[LLDB][NativePDB] Check string table in PDB files.

[zequanwu]

Summary

Usually PDB files have a string table (aka: Named Stream "/names" ). PDB for
some windows system libraries might not have that. This adds the check for it to
avoid crash in the absence of string table.

lldb/source/Plugins/SymbolFile/NativePDB/CompileUnitIndex.cpp

CompilandIndexItem &CompileUnitIndex::GetOrCreateCompiland(uint16_t modi) {
 
   cantFail(debug_stream.reload());
 
   cci = std::make_unique<CompilandIndexItem>(
       PdbCompilandId{modi}, std::move(debug_stream), std::move(descriptor));
   ParseExtendedInfo(m_index, *cci);
   ParseInlineeLineTableForCompileUnit(*cci);
 
+  auto strings = m_index.pdb().getStringTable();
+  if (strings) {
     cci->m_strings.initialize(cci->m_debug_stream.getSubsectionsArray());
-  PDBStringTable &strings = cantFail(m_index.pdb().getStringTable());
-  cci->m_strings.setStrings(strings.getStringTable());
+    cci->m_strings.setStrings(strings->getStringTable());
+  } else {
+    consumeError(strings.takeError());
+  }
 
   // We want the main source file to always comes first.  Note that we can't
   // just push_back the main file onto the front because `GetMainSourceFile`
   // computes it in such a way that it doesn't own the resulting memory.  So we
   // have to iterate the module file list comparing each one to the main file
   // name until we find it, and we can cache that one since the memory is backed
   // by a contiguous chunk inside the mapped PDB.
   llvm::SmallString<64> main_file = GetMainSourceFile(*cci);

lldb/source/Plugins/SymbolFile/NativePDB/PdbUtil.cpp

static bool GetFrameDataProgram(PdbIndex &index,
   const DebugFrameDataSubsectionRef &new_fpo_data =
       index.dbi().getNewFpoRecords();
 
   auto frame_data_it =
       GetCorrespondingFrameData(index.GetLoadAddress(), new_fpo_data, ranges);
   if (frame_data_it == new_fpo_data.end())
     return false;
 
-  PDBStringTable &strings = cantFail(index.pdb().getStringTable());
-  out_program = cantFail(strings.getStringForID(frame_data_it->FrameFunc));
+  auto strings = index.pdb().getStringTable();
+  if (!strings) {
+    consumeError(strings.takeError());
+    return false;
+  }
+  out_program = cantFail(strings->getStringForID(frame_data_it->FrameFunc));
   return true;
 }
 
 static RegisterId GetBaseFrameRegister(PdbIndex &index,
                                        PdbCompilandSymId frame_proc_id,
                                        bool is_parameter) {
   CVSymbol frame_proc_cvs = index.ReadSymbolRecord(frame_proc_id);
   if (frame_proc_cvs.kind() != S_FRAMEPROC)

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

 bool SymbolFileNativePDB::ParseDebugMacros(CompileUnit &comp_unit) {
   // PDB doesn't contain information about macros
   return false;
 }
 
 llvm::Expected<uint32_t>
 SymbolFileNativePDB::GetFileIndex(const CompilandIndexItem &cii,
                                   uint32_t file_id) {
+  if (!cii.m_strings.hasChecksums() || !cii.m_strings.hasStrings())
+    return llvm::make_error<RawError>(raw_error_code::no_entry);
+
   const auto &checksums = cii.m_strings.checksums().getArray();
   const auto &strings = cii.m_strings.strings();
   // Indices in this structure are actually offsets of records in the
   // DEBUG_S_FILECHECKSUMS subsection.  Those entries then have an index
   // into the global PDB string table.
   auto iter = checksums.at(file_id);
   if (iter == checksums.end())
     return llvm::make_error<RawError>(raw_error_code::no_entry);