Re: CPtrArray/Heap failed...

"AliR \(VC++ MVP\)" <AliR@online.nospam>
Tue, 10 Mar 2009 09:45:53 -0500
How can that be a valid test if you don't know the size of the strings that
he is storing in the array?


"Giovanni Dicanio" <> wrote in message

"jjoohhnn" <> ha scritto nel messaggio

I have CPtrArray and CMapStringToString objects in my application.

I am creating strings on heap and storing address in CPtrArray object.

After that, reading strings from CPtrArray and process on this string
then store output string as a key/value in CMapStringToString object.

It is giving positive results in case of CPtrArray has 1,000,000 entries.

if CPtrArray has 4,000,000 entries, then after 1,000,000 + entry it is
giving null pointer. I could not read the strings from CPtrArray.

How to resolve this issue?


I tried a simple simulation of what I thought might be your scenario, but
using STL containers (which in some past experience I found better than
MFC containers to store big stuff, IMHO).

I tried with an STL std::vector of strings, and a std::map of strings to
strings, and the simple test seems OK to me on my machine with 3 GB of RAM
and 4,000,000 items in the array.

Here it is a sample MFC application (VS2008 project) with source code:

Note that I used std::wstring to store the (Unicode) strings in the STL
containers, but you can use CString as well.

A sample portion of code follows:


// *** TEST ***

std::wstring BuildTestString(size_t i)
   std::wostringstream os;
   os << L"This is string #" << i;
   return os.str();

std::wstring BuildTestStringInMap(size_t i)
   std::wostringstream os;
   os << L"String in map #" << i;
   return os.str();

void CTestBigArrayDlg::OnBnClickedButtonTest1()
   typedef std::vector< std::wstring > StringArray;
   typedef std::map< std::wstring, std::wstring > MapStringToString;

   StringArray array;
   MapStringToString map;

   // Number of items
   // size_t count = 10; // <<-- fast test
   size_t count = 4000000;

   // Fill the array
   for (size_t i = 0; i < count; i++)
       array.push_back( BuildTestString(i) );

   // Fill the map
   for (size_t i = 0; i < array.size(); i++ )
       std::wstring key = array[i];
       std::wstring value = BuildTestStringInMap(i);

       // Build association between strings, and store it in map
       map[ key ] = value;

   ASSERT( map.size() == array.size() );

   // Verification loop
   for (size_t i = 0; i < array.size(); i++ )
       std::wstring value = BuildTestStringInMap(i);
       std::wstring key = array[i];

       if ( map[ key ] != value )

           std::wostringstream os;
           os << L"Failed check at position " << i;
           AfxMessageBox( os.str().c_str(), MB_OK|MB_ICONERROR);
   AfxMessageBox( L"All right.", MB_OK );


If you may want to post a compilable sample code of yours, we could try to
give you better help.


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