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Re: LPCTSTR and HRESULT

Shouvik Das29-Jul-07 19:22

29-Jul-07 19:22

George_George wrote:
Thanks for your support for all the help you given to me on the question all the way.

That is the spirit @ CP and that is what makes my day happier while spending my day here. We all come back for a reason.

Actually one more thing to say is that LPCTSTR is strictly a Win32 stuff so please investigate it's memory implications then only proceed.In case you get to know some APIs which are translating 32 to 64 bit please share with us too.

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: LPCTSTR and HRESULT

Shouvik Das29-Jul-07 19:31

29-Jul-07 19:31

throwing some more light
http://www.codeproject.com/script/comments/forums.asp?msg=2153729&forumid=1647#xx2153729xx[^]

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: LPCTSTR and HRESULT

George_George29-Jul-07 19:46

29-Jul-07 19:46

Thanks, good link!

regards,
George

Access Violation problem

p_26-Jul-07 18:23

26-Jul-07 18:23

please tell me
what this problem means in connection of vc++ and mysql
inhandled exception myprojectname.exe(LIBMYSQL.DLL) 0xC0000005: Access Violation

please help me to solve this problem

thanks Rose | [Rose]

Rose | [Rose]

Rose | [Rose]

Rose | [Rose]

Smile | :)

hi

Re: Access Violation problem

Jonathan [Darka]26-Jul-07 20:54

Jonathan [Darka]

26-Jul-07 20:54

It means you have a bug in your code, why not try the debugger ?

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_26-Jul-07 21:08

26-Jul-07 21:08

thanks for reply sir
i use debugger and debugger shows this error in msgbox
and my code is as sir :
int i;
MYSQL *myDB;
MYSQL_RES *res;
MYSQL_ROW row;
CString user,pass,aqp;
if ((myDB = mysql_init((MYSQL*) 0)) &&
mysql_real_connect(myDB,"localhost","root",NULL,NULL,3306,NULL,NULL))

{
if ( mysql_select_db( myDB,"gourav") < 0 )
{
MessageBox("Can't select the database !\nTry later.");
goto exit_here;
}
else
{
MessageBox("Can't connect !\nPlease try later.") ;
goto exit_here;
}
}
GetDlgItemText(IDC_USER,user);
GetDlgItemText(IDC_PASS,pass);
if(mysql_query(myDB,"select * from login"))
res=mysql_store_result(myDB);
row = mysql_fetch_row(res);
MessageBox(row[0]);

exit_here:
mysql_close( myDB);

please sir help me to solve this one
thanks again

hi

Re: Access Violation problem

Jonathan [Darka]26-Jul-07 21:20

Jonathan [Darka]

26-Jul-07 21:20

No problem, does the debugger indicate which line might be cusing the access violation ?

Try changing the code a little as your error handling could be improved, I rewrote it like this, but obviously have not tested it, so give it a go and see if that improves anything.

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

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);
            row = mysql_fetch_row(res);
            MessageBox(row[0]);
        }
    }
    else
        MessageBox("Can't connect !\nPlease try later.") ;

    mysql_close(myDB);
}

regards,

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_26-Jul-07 22:16

26-Jul-07 22:16

thanks sir
sir i try this one but it does not work
as same error at line

row = mysql_fetch_row(res);
before this same error at same line
thanks

hi

Re: Access Violation problem

Jonathan [Darka]26-Jul-07 22:19

Jonathan [Darka]

26-Jul-07 22:19

What is the value of 'res' when this line is executed, you'll need to strp through the code in your debugger.

res=mysql_store_result(myDB);

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

p_26-Jul-07 22:31

26-Jul-07 22:31

sir after debugging :
myDB shows this value 0x00ba4008
and res shows this 0x00000000
thanks.

hi

Re: Access Violation problem

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

Jonathan [Darka]

26-Jul-07 23:07

I suspect the call is failing, have you tried adding mysql_error() to see if you get an error.

Also, change this part of the code:

if(mysql_query(myDB,"select * from login"))
{
    res=mysql_store_result(myDB);
    row = mysql_fetch_row(res);
    MessageBox(row[0]);
}

to this:

<pre
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]);
="" }
}<="" pre="">

Jonathan Wilkes
Darka[Xanya.net]

Re: Access Violation problem

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)]

hi

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

hi

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

hi

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

hi

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

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

hi

Re: Access Violation problem

Shouvik Das27-Jul-07 0:45

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

hi

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

hi

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