Index: source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h
+++ source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.h
@@ -31,6 +31,7 @@
   DWARFCompileUnit(SymbolFileDWARF *dwarf2Data);
   ~DWARFCompileUnit();
 
+  // Object must be clear - either constructed now or after calling Clear().
   bool Extract(const lldb_private::DWARFDataExtractor &debug_info,
                lldb::offset_t *offset_ptr);
   size_t ExtractDIEsIfNeeded(bool cu_die_only);
Index: source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp
@@ -71,8 +71,7 @@
 
 bool DWARFCompileUnit::Extract(const DWARFDataExtractor &debug_info,
                                lldb::offset_t *offset_ptr) {
-  Clear();
-
+  assert(m_offset == DW_INVALID_OFFSET);
   m_offset = *offset_ptr;
 
   if (debug_info.ValidOffset(*offset_ptr)) {
Index: source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
===================================================================
--- source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -293,6 +293,8 @@
       // and create a new one for our own use!
       if (!cu.unique())
         cu.reset(new DWARFCompileUnit(dwarf2Data));
+      else
+        cu->Clear();
 
       // Make sure we start on a proper
       offset = next_cu_offset;