C / C++ / MFC Discussion Boards

p_26-Jul-07 23:33

26-Jul-07 23:33

yes sir i think u r right call is failing
becauze when debugger comes on if(res) it will show login window again
and this will stop debugger
but i dont know sir why this if(mysql_query(myDB,"select * from login"))
is not fetching result

[sir i use mysql 6.0 and VC++ 6.0(is there any problem Sir)]

Re: Access Violation problem

Jonathan [Darka]26-Jul-07 23:37

Jonathan [Darka]

26-Jul-07 23:37

Are there any records in the database table ?

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_26-Jul-07 23:47

26-Jul-07 23:47

yes sir
i have database gourav , a table login and
this table has three fields user , password and id
and there are three records in this table

Re: Access Violation problem

Jonathan [Darka]27-Jul-07 0:02

Jonathan [Darka]

27-Jul-07 0:02

What is the return value from the mysql_query(myDB,"select * from login")) function ?

Change it to this for a test:

int i = mysql_query(myDB,"select * from login");

What is the value of i ?

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_27-Jul-07 0:09

27-Jul-07 0:09

sir return value for
int i = mysql_query(myDB,"select * from login");
and i shows value 1 when use debugger

Re: Access Violation problem

Jonathan [Darka]27-Jul-07 0:24

Jonathan [Darka]

27-Jul-07 0:24

Add the try/catch block that Shouvik suggested, it should help diagnose the problem.

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_27-Jul-07 0:40

27-Jul-07 0:40

thanks a lot sir
u have devoted a lot of time for me
thanks a lot

Re: Access Violation problem

Jonathan [Darka]27-Jul-07 0:41

Jonathan [Darka]

27-Jul-07 0:41

No problem, just trying to help a fellow coder.

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

Shouvik Das27-Jul-07 0:06

Shouvik Das

27-Jul-07 0:06

Surround the code for retrieving with a try and catch. then get the error reason by catching the Exception object throught the method what();

I think Jonathan is right. The recordset value is NULL and hence throws an Acess Violation Error

There are only two kinds of people who are really fascinating-people who know absolutely everything, and people who know absolutely nothing.
Oscar Wilde (1854-1900)
Regards...
Shouvik

Re: Access Violation problem

p_27-Jul-07 0:35

27-Jul-07 0:35

sir thnaks
but i dont know about the what(); function
so can u help me sir
thanks

Re: Access Violation problem

Shouvik Das27-Jul-07 0:45

Shouvik Das

27-Jul-07 0:45

Actually I'm not well versed with ODBC section in VC 6.0 So I m just givin u a generalized concept.
Whenever you surround any code with try catch you throw an exception which is the Object of CException Class.

try
{
//Ur record retrieval code goes here

//On error u write a logic to throw an exception object

}
catch(CException e)
{
 MessageBox(e.what()); // will contain the error message
}

So this way you can atleast trace what error are u getting.

There are only two kinds of people who are really fascinating-people who know absolutely everything, and people who know absolutely nothing.
Oscar Wilde (1854-1900)
Regards...
Shouvik

Re: Access Violation problem

p_27-Jul-07 1:06

27-Jul-07 1:06

sir what() is not working with this
it will give error
'what' : is not a member of 'CException'
please sir solve this
thanks

Re: Access Violation problem

Jonathan [Darka]27-Jul-07 1:07

Jonathan [Darka]

27-Jul-07 1:07

Change the code to this:

int i;
MYSQL *myDB = NULL;
MYSQL_RES *res = NULL;
MYSQL_ROW row;
CString user,pass,aqp;

try
{
    if((myDB = mysql_init((MYSQL*) 0)) &&
    mysql_real_connect(myDB,"localhost","root",NULL,NULL,3306,NULL,NULL))
    {
        if(mysql_select_db( myDB,"gourav"))
        {
            GetDlgItemText(IDC_USER,user);
            GetDlgItemText(IDC_PASS,pass);

            if(mysql_query(myDB,"select * from login"))
            {
                res=mysql_store_result(myDB);
                if(res)
                {
                    row = mysql_fetch_row(res);
                    if(row != FALSE)
                        MessageBox(row[0]);
                }
            }
        }
        else
            MessageBox("Can't connect !\nPlease try later.") ;

        mysql_close(myDB);
}
catch(CException& e)
{
    MessageBox(e.what()); // will contain the error message
}

do you get a messagebox with a description of the error in it ?

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_27-Jul-07 1:18

27-Jul-07 1:18

no messagebox sir
because what() is not working with this
it will give error
'what' : is not a member of 'CException'
thanks

Re: Access Violation problem

Jonathan [Darka]27-Jul-07 1:25

Jonathan [Darka]

27-Jul-07 1:25

Change what() to ReportError()

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_27-Jul-07 1:40

27-Jul-07 1:40

hi try this
catch(CException& e)
{
MessageBox(e.ReportError());
}
but gives this error
'MessageBoxA' : cannot convert parameter 1 from 'int' to 'const char *'

Re: Access Violation problem

Shouvik Das27-Jul-07 1:43

Shouvik Das

27-Jul-07 1:43

you will find in my previous post how to get the error into the char err[255].

now pass this as

MessageBox(err);

I hope this works for you fine now

There are only two kinds of people who are really fascinating-people who know absolutely everything, and people who know absolutely nothing.
Oscar Wilde (1854-1900)
Regards...
Shouvik

<font colour=orange>Re: Access Violation problem</font>

Shouvik Das27-Jul-07 1:38

Shouvik Das

27-Jul-07 1:38

virtual BOOL GetErrorMessage(LPTSTR lpszError,UINT nMaxError,PUINT pnHelpContext = NULL);

Sorry if it is not working. use the above function...the lpszError will containt the error message.

you can have the a

char err[255];
exp_obj.GetErrorMessage(err,255);

hope u get my point

There are only two kinds of people who are really fascinating-people who know absolutely everything, and people who know absolutely nothing.
Oscar Wilde (1854-1900)
Regards...
Shouvik

Debug Assertion error

Anu_Bala26-Jul-07 18:21

Anu_Bala

26-Jul-07 18:21

I got assertion error when im starting the application. it show me the error at Application class(GUSapp.cpp)
CMainFrame* pMainFrame = new CMainFrame;
if (!pMainFrame->LoadFrame(IDR_MAINFRAME))
Whe i debug it,particularly the error occurs at the line
int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
if (CMDIFrameWnd::OnCreate(lpCreateStruct) == -1)

At this line assertion error occurs and it debug library shows File:Winmdi.cpp,Line:139.

Why this error occur? My applcation is MDI application and im working in MFC.

Anu

Re: Debug Assertion error

Roger Broomfield26-Jul-07 20:15

Roger Broomfield

26-Jul-07 20:15

The short answer is: because your menu doesnt have enough items in it.

CMDIFrameWnd::OnCreate() attempts to guess which sub-menu is the Window menu. It does this based on the assumption that you have followed the Windows user interface guidelines and have a Help menu as the right-most item and a Window menu immediately to the left of that. The assertion you are getting is specifically because the menu you have made for IDR_MAINFRAME has less than 2 items.

Re: Debug Assertion error

Anu_Bala26-Jul-07 21:10

Anu_Bala

26-Jul-07 21:10

OK. But i need only one menu for my application and specially i dont want help menu and file,view etc.,
I added a one new menu in IDR_MAINFRAME as Operator Station,thats all. This is enough for me.
IS there anyway to overcome this error?

Anu

Re: Debug Assertion error

Roger Broomfield26-Jul-07 22:19

Roger Broomfield

26-Jul-07 22:19

I think before anything else you should read and understand all the functionality of CMDIFrameWnd Class[^] and perhaps review the Win32 MDI documentation[^]

Then you might replace your OnCreateClient with this

BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT lpcs, CCreateContext* pContext) <br />
{<br />
 CMenu* pMenu = NULL;<br />
 if (m_hMenuDefault == NULL)<br />
 {<br />
  pMenu = GetMenu();<br />
  ASSERT(pMenu != NULL);<br />
  pMenu = pMenu->GetSubMenu(0);<br />
  ASSERT(pMenu != NULL);<br />
 }<br />
<br />
 return CreateClient(lpcs, pMenu);<br />
}

That will append the window list to your single Operator Station menu, you might also need to override other member functions of CMDIFrameWnd such as GetWindowMenuPopup which expects to find a standard window menu.

Alternately you could add a standard Window menu after Operator Station and replace your OnCreateClient with this

BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT lpcs, CCreateContext* pContext) <br />
{<br />
 CMenu* pMenu = NULL;<br />
 if (m_hMenuDefault == NULL)<br />
 {<br />
  pMenu = GetMenu();<br />
  ASSERT(pMenu != NULL);<br />
  pMenu = pMenu->GetSubMenu(1);<br />
  ASSERT(pMenu != NULL);<br />
 }<br />
<br />
 return CreateClient(lpcs, pMenu);<br />
}

this is the way I would do it, if I really had to leave out the help menu, as it reduces the number of member functions that you might have to override.

Personally I would include the standard Window menu and a simple Help menu with just an about box.

Re: Debug Assertion error

Anu_Bala26-Jul-07 23:10

Anu_Bala

26-Jul-07 23:10

Yes, It works.I includeed OnCreateClient() and it works fine.

Anu

Re: Debug Assertion error

Anu_Bala26-Jul-07 23:18

Anu_Bala

26-Jul-07 23:18

It works fine. But i cannot close,minimize,maximize the mainframe as well as child window.Even i have buttons for all this.
Whats the problem in that?Pls help me.

Anu

Re: Debug Assertion error

Roger Broomfield26-Jul-07 23:35

Roger Broomfield

26-Jul-07 23:35

Not sure where to start with this. Do you get any messages in the Output window when you debug the application and try to close,minimize,maximize the mainframe or child windows ?

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.