Don't leave dangling pointer to out-of-scope local in CPDF_StreamContentParser::Parse.

core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.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 "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fxcodec/fx_codec.h"
 #include "pageint.h"
@@ skipping 13 matching lines @@
         return FALSE;
     }
     FX_BYTE ch;
     while((ch = *op++)) {
         if(_PDF_OpCharType[ch] == 'I') {
             return TRUE;
         }
     }
     return FALSE;
 }
+class CPDF_StreamParserAutoClearer {
+  public:
+    CPDF_StreamParserAutoClearer(CPDF_StreamParser** scoped_variable, CPDF_StreamParser* new_parser)
+            : scoped_variable_(scoped_variable) {
+        *scoped_variable_ = new_parser;

[jun_fang, 2014/10/14 20:54:08]

nit: shall we check whether scoped_variable_ is not NULL?

+    }
+    ~CPDF_StreamParserAutoClearer() { *scoped_variable_ = NULL; }
+  private:
+    CPDF_StreamParser** scoped_variable_;
+};
 FX_DWORD CPDF_StreamContentParser::Parse(FX_LPCBYTE pData, FX_DWORD dwSize, FX_DWORD max_cost)
 {
     if (m_Level > _FPDF_MAX_FORM_LEVEL_) {
         return dwSize;
     }
     FX_DWORD InitObjCount = m_pObjectList->CountObjects();
     CPDF_StreamParser syntax(pData, dwSize);
-    m_pSyntax = &syntax;
+    CPDF_StreamParserAutoClearer auto_clearer(&m_pSyntax, &syntax);
     m_CompatCount = 0;
     while (1) {
         FX_DWORD cost = m_pObjectList->CountObjects() - InitObjCount;
         if (max_cost && cost >= max_cost) {
             break;
         }
         switch (syntax.ParseNextElement()) {
             case CPDF_StreamParser::EndOfData:
                 return m_pSyntax->GetPos();
             case CPDF_StreamParser::Keyword:
@@ skipping 1084 matching lines @@
         return 100;
     }
     if (m_InternalStage == PAGEPARSE_STAGE_GETCONTENT) {
         return 10;
     }
     if (m_InternalStage == PAGEPARSE_STAGE_CHECKCLIP) {
         return 90;
     }
     return 10 + 80 * m_CurrentOffset / m_Size;
 }