Extern in .cpp file is a code smell, part 2.

fpdfsdk/src/fpdf_dataavail.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../public/fpdf_dataavail.h"
 #include "../include/fsdk_define.h"
 
-extern void ProcessParseError(FX_DWORD err_code);
 class CFPDF_FileAvailWrap : public IFX_FileAvail {
  public:
   CFPDF_FileAvailWrap() { m_pfileAvail = NULL; }
   ~CFPDF_FileAvailWrap() override {}
 
   void Set(FX_FILEAVAIL* pfileAvail) { m_pfileAvail = pfileAvail; }
 
   // IFX_FileAvail
   FX_BOOL IsDataAvail(FX_FILESIZE offset, FX_DWORD size) override {
     return m_pfileAvail->IsDataAvail(m_pfileAvail, offset, size);
@@ skipping 116 matching lines @@
     return -1;
   CFPDF_DownloadHintsWrap hints_wrap(hints);
   return ((CFPDF_DataAvail*)avail)->m_pDataAvail->IsFormAvail(&hints_wrap);
 }
 
 DLLEXPORT FPDF_BOOL STDCALL FPDFAvail_IsLinearized(FPDF_AVAIL avail) {
   if (avail == NULL)
     return -1;
   return ((CFPDF_DataAvail*)avail)->m_pDataAvail->IsLinearizedPDF();
 }