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 namespace {
551 enum class StringLayout { CSD, DSC };
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 // TODO: Support big-endian architectures.
557 static llvm::Optional<std::pair<uint64_t, ValueObjectSP>>
558 ExtractLibcxxStringInfo(ValueObject &valobj) {
559   ValueObjectSP valobj_r_sp =
560       valobj.GetChildMemberWithName(ConstString("__r_"), /*can_create=*/true);
561   if (!valobj_r_sp)
562     return {};
563 
564   // __r_ is a compressed_pair of the actual data and the allocator. The data we
565   // want is in the first base class.
566   ValueObjectSP valobj_r_base_sp =
567       valobj_r_sp->GetChildAtIndex(0, /*can_create=*/true);
568   if (!valobj_r_base_sp)
569     return {};
570 
571   ValueObjectSP valobj_rep_sp = valobj_r_base_sp->GetChildMemberWithName(
572       ConstString("__value_"), /*can_create=*/true);
573   if (!valobj_rep_sp)
574     return {};
575 
576   ValueObjectSP l = valobj_rep_sp->GetChildMemberWithName(ConstString("__l"),
577                                                           /*can_create=*/true);
578   if (!l)
579     return {};
580 
581   StringLayout layout = l->GetIndexOfChildWithName(ConstString("__data_")) == 0
582                             ? StringLayout::DSC
583                             : StringLayout::CSD;
584 
585   bool short_mode = false; // this means the string is in short-mode and the
586                            // data is stored inline
587   bool using_bitmasks = true; // Whether the class uses bitmasks for the mode
588                               // flag (pre-D123580).
589   uint64_t size;
590   uint64_t size_mode_value = 0;
591 
592   ValueObjectSP short_sp = valobj_rep_sp->GetChildMemberWithName(
593       ConstString("__s"), /*can_create=*/true);
594   if (!short_sp)
595     return {};
596 
597   ValueObjectSP is_long =
598       short_sp->GetChildMemberWithName(ConstString("__is_long_"), true);
599   ValueObjectSP size_sp =
600       short_sp->GetChildAtNamePath({ConstString("__size_")});
601   if (!size_sp)
602     return {};
603 
604   if (is_long) {
605     using_bitmasks = false;
606     short_mode = !is_long->GetValueAsUnsigned(/*fail_value=*/0);
607     size = size_sp->GetValueAsUnsigned(/*fail_value=*/0);
608   } else {
609     // The string mode is encoded in the size field.
610     size_mode_value = size_sp->GetValueAsUnsigned(0);
611     uint8_t mode_mask = layout == StringLayout::DSC ? 0x80 : 1;
612     short_mode = (size_mode_value & mode_mask) == 0;
613   }
614 
615   if (short_mode) {
616     ValueObjectSP location_sp =
617         short_sp->GetChildMemberWithName(ConstString("__data_"), true);
618     if (using_bitmasks)
619       size = (layout == StringLayout::DSC) ? size_mode_value
620                                            : ((size_mode_value >> 1) % 256);
621 
622     // When the small-string optimization takes place, the data must fit in the
623     // inline string buffer (23 bytes on x86_64/Darwin). If it doesn't, it's
624     // likely that the string isn't initialized and we're reading garbage.
625     ExecutionContext exe_ctx(location_sp->GetExecutionContextRef());
626     const llvm::Optional<uint64_t> max_bytes =
627         location_sp->GetCompilerType().GetByteSize(
628             exe_ctx.GetBestExecutionContextScope());
629     if (!max_bytes || size > *max_bytes || !location_sp)
630       return {};
631 
632     return std::make_pair(size, location_sp);
633   }
634 
635   // we can use the layout_decider object as the data pointer
636   ValueObjectSP location_sp =
637       l->GetChildMemberWithName(ConstString("__data_"), /*can_create=*/true);
638   ValueObjectSP size_vo =
639       l->GetChildMemberWithName(ConstString("__size_"), /*can_create=*/true);
640   ValueObjectSP capacity_vo =
641       l->GetChildMemberWithName(ConstString("__cap_"), /*can_create=*/true);
642   if (!size_vo || !location_sp || !capacity_vo)
643     return {};
644   size = size_vo->GetValueAsUnsigned(LLDB_INVALID_OFFSET);
645   uint64_t capacity = capacity_vo->GetValueAsUnsigned(LLDB_INVALID_OFFSET);
646   if (!using_bitmasks && layout == StringLayout::CSD)
647     capacity *= 2;
648   if (size == LLDB_INVALID_OFFSET || capacity == LLDB_INVALID_OFFSET ||
649       capacity < size)
650     return {};
651   return std::make_pair(size, location_sp);
652 }
653 
654 static bool
655 LibcxxWStringSummaryProvider(ValueObject &valobj, Stream &stream,
656                              const TypeSummaryOptions &summary_options,
657                              ValueObjectSP location_sp, size_t size) {
658   if (size == 0) {
659     stream.Printf("L\"\"");
660     return true;
661   }
662   if (!location_sp)
663     return false;
664 
665   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
666   if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
667     const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
668     if (size > max_size) {
669       size = max_size;
670       options.SetIsTruncated(true);
671     }
672   }
673 
674   DataExtractor extractor;
675   const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
676   if (bytes_read < size)
677     return false;
678 
679   // std::wstring::size() is measured in 'characters', not bytes
680   TypeSystemClang *ast_context =
681       ScratchTypeSystemClang::GetForTarget(*valobj.GetTargetSP());
682   if (!ast_context)
683     return false;
684 
685   auto wchar_t_size =
686       ast_context->GetBasicType(lldb::eBasicTypeWChar).GetByteSize(nullptr);
687   if (!wchar_t_size)
688     return false;
689 
690   options.SetData(std::move(extractor));
691   options.SetStream(&stream);
692   options.SetPrefixToken("L");
693   options.SetQuote('"');
694   options.SetSourceSize(size);
695   options.SetBinaryZeroIsTerminator(false);
696 
697   switch (*wchar_t_size) {
698   case 1:
699     return StringPrinter::ReadBufferAndDumpToStream<
700         lldb_private::formatters::StringPrinter::StringElementType::UTF8>(
701         options);
702     break;
703 
704   case 2:
705     return StringPrinter::ReadBufferAndDumpToStream<
706         lldb_private::formatters::StringPrinter::StringElementType::UTF16>(
707         options);
708     break;
709 
710   case 4:
711     return StringPrinter::ReadBufferAndDumpToStream<
712         lldb_private::formatters::StringPrinter::StringElementType::UTF32>(
713         options);
714   }
715   return false;
716 }
717 
718 bool lldb_private::formatters::LibcxxWStringSummaryProvider(
719     ValueObject &valobj, Stream &stream,
720     const TypeSummaryOptions &summary_options) {
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   return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
729                                         location_sp, size);
730 }
731 
732 template <StringPrinter::StringElementType element_type>
733 static bool
734 LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
735                             const TypeSummaryOptions &summary_options,
736                             std::string prefix_token, ValueObjectSP location_sp,
737                             uint64_t size) {
738 
739   if (size == 0) {
740     stream.Printf("\"\"");
741     return true;
742   }
743 
744   if (!location_sp)
745     return false;
746 
747   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
748 
749   if (summary_options.GetCapping() == TypeSummaryCapping::eTypeSummaryCapped) {
750     const auto max_size = valobj.GetTargetSP()->GetMaximumSizeOfStringSummary();
751     if (size > max_size) {
752       size = max_size;
753       options.SetIsTruncated(true);
754     }
755   }
756 
757   {
758     DataExtractor extractor;
759     const size_t bytes_read = location_sp->GetPointeeData(extractor, 0, size);
760     if (bytes_read < size)
761       return false;
762 
763     options.SetData(std::move(extractor));
764   }
765   options.SetStream(&stream);
766   if (prefix_token.empty())
767     options.SetPrefixToken(nullptr);
768   else
769     options.SetPrefixToken(prefix_token);
770   options.SetQuote('"');
771   options.SetSourceSize(size);
772   options.SetBinaryZeroIsTerminator(false);
773   return StringPrinter::ReadBufferAndDumpToStream<element_type>(options);
774 }
775 
776 template <StringPrinter::StringElementType element_type>
777 static bool
778 LibcxxStringSummaryProvider(ValueObject &valobj, Stream &stream,
779                             const TypeSummaryOptions &summary_options,
780                             std::string prefix_token) {
781   auto string_info = ExtractLibcxxStringInfo(valobj);
782   if (!string_info)
783     return false;
784   uint64_t size;
785   ValueObjectSP location_sp;
786   std::tie(size, location_sp) = *string_info;
787 
788   return LibcxxStringSummaryProvider<element_type>(
789       valobj, stream, summary_options, prefix_token, location_sp, size);
790 }
791 template <StringPrinter::StringElementType element_type>
792 static bool formatStringImpl(ValueObject &valobj, Stream &stream,
793                              const TypeSummaryOptions &summary_options,
794                              std::string prefix_token) {
795   StreamString scratch_stream;
796   const bool success = LibcxxStringSummaryProvider<element_type>(
797       valobj, scratch_stream, summary_options, prefix_token);
798   if (success)
799     stream << scratch_stream.GetData();
800   else
801     stream << "Summary Unavailable";
802   return true;
803 }
804 
805 bool lldb_private::formatters::LibcxxStringSummaryProviderASCII(
806     ValueObject &valobj, Stream &stream,
807     const TypeSummaryOptions &summary_options) {
808   return formatStringImpl<StringPrinter::StringElementType::ASCII>(
809       valobj, stream, summary_options, "");
810 }
811 
812 bool lldb_private::formatters::LibcxxStringSummaryProviderUTF16(
813     ValueObject &valobj, Stream &stream,
814     const TypeSummaryOptions &summary_options) {
815   return formatStringImpl<StringPrinter::StringElementType::UTF16>(
816       valobj, stream, summary_options, "u");
817 }
818 
819 bool lldb_private::formatters::LibcxxStringSummaryProviderUTF32(
820     ValueObject &valobj, Stream &stream,
821     const TypeSummaryOptions &summary_options) {
822   return formatStringImpl<StringPrinter::StringElementType::UTF32>(
823       valobj, stream, summary_options, "U");
824 }
825 
826 static std::tuple<bool, ValueObjectSP, size_t>
827 LibcxxExtractStringViewData(ValueObject& valobj) {
828   ConstString g_data_name("__data");
829   ConstString g_size_name("__size");
830   auto dataobj = valobj.GetChildMemberWithName(g_data_name, true);
831   auto sizeobj = valobj.GetChildMemberWithName(g_size_name, true);
832 
833   if (!dataobj || !sizeobj)
834     return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
835 
836   if (!dataobj->GetError().Success() || !sizeobj->GetError().Success())
837     return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
838 
839   bool success{false};
840   uint64_t size = sizeobj->GetValueAsUnsigned(0, &success);
841   if (!success)
842     return std::make_tuple<bool,ValueObjectSP,size_t>(false, {}, {});
843 
844   return std::make_tuple(true,dataobj,size);
845 }
846 
847 template <StringPrinter::StringElementType element_type>
848 static bool formatStringViewImpl(ValueObject &valobj, Stream &stream,
849                                  const TypeSummaryOptions &summary_options,
850                                  std::string prefix_token) {
851 
852   bool success;
853   ValueObjectSP dataobj;
854   size_t size;
855   std::tie(success, dataobj, size) = LibcxxExtractStringViewData(valobj);
856 
857   if (!success) {
858     stream << "Summary Unavailable";
859     return true;
860   }
861 
862   return LibcxxStringSummaryProvider<element_type>(
863       valobj, stream, summary_options, prefix_token, dataobj, size);
864 }
865 
866 bool lldb_private::formatters::LibcxxStringViewSummaryProviderASCII(
867     ValueObject &valobj, Stream &stream,
868     const TypeSummaryOptions &summary_options) {
869   return formatStringViewImpl<StringPrinter::StringElementType::ASCII>(
870       valobj, stream, summary_options, "");
871 }
872 
873 bool lldb_private::formatters::LibcxxStringViewSummaryProviderUTF16(
874     ValueObject &valobj, Stream &stream,
875     const TypeSummaryOptions &summary_options) {
876   return formatStringViewImpl<StringPrinter::StringElementType::UTF16>(
877       valobj, stream, summary_options, "u");
878 }
879 
880 bool lldb_private::formatters::LibcxxStringViewSummaryProviderUTF32(
881     ValueObject &valobj, Stream &stream,
882     const TypeSummaryOptions &summary_options) {
883   return formatStringViewImpl<StringPrinter::StringElementType::UTF32>(
884       valobj, stream, summary_options, "U");
885 }
886 
887 bool lldb_private::formatters::LibcxxWStringViewSummaryProvider(
888     ValueObject &valobj, Stream &stream,
889     const TypeSummaryOptions &summary_options) {
890 
891   bool success;
892   ValueObjectSP dataobj;
893   size_t size;
894   std::tie( success, dataobj, size ) = LibcxxExtractStringViewData(valobj);
895 
896   if (!success) {
897     stream << "Summary Unavailable";
898     return true;
899   }
900 
901 
902   return ::LibcxxWStringSummaryProvider(valobj, stream, summary_options,
903                                         dataobj, size);
904 }
905