Re: Debug Assertion Failure

From:
MrAsm <mrasm@usa.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
Sat, 16 Jun 2007 08:01:30 GMT
Message-ID:
<t95773he7u6ege72r13nlcb2taqukr84nl@4ax.com>
On Sat, 16 Jun 2007 00:15:50 -0700, katz911@gmail.com wrote:

I've isolated the problem to the following statement:

m_UserFile.ReadFromFile(reinterpret_cast<char*>(&temp_user),iter);

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


hmm...

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.

     in_file.open(m_FileName.c_str(), ios::in | ios::binary);

    if (in_file.is_open())
    {
    in_file.seekg(offset + POINTER_SIZE, ios::beg);
                   in_file.read(ptr, 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
here.)

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...

MrAsm

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