[lldb] Don't clear a Module's UnwindTable when adding a SymbolFile (#86603)

lldb/include/lldb/Symbol/UnwindTable.h

@@ -57,6 +57,10 @@ class UnwindTable {
 
   ArchSpec GetArchitecture();
 
+  /// Called after a SymbolFile has been added to a Module to add any new
+  /// unwind sections that may now be available.
+  void Update();
+
 private:
   void Dump(Stream &s);
 

lldb/source/Core/Module.cpp

@@ -1046,6 +1046,8 @@ SymbolFile *Module::GetSymbolFile(bool can_create, Stream *feedback_strm) {
         m_symfile_up.reset(
             SymbolVendor::FindPlugin(shared_from_this(), feedback_strm));
         m_did_load_symfile = true;
+        if (m_unwind_table)
+          m_unwind_table->Update();
       }
     }
   }
@@ -1371,9 +1373,9 @@ void Module::SectionFileAddressesChanged() {
 
 UnwindTable &Module::GetUnwindTable() {
   if (!m_unwind_table) {
-    m_unwind_table.emplace(*this);
     if (!m_symfile_spec)
       SymbolLocator::DownloadSymbolFileAsync(GetUUID());
+    m_unwind_table.emplace(*this);
   }
   return *m_unwind_table;
 }
@@ -1491,15 +1493,10 @@ void Module::SetSymbolFileFileSpec(const FileSpec &file) {
         // one
         obj_file->ClearSymtab();
 
-        // Clear the unwind table too, as that may also be affected by the
-        // symbol file information.
-        m_unwind_table.reset();
-
         // The symbol file might be a directory bundle ("/tmp/a.out.dSYM")
         // instead of a full path to the symbol file within the bundle
         // ("/tmp/a.out.dSYM/Contents/Resources/DWARF/a.out"). So we need to
         // check this
-
         if (FileSystem::Instance().IsDirectory(file)) {
           std::string new_path(file.GetPath());
           std::string old_path(obj_file->GetFileSpec().GetPath());

lldb/source/Symbol/UnwindTable.cpp

@@ -84,6 +84,51 @@ void UnwindTable::Initialize() {
   }
 }
 
+void UnwindTable::Update() {
+  if (!m_initialized)
+    return Initialize();
+
+  std::lock_guard<std::mutex> guard(m_mutex);
+
+  ObjectFile *object_file = m_module.GetObjectFile();
+  if (!object_file)
+    return;
+
+  if (!m_object_file_unwind_up)
+    m_object_file_unwind_up = object_file->CreateCallFrameInfo();
+
+  SectionList *sl = m_module.GetSectionList();
+  if (!sl)
+    return;
+
+  SectionSP sect = sl->FindSectionByType(eSectionTypeEHFrame, true);
+  if (!m_eh_frame_up && sect) {
+    m_eh_frame_up = std::make_unique<DWARFCallFrameInfo>(
+        *object_file, sect, DWARFCallFrameInfo::EH);
+  }
+
+  sect = sl->FindSectionByType(eSectionTypeDWARFDebugFrame, true);
+  if (!m_debug_frame_up && sect) {
+    m_debug_frame_up = std::make_unique<DWARFCallFrameInfo>(
+        *object_file, sect, DWARFCallFrameInfo::DWARF);
+  }
+
+  sect = sl->FindSectionByType(eSectionTypeCompactUnwind, true);
+  if (!m_compact_unwind_up && sect) {
+    m_compact_unwind_up =
+        std::make_unique<CompactUnwindInfo>(*object_file, sect);
+  }
+
+  sect = sl->FindSectionByType(eSectionTypeARMexidx, true);
+  if (!m_arm_unwind_up && sect) {
+    SectionSP sect_extab = sl->FindSectionByType(eSectionTypeARMextab, true);
+    if (sect_extab.get()) {
+      m_arm_unwind_up =
+          std::make_unique<ArmUnwindInfo>(*object_file, sect, sect_extab);
+    }
+  }
+}
+
 UnwindTable::~UnwindTable() = default;
 
 std::optional<AddressRange>