Re-enable several MSVC warnings

core/fxcrt/fx_basic_wstring.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 <stddef.h>
 
 #include <algorithm>
 #include <cctype>
@@ skipping 623 matching lines @@
   }
   FX_STRSIZE nSourceLen = FXSYS_wcslen(lpszOld);
   if (nSourceLen == 0) {
     return 0;
   }
   FX_STRSIZE nReplacementLen = lpszNew ? FXSYS_wcslen(lpszNew) : 0;
   FX_STRSIZE nCount = 0;
   FX_WCHAR* lpszStart = m_pData->m_String;
   FX_WCHAR* lpszEnd = m_pData->m_String + m_pData->m_nDataLength;
   FX_WCHAR* lpszTarget;
   {

[Tom Sepez, 2016/03/16 18:34:59]

nit: brace needed here?

[Wei Li, 2016/03/17 02:24:05]

Done.

-    while ((lpszTarget = (FX_WCHAR*)FXSYS_wcsstr(lpszStart, lpszOld)) &&
+    while ((lpszTarget = (FX_WCHAR*)FXSYS_wcsstr(lpszStart, lpszOld)) !=
+               nullptr &&
            lpszStart < lpszEnd) {

[Tom Sepez, 2016/03/16 18:34:59]

This should be fine.  Not sure we want to write it this way to make the compiler
happy.

[Wei Li, 2016/03/17 02:24:05]

For pdfium code, this warning is not that useful. But for some other cases,
people sometimes accidentally type "=" instead of "==". We have just a few (3 or
4?) cases like this to clean up. So I am fine following chromium code on this.  

       nCount++;
       lpszStart = lpszTarget + nSourceLen;
     }
   }
   if (nCount > 0) {
     CopyBeforeWrite();
     FX_STRSIZE nOldLength = m_pData->m_nDataLength;
     FX_STRSIZE nNewLength =
         nOldLength + (nReplacementLen - nSourceLen) * nCount;
     if (m_pData->m_nAllocLength < nNewLength || m_pData->m_nRefs > 1) {
       StringData* pOldData = m_pData;
       const FX_WCHAR* pstr = m_pData->m_String;
       m_pData = StringData::Create(nNewLength);
       if (!m_pData) {
         return 0;
       }
       FXSYS_memcpy(m_pData->m_String, pstr,
                    pOldData->m_nDataLength * sizeof(FX_WCHAR));
       pOldData->Release();
     }
     lpszStart = m_pData->m_String;
     lpszEnd = m_pData->m_String + std::max(m_pData->m_nDataLength, nNewLength);
     {
       while ((lpszTarget = (FX_WCHAR*)FXSYS_wcsstr(lpszStart, lpszOld)) !=
-                 NULL &&
+                 nullptr &&
              lpszStart < lpszEnd) {
         FX_STRSIZE nBalance =
             nOldLength -
             (FX_STRSIZE)(lpszTarget - m_pData->m_String + nSourceLen);
         FXSYS_memmove(lpszTarget + nReplacementLen, lpszTarget + nSourceLen,
                       nBalance * sizeof(FX_WCHAR));
         FXSYS_memcpy(lpszTarget, lpszNew, nReplacementLen * sizeof(FX_WCHAR));
         lpszStart = lpszTarget + nReplacementLen;
         lpszStart[nBalance] = 0;
         nOldLength += (nReplacementLen - nSourceLen);
@@ skipping 359 matching lines @@
   int dest_len =
       FXSYS_MultiByteToWideChar(codepage, 0, bstr, src_len, nullptr, 0);
   CFX_WideString wstr;
   if (dest_len) {
     FX_WCHAR* dest_buf = wstr.GetBuffer(dest_len);
     FXSYS_MultiByteToWideChar(codepage, 0, bstr, src_len, dest_buf, dest_len);
     wstr.ReleaseBuffer(dest_len);
   }
   return wstr;
 }