valobj_sp->GetExecutionContextRef(),
396           shared_weak_owners_sp->GetCompilerType());
397     }
398     return m_weak_count_sp;
399   }
400 }
401 
402 bool lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::Update() {
403   m_count_sp.reset();
404   m_weak_count_sp.reset();
405   m_cntrl = nullptr;
406 
407   ValueObjectSP valobj_sp = m_backend.GetSP();
408   if (!valobj_sp)
409     return false;
410 
411   TargetSP target_sp(valobj_sp->GetTargetSP());
412   if (!target_sp)
413     return false;
414 
415   m_byte_order = target_sp->GetArchitecture().GetByteOrder();
416   m_ptr_size = target_sp->GetArchitecture().GetAddressByteSize();
417 
418   lldb::ValueObjectSP cntrl_sp(
419       valobj_sp->GetChildMemberWithName(ConstString("__cntrl_"), true));
420 
421   m_cntrl = cntrl_sp.get(); // need to store the raw pointer to avoid a circular
422                             // dependency
423   return false;
424 }
425 
426 bool lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
427     MightHaveChildren() {
428   return true;
429 }
430 
431 size_t lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
432     GetIndexOfChildWithName(ConstString name) {
433   if (name == "__ptr_")
434     return 0;
435   if (name == "count")
436     return 1;
437   if (name == "weak_count")
438     return 2;
439   return UINT32_MAX;
440 }
441 
442 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEnd::
443     ~LibcxxSharedPtrSyntheticFrontEnd() = default;
444 
445 SyntheticChildrenFrontEnd *
446 lldb_private::formatters::LibcxxSharedPtrSyntheticFrontEndCreator(
447     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
448   return (valobj_sp ? new LibcxxSharedPtrSyntheticFrontEnd(valobj_sp)
449                     : nullptr);
450 }
451 
452 bool lldb_private::formatters::LibcxxContainerSummaryProvider(
453     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
454   if (valobj.IsPointerType()) {
455     uint64_t value = valobj.GetValueAsUnsigned(0);
456     if (!value)
457       return false;
458     stream.Printf("0x%016" PRIx64 " ", value);
459   }
460   return FormatEntity::FormatStringRef("size=${svar%#}", stream, nullptr,
461                                        nullptr, nullptr, &valobj, false, false);
462 }
463 
464 // the field layout in a libc++ string (cap, side, data or data, size, cap)
465 enum LibcxxStringLayoutMode {
466   eLibcxxStringLayoutModeCSD = 0,
467   eLibcxxStringLayoutModeDSC = 1,
468   eLibcxxStringLayoutModeInvalid = 0xffff
469 };
470 
471 /// Determine the size in bytes of \p valobj (a libc++ std::string object) and
472 /// extract its data payload. Return the size + payload pair.
473 static llvm::Optional<std::pair<uint64_t, ValueObjectSP>>
474 ExtractLibcxxStringInfo(ValueObject &valobj) {
475   ValueObjectSP D(valobj.GetChildAtIndexPath({0, 0, 0, 0}));
476   if (!D)
477     return {};
478 
479   ValueObjectSP layout_decider(
480     D->GetChildAtIndexPath(llvm::ArrayRef<size_t>({0, 0})));
481 
482   // this child should exist
483   if (!layout_decider)
484     return {};
485 
486   ConstString g_data_name("__data_");
487   ConstString g_size_name("__size_");
488   bool short_mode = false; // this means the string is in short-mode and the
489                            // data is stored inline
490   LibcxxStringLayoutMode layout = (layout_decider->GetName() == g_data_name)
491                                       ? eLibcxxStringLayoutModeDSC
492                                       : eLibcxxStringLayoutModeCSD;
493   uint64_t size_mode_value = 0;
494 
495   if (layout == eLibcxxStringLayoutModeDSC) {
496     ValueObjectSP size_mode(D->GetChildAtIndexPath({1, 1, 0}));
497     if (!size_mode)
498       return {};
499 
500     if (size_mode->GetName() != g_size_name) {
501       // we are hitting the padding structure, move along
502       size_mode = D->GetChildAtIndexPath({1, 1, 1});
503       if (!size_mode)
504         return {};
505     }
506 
507     size_mode_value = (size_mode->GetValueAsUnsigned(0));
508     short_mode = ((size_mode_value & 0x80) == 0);
509   } else {
510     ValueObjectSP size_mode(D->GetChildAtIndexPath({1, 0, 0}));
511     if (!size_mode)
512       return {};
513 
514     size_mode_value = (size_mode->GetValueAsUnsigned(0));
515     short_mode = ((size_mode_value & 1) == 0);
516   }
517 
518   if (short_mode) {
519     ValueObjectSP s(D->GetChildAtIndex(1, true));
520     if (!s)
521       return {};
522     ValueObjectSP location_sp = s->GetChildAtIndex(
523         (layout == eLibcxxStringLayoutModeDSC) ? 0 : 1, true);
524     const uint64_t size = (layout == eLibcxxStringLayoutModeDSC)
525                               ? size_mode_value
526                               : ((size_mode_value >> 1) % 256);
527 
528     // When the small-string optimization takes place, the data must fit in the
529     // inline string buffer (23 bytes on x86_64/Darwin). If it doesn't, it's
530     // likely that the string isn't initialized and we're reading garbage.
531     ExecutionContext exe_ctx(location_sp->GetExecutionContextRef());
532     const llvm::Optional<uint64_t> max_bytes =
533         location_sp->GetCompilerType().GetByteSize(
534             exe_ctx.GetBestExecutionContextScope());
535     if (!max_bytes || size > *max_bytes || !location_sp)
536       return {};
537 
538     return std::make_pair(size, location_sp);
539   }
540 
541   ValueObjectSP l(D->GetChildAtIndex(0, true));
542   if (!l)
543     return {};
544   // we can use the layout_decider object as the data pointer
545   ValueObjectSP location_sp = (layout == eLibcxxStringLayoutModeDSC)
546                                   ? layout_decider
547                                   : l->GetChildAtIndex(2, true);
548   ValueObjectSP size_vo(l->GetChildAtIndex(1, true));
549   const unsigned capacity_index =
550       (layout == eLibcxxStringLayoutModeDSC) ? 2 : 0;
551   ValueObjectSP capacity_vo(l->GetChildAtIndex(capacity_index, true));
552   if (!size_vo || !location_sp || !capacity_vo)
553     return {};
554   const uint64_t size = size_vo->GetValueAsUnsigned(LLDB_INVALID_OFFSET);
555   const uint64_t capacity =
556       capacity_vo->GetValueAsUnsigned(LLDB_INVALID_OFFSET);
557   if (size == LLDB_INVALID_OFFSET || capacity == LLDB_INVALID_OFFSET ||
558       capacity < size)
559     return {};
560   return std::make_pair(size, location_sp);
561 }
562 
563 bool lldb_private::formatters::LibcxxWStringSummaryProvider(
564     ValueObject &valobj, Stream &stream,
565     const TypeSummaryOptions &summary_options) {
566   auto string_info = ExtractLibcxxStringInfo(valobj);
567   if (!string_info)
568     return false;
569   uint64_t size;
570   ValueObjectSP location_sp;
571   std::tie(size, location_sp) = *string_info;
572 
573   if (size == 0) {
574     stream.Printf("L\"\"");
575     return true;
576   }
577   if (!location_sp)
578     return false;
579 
580 
581   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
582   if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
583     const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
584     if (size > max_size) {
585       size = max_size;
586       options.SetIsTruncated(true);
587     }
588   }
589 
590   DataExtractor extractor;
591   const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
592   if (bytes_read < size)
593     return false;
594 
595   // std::wstring::size() is measured in 'characters', not bytes
596   TypeSystemClang *ast_context =
597       TypeSystemClang::GetScratch(*valobj.GetTargetSP());
598   if (!ast_context)
599     return false;
600 
601   auto wchar_t_size =
602       ast_context->GetBasicType(lldb::eBasicTypeWChar).GetByteSize(nullptr);
603   if (!wchar_t_size)
604     return false;
605 
606   options.SetData(extractor);
607   options.SetStream(&stream);
608   options.SetPrefixToken("L");
609   options.SetQuote('"');
610   options.SetSourceSize(size);
611   options.SetBinaryZeroIsTerminator(false);
612 
613   switch (*wchar_t_size) {
614   case 1:
615     return StringPrinter::ReadBufferAndDumpToStream<
616         lldb_private::formatters::StringPrinter::StringElementType::UTF8>(
617         options);
618     break;
619 
620   case 2:
621     return StringPrinter::ReadBufferAndDumpToStream<
622         lldb_private::formatters::StringPrinter::StringElementType::UTF16>(
623         options);
624     break;
625 
626   case 4:
627     return StringPrinter::ReadBufferAndDumpToStream<
628         lldb_private::formatters::StringPrinter::StringElementType::UTF32>(
629         options);
630   }
631   return false;
632 }
633 
634 template <StringPrinter::StringElementType element_type>
635 bool LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
636                                  const TypeSummaryOptions &summary_options,
637                                  std::string prefix_token) {
638   auto string_info = ExtractLibcxxStringInfo(valobj);
639   if (!string_info)
640     return false;
641   uint64_t size;
642   ValueObjectSP location_sp;
643   std::tie(size, location_sp) = *string_info;
644 
645   if (size == 0) {
646     stream.Printf("\"\"");
647     return true;
648   }
649 
650   if (!location_sp)
651     return false;
652 
653   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
654 
655   if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
656     const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
657     if (size > max_size) {
658       size = max_size;
659       options.SetIsTruncated(true);
660     }
661   }
662 
663   DataExtractor extractor;
664   const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
665   if (bytes_read < size)
666     return false;
667 
668   options.SetData(extractor);
669   options.SetStream(&stream);
670   if (prefix_token.empty())
671     options.SetPrefixToken(nullptr);
672   else
673     options.SetPrefixToken(prefix_token);
674   options.SetQuote('"');
675   options.SetSourceSize(size);
676   options.SetBinaryZeroIsTerminator(false);
677   return StringPrinter::ReadBufferAndDumpToStream<element_type>(options);
678 }
679 
680 template <StringPrinter::StringElementType element_type>
681 static bool formatStringImpl(ValueObject &valobj, Stream &stream,
682                              const TypeSummaryOptions &summary_options,
683                              std::string prefix_token) {
684   StreamString scratch_stream;
685   const bool success = LibcxxStringSummaryProvider<element_type>(
686       valobj, scratch_stream, summary_options, prefix_token);
687   if (success)
688     stream << scratch_stream.GetData();
689   else
690     stream << "Summary Unavailable";
691   return true;
692 }
693 
694 bool lldb_private::formatters::LibcxxStringSummaryProviderASCII(
695     ValueObject &valobj, Stream &stream,
696     const TypeSummaryOptions &summary_options) {
697   return formatStringImpl<StringPrinter::StringElementType::ASCII>(
698       valobj, stream, summary_options, "");
699 }
700 
701 bool lldb_private::formatters::LibcxxStringSummaryProviderUTF16(
702     ValueObject &valobj, Stream &stream,
703     const TypeSummaryOptions &summary_options) {
704   return formatStringImpl<StringPrinter::StringElementType::UTF16>(
705       valobj, stream, summary_options, "u");
706 }
707 
708 bool lldb_private::formatters::LibcxxStringSummaryProviderUTF32(
709     ValueObject &valobj, Stream &stream,
710     const TypeSummaryOptions &summary_options) {
711   return formatStringImpl<StringPrinter::StringElementType::UTF32>(
712       valobj, stream, summary_options, "U");
713 }
714