Code change to avoid signed/unsigned mismatch warnings

core/fpdfapi/fpdf_parser/cpdf_indirect_object_holder.cpp

 // Copyright 2016 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 "core/fpdfapi/fpdf_parser/include/cpdf_indirect_object_holder.h"
 
 #include "core/fpdfapi/fpdf_parser/include/cpdf_object.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_parser.h"
 
 CPDF_IndirectObjectHolder::CPDF_IndirectObjectHolder(CPDF_Parser* pParser)
     : m_pParser(pParser), m_LastObjNum(0) {
   if (pParser)
     m_LastObjNum = m_pParser->GetLastObjNum();
 }
 
 CPDF_IndirectObjectHolder::~CPDF_IndirectObjectHolder() {
   for (const auto& pair : m_IndirectObjs)
     pair.second->Destroy();
 }
 
 CPDF_Object* CPDF_IndirectObjectHolder::GetIndirectObject(uint32_t objnum) {
   if (objnum == 0)
     return nullptr;
 
   auto it = m_IndirectObjs.find(objnum);
   if (it != m_IndirectObjs.end())
-    return it->second->GetObjNum() != -1 ? it->second : nullptr;
+    return it->second->GetObjNum() != CPDF_Object::kInvalidObjNum ? it->second
+                                                                  : nullptr;
 
   if (!m_pParser)
     return nullptr;
 
   CPDF_Object* pObj = m_pParser->ParseIndirectObject(this, objnum);
   if (!pObj)
     return nullptr;
 
   pObj->m_ObjNum = objnum;
   m_LastObjNum = std::max(m_LastObjNum, objnum);
   if (m_IndirectObjs[objnum])
     m_IndirectObjs[objnum]->Destroy();
 
   m_IndirectObjs[objnum] = pObj;
   return pObj;
 }
 
 uint32_t CPDF_IndirectObjectHolder::AddIndirectObject(CPDF_Object* pObj) {
   if (pObj->m_ObjNum)
     return pObj->m_ObjNum;
 
   m_LastObjNum++;
   m_IndirectObjs[m_LastObjNum] = pObj;
   pObj->m_ObjNum = m_LastObjNum;
   return m_LastObjNum;
 }
 
 void CPDF_IndirectObjectHolder::ReleaseIndirectObject(uint32_t objnum) {
   auto it = m_IndirectObjs.find(objnum);
-  if (it == m_IndirectObjs.end() || it->second->GetObjNum() == -1)
+  if (it == m_IndirectObjs.end() ||
+      it->second->GetObjNum() == CPDF_Object::kInvalidObjNum) {
     return;
+  }
   it->second->Destroy();
   m_IndirectObjs.erase(it);
 }
 
 FX_BOOL CPDF_IndirectObjectHolder::InsertIndirectObject(uint32_t objnum,
                                                         CPDF_Object* pObj) {
   if (!objnum || !pObj)
     return FALSE;
   auto it = m_IndirectObjs.find(objnum);
   if (it != m_IndirectObjs.end()) {
     if (pObj->GetGenNum() <= it->second->GetGenNum()) {
       pObj->Destroy();
       return FALSE;
     }
     it->second->Destroy();
   }
   pObj->m_ObjNum = objnum;
   m_IndirectObjs[objnum] = pObj;
   m_LastObjNum = std::max(m_LastObjNum, objnum);
   return TRUE;
 }