void PDFiumEngine::UnsupportedFeature(int type) {
  std::string feature;
  switch (type) {
#if !defined(PDF_ENABLE_XFA)
    case FPDF_UNSP_DOC_XFAFORM:
      feature = "XFA";
      break;
#endif
    case FPDF_UNSP_DOC_PORTABLECOLLECTION:
      feature = "Portfolios_Packages";
      break;
    case FPDF_UNSP_DOC_ATTACHMENT:
    case FPDF_UNSP_ANNOT_ATTACHMENT:
      feature = "Attachment";
      break;
    case FPDF_UNSP_DOC_SECURITY:
      feature = "Rights_Management";
      break;
    case FPDF_UNSP_DOC_SHAREDREVIEW:
      feature = "Shared_Review";
      break;
    case FPDF_UNSP_DOC_SHAREDFORM_ACROBAT:
    case FPDF_UNSP_DOC_SHAREDFORM_FILESYSTEM:
    case FPDF_UNSP_DOC_SHAREDFORM_EMAIL:
      feature = "Shared_Form";
      break;
    case FPDF_UNSP_ANNOT_3DANNOT:
      feature = "3D";
      break;
    case FPDF_UNSP_ANNOT_MOVIE:
      feature = "Movie";
      break;
    case FPDF_UNSP_ANNOT_SOUND:
      feature = "Sound";
      break;
    case FPDF_UNSP_ANNOT_SCREEN_MEDIA:
    case FPDF_UNSP_ANNOT_SCREEN_RICHMEDIA:
      feature = "Screen";
      break;
    case FPDF_UNSP_ANNOT_SIG:
      feature = "Digital_Signature";
      break;
  }
  client_->DocumentHasUnsupportedFeature(feature);
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.