void PDFiumEngine::Form_Print(IPDF_JSPLATFORM* param,
                              FPDF_BOOL ui,
                              int start,
                              int end,
                              FPDF_BOOL silent,
                              FPDF_BOOL shrink_to_fit,
                              FPDF_BOOL print_as_image,
                              FPDF_BOOL reverse,
                              FPDF_BOOL annotations) {
  PDFiumEngine* engine = static_cast<PDFiumEngine*>(param);
  engine->client_->Print();
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.