[lldb] Fix initialization of m_debug_cu_index_map

[alexander-shaposhnikov]

Summary

SymbolFileDWARFDwp contains m_debug_cu_index_map which was previously
initialized incorrectly: before m_debug_cu_index.parse is called m_debug_cu_index is empty,
thus the map was not actually getting populated properly.
This diff moves this step into a private helper method
and calls it after m_debug_cu_index.parse inside the public static method SymbolFileDWARFDwp::Create
(the constructor remains private).

Test plan:

Build a toy test example
main.cpp
clang -gsplit-dwarf -g -O0 main.cpp -o main.exe
llvm-dwp -e main.exe -o main.exe.dwp
Build LLDB with ENABLE_DEBUG_PRINTF set.
Run: lldb -- ./main.exe
Check that the indexes are now correct (before this change they were empty)
Check that debugging works (setting breakpoints, printing local variables (this was not working before))

[tberghammer]

Looks good, thanks for fixing it.

I am slightly confused why it was working for me when I tested it before submission but I must have messed up something during testing.

lldb/trunk/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.h

bool LoadSectionData(uint64_t dwo_id, lldb::SectionType sect_type,
                        lldb_private::DWARFDataExtractor &data);
 
 private:
   explicit SymbolFileDWARFDwp(lldb::ModuleSP module_sp,
                               lldb::ObjectFileSP obj_file);
 
   bool LoadRawSectionData(lldb::SectionType sect_type,
                           lldb_private::DWARFDataExtractor &data);
   
+  void InitDebugCUIndexMap();
+
   lldb::ObjectFileSP m_obj_file;
 
   std::mutex m_sections_mutex;
   std::map<lldb::SectionType, lldb_private::DWARFDataExtractor> m_sections;
 
   llvm::DWARFUnitIndex m_debug_cu_index;
   std::map<uint64_t, const llvm::DWARFUnitIndex::Entry *> m_debug_cu_index_map;
 };
 
 #endif // SymbolFileDWARFDwp_SymbolFileDWARFDwp_h_

lldb/trunk/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwp.cpp

if (!dwp_symfile->LoadRawSectionData(lldb::eSectionTypeDWARFDebugCuIndex,
     return nullptr;
 
   llvm::DataExtractor llvm_debug_cu_index(
       llvm::StringRef(debug_cu_index.PeekCStr(0), debug_cu_index.GetByteSize()),
       debug_cu_index.GetByteOrder() == lldb::eByteOrderLittle,
       debug_cu_index.GetAddressByteSize());
   if (!dwp_symfile->m_debug_cu_index.parse(llvm_debug_cu_index))
     return nullptr;
+  dwp_symfile->InitDebugCUIndexMap();
   return dwp_symfile;
 }
 
-SymbolFileDWARFDwp::SymbolFileDWARFDwp(lldb::ModuleSP module_sp,
-                                       lldb::ObjectFileSP obj_file)
-    : m_obj_file(std::move(obj_file)), m_debug_cu_index(llvm::DW_SECT_INFO) {
-  for (const auto &entry : m_debug_cu_index.getRows()) {
+void SymbolFileDWARFDwp::InitDebugCUIndexMap() {
+  m_debug_cu_index_map.clear();
+  for (const auto &entry : m_debug_cu_index.getRows())
     m_debug_cu_index_map.emplace(entry.getSignature(), &entry);
-  }
-}
+
+SymbolFileDWARFDwp::SymbolFileDWARFDwp(lldb::ModuleSP module_sp,
+                                       lldb::ObjectFileSP obj_file)
+    : m_obj_file(std::move(obj_file)), m_debug_cu_index(llvm::DW_SECT_INFO) 
+{}
 
 std::unique_ptr<SymbolFileDWARFDwo>
 SymbolFileDWARFDwp::GetSymbolFileForDwoId(DWARFCompileUnit *dwarf_cu,
                                           uint64_t dwo_id) {
   return std::unique_ptr<SymbolFileDWARFDwo>(
       new SymbolFileDWARFDwoDwp(this, m_obj_file, dwarf_cu, dwo_id));
 }