Dan G Dan G - 1 year ago 81
C++ Question

AfxMessageBox - Access violation

Here is what is going on. When I try and run an AfxMessageBox from my CDialog extension class, I get an errror (see below). I've googled the internet but come up short. This is the only place the messagebox fails, and I know the rest of the code works (I stepped through it).

Does anyone know how to fix this?

Thanks in advance!

Error message when AFXMESSAGEBOX opens:

Unhandled exception at 0x014b4b70 in IsoPro.exe: 0xC0000005: Access violation reading location 0x34333345.

Code to launch AfxMessageBox, from within CDialog

LPTSTR temp;
CString cstr;
cstr.Format("mainPassword = %s",temp);

Code to display CDialog:

CEnterpriseManagementDialog* emd = new CEnterpriseManagementDialog();

Answer Source

The problem is how you use GetWindowText:

LPTSTR temp;

You are letting GetWindowText attempt to write to some unitialized memory passing temp. If you really want to use a raw output buffer, you should preallocate room for it before passing a pointer to GetWindowText, e.g.:

TCHAR temp[100];
mainPassword.GetWindowText(temp, _countof(temp));
// NOTE: No need to LPTSTR-cast

But, since you are using C++, you may want to just use a string class like CString, instead of raw buffers, e.g.:

CString password;

CString msg;
msg.Format(_T("mainPassword = %s"), password.GetString());
// or you can just concatenate CStrings using operator+ ... 
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