Extern in .cpp files is a code smell.

fpdfsdk/src/fsdk_mgr.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_ext.h"
 #include "../../third_party/base/nonstd_unique_ptr.h"
 #include "../include/fsdk_define.h"
 #include "../include/fsdk_mgr.h"
@@ skipping 898 matching lines @@
   if (CPDFSDK_Annot* pAnnot = GetFocusAnnot()) {
     CPDFDoc_Environment* pEnv = m_pSDKDoc->GetEnv();
     CPDFSDK_AnnotHandlerMgr* pAnnotHandlerMgr = pEnv->GetAnnotHandlerMgr();
     ASSERT(pAnnotHandlerMgr);
     return pAnnotHandlerMgr->Annot_OnKeyDown(pAnnot, nKeyCode, nFlag);
   }
   return FALSE;
 }
 
 FX_BOOL CPDFSDK_PageView::OnKeyUp(int nKeyCode, int nFlag) {
-  //  if(CPDFSDK_Annot* pAnnot = GetFocusAnnot())
-  //  {
-  //      CFFL_IFormFiller* pIFormFiller = g_pFormFillApp->GetIFormFiller();
-  //      return pIFormFiller->OnKeyUp(pAnnot, nKeyCode, nFlag);
-  //  }
   return FALSE;
 }
 
-extern void CheckUnSupportAnnot(CPDF_Document* pDoc, CPDF_Annot* pPDFAnnot);
-
 void CPDFSDK_PageView::LoadFXAnnots() {
   CPDFDoc_Environment* pEnv = m_pSDKDoc->GetEnv();
 
   FX_BOOL enableAPUpdate = CPDF_InterForm::UpdatingAPEnabled();
   // Disable the default AP construction.
   CPDF_InterForm::EnableUpdateAP(FALSE);
   m_pAnnotList = new CPDF_AnnotList(m_page);
   CPDF_InterForm::EnableUpdateAP(enableAPUpdate);
   int nCount = m_pAnnotList->Count();
   SetLock(TRUE);
@@ skipping 60 matching lines @@
   if (!pFocusAnnot)
     return NULL;
 
   for (int i = 0; i < m_fxAnnotArray.GetSize(); i++) {
     CPDFSDK_Annot* pAnnot = (CPDFSDK_Annot*)m_fxAnnotArray.GetAt(i);
     if (pAnnot == pFocusAnnot)
       return pAnnot;
   }
   return NULL;
 }