Got It! Thanks (Again)

billyard <>
Fri, 28 Dec 2007 13:36:03 -0500
billyard wrote:

If I don't execute the LocalFree functions - memory leak.

If I do execute ALL the LocalFree functions - program dies.

Without my "LocalFree" problems - the program works perfectly.

I know I'm doing something stupid. There is some extraneous code in here
that is due to my testing. I left it in. Once again, Thank you in advance!

Here's the code.

CString CChildView::DecryptPOP3Password(BYTE* ppData, DWORD pBytes)
   // Get the hard drive's serial number - used for encryption purposes.
   CHardDriveInfo hardDriveInfo;
   CString strPassword;

   DATA_BLOB DataEntropy;
   DATA_BLOB DataOut;
   DATA_BLOB EncData;

   LPWSTR description;

   DataEntropy.pbData = (BYTE*)hardDriveInfo.HardDriveSerialNumber;
   DataEntropy.cbData = (DWORD)strlen((char*)

   EncData.cbData = pBytes;
   EncData.pbData = ppData;

   strPassword = DataOut.pbData;
   HLOCAL MyLocalMemory;
   DWORD LastError;
   MyLocalMemory = LocalFree(description); // This works fine
   if (NULL != MyLocalMemory)
      LastError = GetLastError();

   MyLocalMemory = LocalFree(DataOut.pbData); // This works fine
   if (NULL != MyLocalMemory)
      LastError = GetLastError();

   MyLocalMemory = LocalFree(&hardDriveInfo); // DOESN'T WORK
   if (NULL != MyLocalMemory)
      LastError = GetLastError();
      TRACE1("failed with error %d", LastError);
   MyLocalMemory = LocalFree(EncData.pbData); // THIS FAILS - CORRUPT
                                                 // HEAP - STOPS PROGRAM

   MyLocalMemory = LocalFree(DataEntropy.pbData);
   if (NULL != MyLocalMemory)
      LastError = GetLastError();
      TRACE1("failed with error %d", LastError);
   return strPassword;

Ok. Here's what was going on. Running in Debug mode, I would get an
error telling me about a Memory Leak. I wrote down the address of the
leak. It was the same every time I ran the program. Then I started
checking the address of the variables in my program. When I discovered
the address was the same address as EncData.pbData from above, I tried
using the LocalFree function thinking (or more precisely - not thinking)
that would take care of it. When that gave me an error, I added some
other LocalFree functions to see if they would work. Some did, some did
not. Thanks to Daniel And Joe, I now know why. So...

Before I got out of bed this morning, it occurred to me that the address
of EncData.pbData was determined in the calling routine. Duh. Sort of
can't see the forest for the trees, I guess. So, I added a Free()
function there and removed all the unnecessary LocalFree() functions and
all is well!

Thanks for the help all!

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