Cpp Target：we found memory-leak in LexerATNSimulator::computeTargetState

[tangxing806]

• target:Cpp
• antlr tags : 4.9.2
• we found memory-leak in LexerATNSimulator::computeTargetState

dfa::DFAState *LexerATNSimulator::computeTargetState(CharStream *input, dfa::DFAState *s, size_t t) {
  OrderedATNConfigSet *reach = new OrderedATNConfigSet(); /* mem-check: deleted on error or managed by new DFA state. */

  // if we don't find an existing DFA state
  // Fill reach starting from closure, following t transitions
  getReachableConfigSet(input, s->configs.get(), reach, t);

  if (reach->isEmpty()) { // we got nowhere on t from s
    if (!reach->hasSemanticContext) {
      // we got nowhere on t, don't throw out this knowledge; it'd
      // cause a failover from DFA later.
      delete reach;
      addDFAEdge(s, t, ERROR.get());
    }

    // stop when we can't match any more char
    return ERROR.get();
  }

  // Add an edge from s to target DFA found/created for reach
  return addDFAEdge(s, t, reach);
}

after my modify：only add delete reach

dfa::DFAState *LexerATNSimulator::computeTargetState(CharStream *input, dfa::DFAState *s, size_t t) {
  OrderedATNConfigSet *reach = new OrderedATNConfigSet(); /* mem-check: deleted on error or managed by new DFA state. */

  // if we don't find an existing DFA state
  // Fill reach starting from closure, following t transitions
  getReachableConfigSet(input, s->configs.get(), reach, t);

  if (reach->isEmpty()) { // we got nowhere on t from s
    if (!reach->hasSemanticContext) {
      // we got nowhere on t, don't throw out this knowledge; it'd
      // cause a failover from DFA later.
      delete reach;
      addDFAEdge(s, t, ERROR.get());
    } else {
      delete reach;                                       // <<--------------------------- we modify here 
    }

    // stop when we can't match any more char
    return ERROR.get();
  }

  // Add an edge from s to target DFA found/created for reach
  return addDFAEdge(s, t, reach);
}

now, memory-leak disappear.
Due to the big grammar size and company policy, we can't provide the test grammar.

Sorry for that.

Is the above modifications reasonable and the best?

[jcking]

The delete can be moved after the enclosing if statement instead of adding an additional else. I proposed a patch #3374.

[jcking]

This should be resolved. @mike-lischke

[tangxing806]

thanks！

[mike-lischke]

Yes, so I think this issue can be closed.