[lldb/DWARF] Fix a leak in line table construction

We were creating a bunch of LineSequence objects but never deleting
them.

This fixes the leak and changes the code to use std::unique_ptr, to make
it harder to make the same mistake again.

Author: labath

lldb/include/lldb/Symbol/LineTable.h

@@ -46,7 +46,8 @@ class LineTable {
   ///
   /// \param[in] sequences
   ///     Unsorted list of line sequences.
-  LineTable(CompileUnit *comp_unit, std::vector<LineSequence *> &sequences);
+  LineTable(CompileUnit *comp_unit,
+            std::vector<std::unique_ptr<LineSequence>> &&sequences);
 
   /// Destructor.
   ~LineTable();
@@ -70,7 +71,7 @@ class LineTable {
                        bool is_epilogue_begin, bool is_terminal_entry);
 
   // Used to instantiate the LineSequence helper class
-  static LineSequence *CreateLineSequenceContainer();
+  static std::unique_ptr<LineSequence> CreateLineSequenceContainer();
 
   // Append an entry to a caller-provided collection that will later be
   // inserted in this line table.
@@ -265,7 +266,8 @@ class LineTable {
     public:
       LessThanBinaryPredicate(LineTable *line_table);
       bool operator()(const LineTable::Entry &, const LineTable::Entry &) const;
-      bool operator()(const LineSequence*, const LineSequence*) const;
+      bool operator()(const std::unique_ptr<LineSequence> &,
+                      const std::unique_ptr<LineSequence> &) const;
 
     protected:
       LineTable *m_line_table;

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

@@ -995,21 +995,22 @@ bool SymbolFileDWARF::ParseLineTable(CompileUnit &comp_unit) {
   // FIXME: Rather than parsing the whole line table and then copying it over
   // into LLDB, we should explore using a callback to populate the line table
   // while we parse to reduce memory usage.
-  LineSequence *sequence = LineTable::CreateLineSequenceContainer();
-  std::vector<LineSequence *> sequences;
+  std::unique_ptr<LineSequence> sequence =
+      LineTable::CreateLineSequenceContainer();
+  std::vector<std::unique_ptr<LineSequence>> sequences;
   for (auto &row : line_table->Rows) {
     LineTable::AppendLineEntryToSequence(
-        sequence, row.Address.Address, row.Line, row.Column, row.File,
+        sequence.get(), row.Address.Address, row.Line, row.Column, row.File,
         row.IsStmt, row.BasicBlock, row.PrologueEnd, row.EpilogueBegin,
         row.EndSequence);
     if (row.EndSequence) {
-      sequences.push_back(sequence);
+      sequences.push_back(std::move(sequence));
       sequence = LineTable::CreateLineSequenceContainer();
     }
   }
 
   std::unique_ptr<LineTable> line_table_up =
-      std::make_unique<LineTable>(&comp_unit, sequences);
+      std::make_unique<LineTable>(&comp_unit, std::move(sequences));
 
   if (SymbolFileDWARFDebugMap *debug_map_symfile = GetDebugMapSymfile()) {
     // We have an object file that has a line table with addresses that are not

lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.cpp

@@ -1817,7 +1817,7 @@ bool SymbolFilePDB::ParseCompileUnitLineTable(CompileUnit &comp_unit,
             prev_source_idx, false, false, false, false, true);
 
         line_table->InsertSequence(sequence.release());
-        sequence.reset(line_table->CreateLineSequenceContainer());
+        sequence = line_table->CreateLineSequenceContainer();
       }
 
       if (ShouldAddLine(match_line, lno, length)) {
@@ -1854,7 +1854,7 @@ bool SymbolFilePDB::ParseCompileUnitLineTable(CompileUnit &comp_unit,
           prev_source_idx, false, false, false, false, true);
     }
 
-    line_table->InsertSequence(sequence.release());
+    line_table->InsertSequence(sequence.get());
   }
 
   if (line_table->GetSize()) {

lldb/source/Symbol/LineTable.cpp

@@ -21,14 +21,15 @@ using namespace lldb_private;
 LineTable::LineTable(CompileUnit *comp_unit)
     : m_comp_unit(comp_unit), m_entries() {}
 
-LineTable::LineTable(CompileUnit *comp_unit, std::vector<LineSequence *> &sequences)
+LineTable::LineTable(CompileUnit *comp_unit,
+                     std::vector<std::unique_ptr<LineSequence>> &&sequences)
     : m_comp_unit(comp_unit), m_entries() {
   LineTable::Entry::LessThanBinaryPredicate less_than_bp(this);
   llvm::stable_sort(sequences, less_than_bp);
-  for (auto *sequence : sequences) {
-    LineSequenceImpl *seq = reinterpret_cast<LineSequenceImpl *>(sequence);
+  for (const auto &sequence : sequences) {
+    LineSequenceImpl *seq = static_cast<LineSequenceImpl *>(sequence.get());
     m_entries.insert(m_entries.end(), seq->m_entries.begin(),
-      seq->m_entries.end());
+                     seq->m_entries.end());
   }
 }
 
@@ -61,8 +62,8 @@ LineSequence::LineSequence() {}
 
 void LineTable::LineSequenceImpl::Clear() { m_entries.clear(); }
 
-LineSequence *LineTable::CreateLineSequenceContainer() {
-  return new LineTable::LineSequenceImpl();
+std::unique_ptr<LineSequence> LineTable::CreateLineSequenceContainer() {
+  return std::make_unique<LineTable::LineSequenceImpl>();
 }
 
 void LineTable::AppendLineEntryToSequence(
@@ -166,9 +167,10 @@ operator()(const LineTable::Entry &a, const LineTable::Entry &b) const {
 }
 
 bool LineTable::Entry::LessThanBinaryPredicate::
-operator()(const LineSequence *sequence_a, const LineSequence *sequence_b) const {
-  auto *seq_a = static_cast<const LineSequenceImpl *>(sequence_a);
-  auto *seq_b = static_cast<const LineSequenceImpl *>(sequence_b);
+operator()(const std::unique_ptr<LineSequence> &sequence_a,
+           const std::unique_ptr<LineSequence> &sequence_b) const {
+  auto *seq_a = static_cast<const LineSequenceImpl *>(sequence_a.get());
+  auto *seq_b = static_cast<const LineSequenceImpl *>(sequence_b.get());
   return (*this)(seq_a->m_entries.front(), seq_b->m_entries.front());
 }