Re: Debug Assertion Failure

Sat, 16 Jun 2007 01:21:55 -0700
On Jun 16, 11:01 am, MrAsm <> wrote:

On Sat, 16 Jun 2007 00:15:50 -0700, wrote:

I've isolated the problem to the following statement:


Whenever I remove that line from the function, the error doesn't pop;
therefore it's probably something in that function.


What is your goal?
Are you going to "raw-copy" the 'CUser_IO temp_user' from file?
I would read/write structure bytes to file *only* if it is a plain
simple C structure, e.g.

  struct User
     TCHAR Name[MAX_NAME];
     unsigned int Zip;
     TCHAR Address[MAX_ADDRESS];

  User anUser;
  ExampleWriteToFile( &anUser, sizeof(anUser) );

Even if you have a member like a CString or a pointer to something, I
would *not* read/write structure to file just copying its raw bytes;
in these cases a finer serialization mechanics is required.

What is the definition of CUser_IO ? Is it a plain C structure?

If you want to read/write complex data to file, you might consider
serializing using XML (very widespread today! and easy to debug
because it's a text format, not a binary format), or using MFC
CArchive, ...or something from Boost, or *carefully* write your own
serialization system.

bool CFileHandler::ReadFromFile (char* ptr, long offset)


   memset (ptr, 0, m_BlockSize);

Is m_BlockSize == sizeof(CUser_IO)?
You're clearing memory, you must be sure that you are not touching
bytes out-of-boundaries; this may cause memory corruption., ios::in | ios::binary);

   if (in_file.is_open())
                           in_file.seekg(offset + POINTER_SIZE, ios::beg);
         , m_BlockSize);

Again: is 'm_BlockSize == sizeof(CUser_IO)' ?

Is 'offset' consistent with your binary file format?
(I don't know what is your binary file format that you are using

Another option I thought of is that the stack could simply run out of
space (I've looked at the call stack, and it has depth of around 12
levels). Could this be what causes the problems?

...I'm much more suspicious about the way you are reading (and maybe
elsewhere writing) data from binary file, the way you are clearing
memory with memset and using m_BlockSize...


Here is CUser_IO's definition:

class CUser_IO
    string UserName;
    string Password;
    long ID;
    E_Clearance Clearance;

The file only reads and writes CUser_IOs, and m_BlockSize is
initialized to sizeof(CUser_IO) through the constructor. I believe
CUser_IO qualifies as a simple class; and I've tested the CFileHandler
class as a stand-alone module, and encountered no problems. The
problem only appears when I integrate it with the MFC interface.

Offset is consistent with the binary format; all the read/write
functions work using the same format, and offset is always returned by
one of them.

Regarding serializing using XML or another mechanism, I'd gladly do
that, but that would be against the project's definition (it's a
university project).

Again, I've tested the CFileHandler class before integrating it with
the MFC, and it worked smoothly; I've read, written and deleted data
from the file over and over again, and the output always came out

Any ideas?

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