@Nullable
  @Override
  public String validateStack(final EOFLayout eofLayout) {
    WorkList workList = new WorkList(eofLayout.getCodeSectionCount());
    workList.put(0);
    int sectionToValidatie = workList.take();
    while (sectionToValidatie >= 0) {
      var validation = validateStack(sectionToValidatie, eofLayout, workList);
      if (validation != null) {
        return validation;
      }
      sectionToValidatie = workList.take();
    }
    if (!workList.isComplete()) {
      return format("Unreachable code section %d", workList.getFirstUnmarkedItem());
    }
    return null;
  }
validates the code section

@param code the code section code
@return null if valid, otherwise a string containing an error reason.
evm/src/main/java/org/hyperledger/besu/evm/code/CodeV1Validation.java