1 //===-- Symbol.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 "lldb/Symbol/Symbol.h"
10 
11 #include "lldb/Core/Module.h"
12 #include "lldb/Core/ModuleSpec.h"
13 #include "lldb/Core/Section.h"
14 #include "lldb/Symbol/Function.h"
15 #include "lldb/Symbol/ObjectFile.h"
16 #include "lldb/Symbol/SymbolVendor.h"
17 #include "lldb/Symbol/Symtab.h"
18 #include "lldb/Target/Process.h"
19 #include "lldb/Target/Target.h"
20 #include "lldb/Utility/Stream.h"
21 
22 using namespace lldb;
23 using namespace lldb_private;
24 
25 Symbol::Symbol()
26     : SymbolContextScope(), m_type_data_resolved(false), m_is_synthetic(false),
27       m_is_debug(false), m_is_external(false), m_size_is_sibling(false),
28       m_size_is_synthesized(false), m_size_is_valid(false),
29       m_demangled_is_synthesized(false), m_contains_linker_annotations(false),
30       m_is_weak(false), m_type(eSymbolTypeInvalid), m_mangled(),
31       m_addr_range() {}
32 
33 Symbol::Symbol(uint32_t symID, llvm::StringRef name, SymbolType type, bool external,
34                bool is_debug, bool is_trampoline, bool is_artificial,
35                const lldb::SectionSP &section_sp, addr_t offset, addr_t size,
36                bool size_is_valid, bool contains_linker_annotations,
37                uint32_t flags)
38     : SymbolContextScope(), m_uid(symID), m_type_data(0),
39       m_type_data_resolved(false), m_is_synthetic(is_artificial),
40       m_is_debug(is_debug), m_is_external(external), m_size_is_sibling(false),
41       m_size_is_synthesized(false), m_size_is_valid(size_is_valid || size > 0),
42       m_demangled_is_synthesized(false),
43       m_contains_linker_annotations(contains_linker_annotations),
44       m_is_weak(false), m_type(type),
45       m_mangled(name),
46       m_addr_range(section_sp, offset, size), m_flags(flags) {}
47 
48 Symbol::Symbol(uint32_t symID, const Mangled &mangled, SymbolType type,
49                bool external, bool is_debug, bool is_trampoline,
50                bool is_artificial, const AddressRange &range,
51                bool size_is_valid, bool contains_linker_annotations,
52                uint32_t flags)
53     : SymbolContextScope(), m_uid(symID), m_type_data(0),
54       m_type_data_resolved(false), m_is_synthetic(is_artificial),
55       m_is_debug(is_debug), m_is_external(external), m_size_is_sibling(false),
56       m_size_is_synthesized(false),
57       m_size_is_valid(size_is_valid || range.GetByteSize() > 0),
58       m_demangled_is_synthesized(false),
59       m_contains_linker_annotations(contains_linker_annotations),
60       m_is_weak(false), m_type(type), m_mangled(mangled), m_addr_range(range),
61       m_flags(flags) {}
62 
63 Symbol::Symbol(const Symbol &rhs)
64     : SymbolContextScope(rhs), m_uid(rhs.m_uid), m_type_data(rhs.m_type_data),
65       m_type_data_resolved(rhs.m_type_data_resolved),
66       m_is_synthetic(rhs.m_is_synthetic), m_is_debug(rhs.m_is_debug),
67       m_is_external(rhs.m_is_external),
68       m_size_is_sibling(rhs.m_size_is_sibling), m_size_is_synthesized(false),
69       m_size_is_valid(rhs.m_size_is_valid),
70       m_demangled_is_synthesized(rhs.m_demangled_is_synthesized),
71       m_contains_linker_annotations(rhs.m_contains_linker_annotations),
72       m_is_weak(rhs.m_is_weak), m_type(rhs.m_type), m_mangled(rhs.m_mangled),
73       m_addr_range(rhs.m_addr_range), m_flags(rhs.m_flags) {}
74 
75 const Symbol &Symbol::operator=(const Symbol &rhs) {
76   if (this != &rhs) {
77     SymbolContextScope::operator=(rhs);
78     m_uid = rhs.m_uid;
79     m_type_data = rhs.m_type_data;
80     m_type_data_resolved = rhs.m_type_data_resolved;
81     m_is_synthetic = rhs.m_is_synthetic;
82     m_is_debug = rhs.m_is_debug;
83     m_is_external = rhs.m_is_external;
84     m_size_is_sibling = rhs.m_size_is_sibling;
85     m_size_is_synthesized = rhs.m_size_is_sibling;
86     m_size_is_valid = rhs.m_size_is_valid;
87     m_demangled_is_synthesized = rhs.m_demangled_is_synthesized;
88     m_contains_linker_annotations = rhs.m_contains_linker_annotations;
89     m_is_weak = rhs.m_is_weak;
90     m_type = rhs.m_type;
91     m_mangled = rhs.m_mangled;
92     m_addr_range = rhs.m_addr_range;
93     m_flags = rhs.m_flags;
94   }
95   return *this;
96 }
97 
98 void Symbol::Clear() {
99   m_uid = UINT32_MAX;
100   m_mangled.Clear();
101   m_type_data = 0;
102   m_type_data_resolved = false;
103   m_is_synthetic = false;
104   m_is_debug = false;
105   m_is_external = false;
106   m_size_is_sibling = false;
107   m_size_is_synthesized = false;
108   m_size_is_valid = false;
109   m_demangled_is_synthesized = false;
110   m_contains_linker_annotations = false;
111   m_is_weak = false;
112   m_type = eSymbolTypeInvalid;
113   m_flags = 0;
114   m_addr_range.Clear();
115 }
116 
117 bool Symbol::ValueIsAddress() const {
118   return m_addr_range.GetBaseAddress().GetSection().get() != nullptr;
119 }
120 
121 ConstString Symbol::GetDisplayName() const {
122   return GetMangled().GetDisplayDemangledName();
123 }
124 
125 ConstString Symbol::GetReExportedSymbolName() const {
126   if (m_type == eSymbolTypeReExported) {
127     // For eSymbolTypeReExported, the "const char *" from a ConstString is used
128     // as the offset in the address range base address. We can then make this
129     // back into a string that is the re-exported name.
130     intptr_t str_ptr = m_addr_range.GetBaseAddress().GetOffset();
131     if (str_ptr != 0)
132       return ConstString((const char *)str_ptr);
133     else
134       return GetName();
135   }
136   return ConstString();
137 }
138 
139 FileSpec Symbol::GetReExportedSymbolSharedLibrary() const {
140   if (m_type == eSymbolTypeReExported) {
141     // For eSymbolTypeReExported, the "const char *" from a ConstString is used
142     // as the offset in the address range base address. We can then make this
143     // back into a string that is the re-exported name.
144     intptr_t str_ptr = m_addr_range.GetByteSize();
145     if (str_ptr != 0)
146       return FileSpec((const char *)str_ptr);
147   }
148   return FileSpec();
149 }
150 
151 void Symbol::SetReExportedSymbolName(ConstString name) {
152   SetType(eSymbolTypeReExported);
153   // For eSymbolTypeReExported, the "const char *" from a ConstString is used
154   // as the offset in the address range base address.
155   m_addr_range.GetBaseAddress().SetOffset((uintptr_t)name.GetCString());
156 }
157 
158 bool Symbol::SetReExportedSymbolSharedLibrary(const FileSpec &fspec) {
159   if (m_type == eSymbolTypeReExported) {
160     // For eSymbolTypeReExported, the "const char *" from a ConstString is used
161     // as the offset in the address range base address.
162     m_addr_range.SetByteSize(
163         (uintptr_t)ConstString(fspec.GetPath().c_str()).GetCString());
164     return true;
165   }
166   return false;
167 }
168 
169 uint32_t Symbol::GetSiblingIndex() const {
170   return m_size_is_sibling ? m_addr_range.GetByteSize() : UINT32_MAX;
171 }
172 
173 bool Symbol::IsTrampoline() const { return m_type == eSymbolTypeTrampoline; }
174 
175 bool Symbol::IsIndirect() const { return m_type == eSymbolTypeResolver; }
176 
177 void Symbol::GetDescription(Stream *s, lldb::DescriptionLevel level,
178                             Target *target) const {
179   s->Printf("id = {0x%8.8x}", m_uid);
180 
181   if (m_addr_range.GetBaseAddress().GetSection()) {
182     if (ValueIsAddress()) {
183       const lldb::addr_t byte_size = GetByteSize();
184       if (byte_size > 0) {
185         s->PutCString(", range = ");
186         m_addr_range.Dump(s, target, Address::DumpStyleLoadAddress,
187                           Address::DumpStyleFileAddress);
188       } else {
189         s->PutCString(", address = ");
190         m_addr_range.GetBaseAddress().Dump(s, target,
191                                            Address::DumpStyleLoadAddress,
192                                            Address::DumpStyleFileAddress);
193       }
194     } else
195       s->Printf(", value = 0x%16.16" PRIx64,
196                 m_addr_range.GetBaseAddress().GetOffset());
197   } else {
198     if (m_size_is_sibling)
199       s->Printf(", sibling = %5" PRIu64,
200                 m_addr_range.GetBaseAddress().GetOffset());
201     else
202       s->Printf(", value = 0x%16.16" PRIx64,
203                 m_addr_range.GetBaseAddress().GetOffset());
204   }
205   ConstString demangled = GetMangled().GetDemangledName();
206   if (demangled)
207     s->Printf(", name=\"%s\"", demangled.AsCString());
208   if (m_mangled.GetMangledName())
209     s->Printf(", mangled=\"%s\"", m_mangled.GetMangledName().AsCString());
210 }
211 
212 void Symbol::Dump(Stream *s, Target *target, uint32_t index,
213                   Mangled::NamePreference name_preference) const {
214   s->Printf("[%5u] %6u %c%c%c %-15s ", index, GetID(), m_is_debug ? 'D' : ' ',
215             m_is_synthetic ? 'S' : ' ', m_is_external ? 'X' : ' ',
216             GetTypeAsString());
217 
218   // Make sure the size of the symbol is up to date before dumping
219   GetByteSize();
220 
221   ConstString name = GetMangled().GetName(name_preference);
222   if (ValueIsAddress()) {
223     if (!m_addr_range.GetBaseAddress().Dump(s, nullptr,
224                                             Address::DumpStyleFileAddress))
225       s->Printf("%*s", 18, "");
226 
227     s->PutChar(' ');
228 
229     if (!m_addr_range.GetBaseAddress().Dump(s, target,
230                                             Address::DumpStyleLoadAddress))
231       s->Printf("%*s", 18, "");
232 
233     const char *format = m_size_is_sibling ? " Sibling -> [%5llu] 0x%8.8x %s\n"
234                                            : " 0x%16.16" PRIx64 " 0x%8.8x %s\n";
235     s->Printf(format, GetByteSize(), m_flags, name.AsCString(""));
236   } else if (m_type == eSymbolTypeReExported) {
237     s->Printf(
238         "                                                         0x%8.8x %s",
239         m_flags, name.AsCString(""));
240 
241     ConstString reexport_name = GetReExportedSymbolName();
242     intptr_t shlib = m_addr_range.GetByteSize();
243     if (shlib)
244       s->Printf(" -> %s`%s\n", (const char *)shlib, reexport_name.GetCString());
245     else
246       s->Printf(" -> %s\n", reexport_name.GetCString());
247   } else {
248     const char *format =
249         m_size_is_sibling
250             ? "0x%16.16" PRIx64
251               "                    Sibling -> [%5llu] 0x%8.8x %s\n"
252             : "0x%16.16" PRIx64 "                    0x%16.16" PRIx64
253               " 0x%8.8x %s\n";
254     s->Printf(format, m_addr_range.GetBaseAddress().GetOffset(), GetByteSize(),
255               m_flags, name.AsCString(""));
256   }
257 }
258 
259 uint32_t Symbol::GetPrologueByteSize() {
260   if (m_type == eSymbolTypeCode || m_type == eSymbolTypeResolver) {
261     if (!m_type_data_resolved) {
262       m_type_data_resolved = true;
263 
264       const Address &base_address = m_addr_range.GetBaseAddress();
265       Function *function = base_address.CalculateSymbolContextFunction();
266       if (function) {
267         // Functions have line entries which can also potentially have end of
268         // prologue information. So if this symbol points to a function, use
269         // the prologue information from there.
270         m_type_data = function->GetPrologueByteSize();
271       } else {
272         ModuleSP module_sp(base_address.GetModule());
273         SymbolContext sc;
274         if (module_sp) {
275           uint32_t resolved_flags = module_sp->ResolveSymbolContextForAddress(
276               base_address, eSymbolContextLineEntry, sc);
277           if (resolved_flags & eSymbolContextLineEntry) {
278             // Default to the end of the first line entry.
279             m_type_data = sc.line_entry.range.GetByteSize();
280 
281             // Set address for next line.
282             Address addr(base_address);
283             addr.Slide(m_type_data);
284 
285             // Check the first few instructions and look for one that has a
286             // line number that is different than the first entry. This is also
287             // done in Function::GetPrologueByteSize().
288             uint16_t total_offset = m_type_data;
289             for (int idx = 0; idx < 6; ++idx) {
290               SymbolContext sc_temp;
291               resolved_flags = module_sp->ResolveSymbolContextForAddress(
292                   addr, eSymbolContextLineEntry, sc_temp);
293               // Make sure we got line number information...
294               if (!(resolved_flags & eSymbolContextLineEntry))
295                 break;
296 
297               // If this line number is different than our first one, use it
298               // and we're done.
299               if (sc_temp.line_entry.line != sc.line_entry.line) {
300                 m_type_data = total_offset;
301                 break;
302               }
303 
304               // Slide addr up to the next line address.
305               addr.Slide(sc_temp.line_entry.range.GetByteSize());
306               total_offset += sc_temp.line_entry.range.GetByteSize();
307               // If we've gone too far, bail out.
308               if (total_offset >= m_addr_range.GetByteSize())
309                 break;
310             }
311 
312             // Sanity check - this may be a function in the middle of code that
313             // has debug information, but not for this symbol.  So the line
314             // entries surrounding us won't lie inside our function. In that
315             // case, the line entry will be bigger than we are, so we do that
316             // quick check and if that is true, we just return 0.
317             if (m_type_data >= m_addr_range.GetByteSize())
318               m_type_data = 0;
319           } else {
320             // TODO: expose something in Process to figure out the
321             // size of a function prologue.
322             m_type_data = 0;
323           }
324         }
325       }
326     }
327     return m_type_data;
328   }
329   return 0;
330 }
331 
332 bool Symbol::Compare(ConstString name, SymbolType type) const {
333   if (type == eSymbolTypeAny || m_type == type) {
334     const Mangled &mangled = GetMangled();
335     return mangled.GetMangledName() == name ||
336            mangled.GetDemangledName() == name;
337   }
338   return false;
339 }
340 
341 #define ENUM_TO_CSTRING(x)                                                     \
342   case eSymbolType##x:                                                         \
343     return #x;
344 
345 const char *Symbol::GetTypeAsString() const {
346   switch (m_type) {
347     ENUM_TO_CSTRING(Invalid);
348     ENUM_TO_CSTRING(Absolute);
349     ENUM_TO_CSTRING(Code);
350     ENUM_TO_CSTRING(Resolver);
351     ENUM_TO_CSTRING(Data);
352     ENUM_TO_CSTRING(Trampoline);
353     ENUM_TO_CSTRING(Runtime);
354     ENUM_TO_CSTRING(Exception);
355     ENUM_TO_CSTRING(SourceFile);
356     ENUM_TO_CSTRING(HeaderFile);
357     ENUM_TO_CSTRING(ObjectFile);
358     ENUM_TO_CSTRING(CommonBlock);
359     ENUM_TO_CSTRING(Block);
360     ENUM_TO_CSTRING(Local);
361     ENUM_TO_CSTRING(Param);
362     ENUM_TO_CSTRING(Variable);
363     ENUM_TO_CSTRING(VariableType);
364     ENUM_TO_CSTRING(LineEntry);
365     ENUM_TO_CSTRING(LineHeader);
366     ENUM_TO_CSTRING(ScopeBegin);
367     ENUM_TO_CSTRING(ScopeEnd);
368     ENUM_TO_CSTRING(Additional);
369     ENUM_TO_CSTRING(Compiler);
370     ENUM_TO_CSTRING(Instrumentation);
371     ENUM_TO_CSTRING(Undefined);
372     ENUM_TO_CSTRING(ObjCClass);
373     ENUM_TO_CSTRING(ObjCMetaClass);
374     ENUM_TO_CSTRING(ObjCIVar);
375     ENUM_TO_CSTRING(ReExported);
376   default:
377     break;
378   }
379   return "<unknown SymbolType>";
380 }
381 
382 void Symbol::CalculateSymbolContext(SymbolContext *sc) {
383   // Symbols can reconstruct the symbol and the module in the symbol context
384   sc->symbol = this;
385   if (ValueIsAddress())
386     sc->module_sp = GetAddressRef().GetModule();
387   else
388     sc->module_sp.reset();
389 }
390 
391 ModuleSP Symbol::CalculateSymbolContextModule() {
392   if (ValueIsAddress())
393     return GetAddressRef().GetModule();
394   return ModuleSP();
395 }
396 
397 Symbol *Symbol::CalculateSymbolContextSymbol() { return this; }
398 
399 void Symbol::DumpSymbolContext(Stream *s) {
400   bool dumped_module = false;
401   if (ValueIsAddress()) {
402     ModuleSP module_sp(GetAddressRef().GetModule());
403     if (module_sp) {
404       dumped_module = true;
405       module_sp->DumpSymbolContext(s);
406     }
407   }
408   if (dumped_module)
409     s->PutCString(", ");
410 
411   s->Printf("Symbol{0x%8.8x}", GetID());
412 }
413 
414 lldb::addr_t Symbol::GetByteSize() const { return m_addr_range.GetByteSize(); }
415 
416 Symbol *Symbol::ResolveReExportedSymbolInModuleSpec(
417     Target &target, ConstString &reexport_name, ModuleSpec &module_spec,
418     ModuleList &seen_modules) const {
419   ModuleSP module_sp;
420   if (module_spec.GetFileSpec()) {
421     // Try searching for the module file spec first using the full path
422     module_sp = target.GetImages().FindFirstModule(module_spec);
423     if (!module_sp) {
424       // Next try and find the module by basename in case environment variables
425       // or other runtime trickery causes shared libraries to be loaded from
426       // alternate paths
427       module_spec.GetFileSpec().GetDirectory().Clear();
428       module_sp = target.GetImages().FindFirstModule(module_spec);
429     }
430   }
431 
432   if (module_sp) {
433     // There should not be cycles in the reexport list, but we don't want to
434     // crash if there are so make sure we haven't seen this before:
435     if (!seen_modules.AppendIfNeeded(module_sp))
436       return nullptr;
437 
438     lldb_private::SymbolContextList sc_list;
439     module_sp->FindSymbolsWithNameAndType(reexport_name, eSymbolTypeAny,
440                                           sc_list);
441     const size_t num_scs = sc_list.GetSize();
442     if (num_scs > 0) {
443       for (size_t i = 0; i < num_scs; ++i) {
444         lldb_private::SymbolContext sc;
445         if (sc_list.GetContextAtIndex(i, sc)) {
446           if (sc.symbol->IsExternal())
447             return sc.symbol;
448         }
449       }
450     }
451     // If we didn't find the symbol in this module, it may be because this
452     // module re-exports some whole other library.  We have to search those as
453     // well:
454     seen_modules.Append(module_sp);
455 
456     FileSpecList reexported_libraries =
457         module_sp->GetObjectFile()->GetReExportedLibraries();
458     size_t num_reexported_libraries = reexported_libraries.GetSize();
459     for (size_t idx = 0; idx < num_reexported_libraries; idx++) {
460       ModuleSpec reexported_module_spec;
461       reexported_module_spec.GetFileSpec() =
462           reexported_libraries.GetFileSpecAtIndex(idx);
463       Symbol *result_symbol = ResolveReExportedSymbolInModuleSpec(
464           target, reexport_name, reexported_module_spec, seen_modules);
465       if (result_symbol)
466         return result_symbol;
467     }
468   }
469   return nullptr;
470 }
471 
472 Symbol *Symbol::ResolveReExportedSymbol(Target &target) const {
473   ConstString reexport_name(GetReExportedSymbolName());
474   if (reexport_name) {
475     ModuleSpec module_spec;
476     ModuleList seen_modules;
477     module_spec.GetFileSpec() = GetReExportedSymbolSharedLibrary();
478     if (module_spec.GetFileSpec()) {
479       return ResolveReExportedSymbolInModuleSpec(target, reexport_name,
480                                                  module_spec, seen_modules);
481     }
482   }
483   return nullptr;
484 }
485 
486 lldb::addr_t Symbol::GetFileAddress() const {
487   if (ValueIsAddress())
488     return GetAddressRef().GetFileAddress();
489   else
490     return LLDB_INVALID_ADDRESS;
491 }
492 
493 lldb::addr_t Symbol::GetLoadAddress(Target *target) const {
494   if (ValueIsAddress())
495     return GetAddressRef().GetLoadAddress(target);
496   else
497     return LLDB_INVALID_ADDRESS;
498 }
499 
500 ConstString Symbol::GetName() const { return GetMangled().GetName(); }
501 
502 ConstString Symbol::GetNameNoArguments() const {
503   return GetMangled().GetName(Mangled::ePreferDemangledWithoutArguments);
504 }
505 
506 lldb::addr_t Symbol::ResolveCallableAddress(Target &target) const {
507   if (GetType() == lldb::eSymbolTypeUndefined)
508     return LLDB_INVALID_ADDRESS;
509 
510   Address func_so_addr;
511 
512   bool is_indirect = IsIndirect();
513   if (GetType() == eSymbolTypeReExported) {
514     Symbol *reexported_symbol = ResolveReExportedSymbol(target);
515     if (reexported_symbol) {
516       func_so_addr = reexported_symbol->GetAddress();
517       is_indirect = reexported_symbol->IsIndirect();
518     }
519   } else {
520     func_so_addr = GetAddress();
521     is_indirect = IsIndirect();
522   }
523 
524   if (func_so_addr.IsValid()) {
525     if (!target.GetProcessSP() && is_indirect) {
526       // can't resolve indirect symbols without calling a function...
527       return LLDB_INVALID_ADDRESS;
528     }
529 
530     lldb::addr_t load_addr =
531         func_so_addr.GetCallableLoadAddress(&target, is_indirect);
532 
533     if (load_addr != LLDB_INVALID_ADDRESS) {
534       return load_addr;
535     }
536   }
537 
538   return LLDB_INVALID_ADDRESS;
539 }
540 
541 lldb::DisassemblerSP Symbol::GetInstructions(const ExecutionContext &exe_ctx,
542                                              const char *flavor,
543                                              bool prefer_file_cache) {
544   ModuleSP module_sp(m_addr_range.GetBaseAddress().GetModule());
545   if (module_sp && exe_ctx.HasTargetScope()) {
546     return Disassembler::DisassembleRange(module_sp->GetArchitecture(), nullptr,
547                                           flavor, exe_ctx.GetTargetRef(),
548                                           m_addr_range, !prefer_file_cache);
549   }
550   return lldb::DisassemblerSP();
551 }
552 
553 bool Symbol::GetDisassembly(const ExecutionContext &exe_ctx, const char *flavor,
554                             bool prefer_file_cache, Stream &strm) {
555   lldb::DisassemblerSP disassembler_sp =
556       GetInstructions(exe_ctx, flavor, prefer_file_cache);
557   if (disassembler_sp) {
558     const bool show_address = true;
559     const bool show_bytes = false;
560     disassembler_sp->GetInstructionList().Dump(&strm, show_address, show_bytes,
561                                                &exe_ctx);
562     return true;
563   }
564   return false;
565 }
566 
567 bool Symbol::ContainsFileAddress(lldb::addr_t file_addr) const {
568   return m_addr_range.ContainsFileAddress(file_addr);
569 }
570 
571 bool Symbol::IsSyntheticWithAutoGeneratedName() const {
572   if (!IsSynthetic())
573     return false;
574   if (!m_mangled)
575     return true;
576   ConstString demangled = m_mangled.GetDemangledName();
577   return demangled.GetStringRef().startswith(GetSyntheticSymbolPrefix());
578 }
579 
580 void Symbol::SynthesizeNameIfNeeded() const {
581   if (m_is_synthetic && !m_mangled) {
582     // Synthetic symbol names don't mean anything, but they do uniquely
583     // identify individual symbols so we give them a unique name. The name
584     // starts with the synthetic symbol prefix, followed by a unique number.
585     // Typically the UserID of a real symbol is the symbol table index of the
586     // symbol in the object file's symbol table(s), so it will be the same
587     // every time you read in the object file. We want the same persistence for
588     // synthetic symbols so that users can identify them across multiple debug
589     // sessions, to understand crashes in those symbols and to reliably set
590     // breakpoints on them.
591     llvm::SmallString<256> name;
592     llvm::raw_svector_ostream os(name);
593     os << GetSyntheticSymbolPrefix() << GetID();
594     m_mangled.SetDemangledName(ConstString(os.str()));
595   }
596 }
597