ATL / WTL / STL

Re: ATL how get the name of the target class inside of a template?

12-Feb-13 4:55

Take a look at the template specifications[^].

Frank Thielemann15-Feb-13 19:51

Frank Thielemann

15-Feb-13 19:51

hm this doesnt help me...
can you please just answer the question if you know it
thanks Frank

add sys dsn failed on windows 7 64

MrKBA11-Feb-13 5:59

MrKBA

11-Feb-13 5:59

I try to create sys dsn from my C++ application
but i have always the same error:

The installation routines ODBC Microsoft Access Driver (*. Mdb) are not found. Please reinstall the driver.

I have Office 2007 installed but always error

For example this a VB test which return failed:

Public Class Form1
    Private Declare Function SQLConfigDataSource Lib "ODBCCP32.DLL" (ByVal hwndParent As Integer, ByVal ByValfRequest As Integer, ByVal lpszDriver As String, ByVal lpszAttributes As String) As Integer
    Private Const ODBC_ADD_SYS_DSN As Short = 4
    Private Const vbAPINull As Integer = 0 ' NULL Pointer

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        CreateSystemDSN()

    End Sub
    Public Sub CreateSystemDSN()
        Dim ReturnValue As Integer
        Dim Driver As String
        Dim Attributes As String
        Driver = "Microsoft Access Driver (*.mdb)"
        Attributes = "SERVER=SomeServer" & Chr(0)
        Attributes = Attributes & "DESCRIPTION=New DSN" & Chr(0)
        Attributes = Attributes & "DSN=DSN_TEMP" & Chr(0)
        Attributes = Attributes & "DATABASE=pubs" & Chr(0)
        ReturnValue = SQLConfigDataSource(vbAPINull, ODBC_ADD_SYS_DSN, Driver, Attributes)
        If ReturnValue <> 0 Then
            MsgBox("DSN Created")
        Else
            MsgBox("Create Failed")
        End If
    End Sub
End Class

Thank you.

SQL Server Compact Edition

Haakon S.11-Feb-13 4:23

Haakon S.

11-Feb-13 4:23

I have just gone from Visual C++ 6.0 to Visual Studio 2012. So far it is working well, I have manged to transfer my application over, albeit with some difficulties. But the program creates this big SQL Server Compact Edition, which I don't need. My application is not a database tool. How do I remove it?

Re: SQL Server Compact Edition

Richard MacCutchan11-Feb-13 4:42

Re: SQL Server Compact Edition

11-Feb-13 4:42

How does it create this unless you have added it to the project?

Haakon S.11-Feb-13 5:37

Haakon S.

11-Feb-13 5:37

Richard MacCutchan wrote:

How does it create this unless you have added it
to the project?

Well, I haven't. The file is totally new to me. It just pops up.

Re: SQL Server Compact Edition

Richard MacCutchan11-Feb-13 5:58

error while trying to uplaod the file in current directory using c language

11-Feb-13 5:58

I assume then that you are talking about the file with the same name as the solution. This is created and used by Visual Studio that contains information about the solution and it's references.

raghvendrapanda30-Jan-13 19:34

raghvendrapanda

30-Jan-13 19:34

Hi,
i writing a code in c language in load runner to upload a file into the current directory using c.I am getting an error
"operands of = have illegal types `pointer to char' and `int'"

Below is my code:-

char *current_dir = getcwd();
char *filename = "current_dir:\\EUR_PR_01302013.txt";
long file_stream;
if ((file_stream = fopen(filename, "a+")) == NULL) //open file in append mode
{
lr_output_message("Unable to create %s", filename);
return -1;
}

Any kind of help/suggestion will be appreciated.

regards,
raghvendra panda

Re: error while trying to uplaod the file in current directory using c language

Richard MacCutchan30-Jan-13 22:03

Re: error while trying to uplaod the file in current directory using c language

30-Jan-13 22:03

Which line gives the error?
And please use <pre> tags around your code.

«_Superman_»1-Feb-13 20:34

«_Superman_»

1-Feb-13 20:34

You have to format the filename string.
Also need to allocate memory to it.

char filename[1024];
sprintf(filename, "%s\\EUR_PR_01302013.txt", current_dir);

«_Superman_»
I love work. It gives me something to do between weekends.

Microsoft MVP (Visual C++) (October 2009 - September 2013)

Polymorphism in C

TCP/IP CAsyncSocket and pointers to same

bkelly1324-Jan-13 15:16

classes don't call upwards

24-Jan-13 15:16

Environment Windows XP and 7, Visual Studio 2008, C++.
Experience level: novice with TCP/IP, but do have the application working with CAsyncSocket.

The message application receives telemetry data from some hardware (arrives fast and furious), processes it and dispatches the results to a display device via TCP/IP. It sends the data to the client but does not receive from the client.

Setup: the TCP “Manager” is started by the main application and it listens for the client. On connect, it creates the “Sender” that does all the sending.

Question: what is the best, read that simple and maintainable, way for the manager to get the Sender pointer to the main application so it can use the Sender? When the client closes the connection, how is the application informed of that?

Tentative proposal: the application provides the Manager with a pointer to itself. When the connect is made the Manager calls an application method such as
Set_TCP_Sender_Pointer( C_Sender_Class *new_sender_pointer );

The Manager can pass the pointer (to the main application) to the Sender on creation. When the Sender gets a close from the client, it calls the same method using a NULL for the argument. This makes the application aware there is no Sender. Then the Sender exits. (There is only one thread so I think there is no concern about the application using a pointer to a non-existent Sender.)

I am pretty sure that will work, but if you had to pick up on this project, would it be easy to understand and maintain? Presume you are not an expert with TCP/IP in the Microsoft world.
I am open to alternative suggestions.

Thanks for your time

bkelly1326-Jan-13 8:55

26-Jan-13 8:55

After writing the OP I outlined the process with all the steps then began to implement.

I have started using a common directory for re-usable code. In order for the Manager to call a method in its creator it must know the name of the owner's class. To do that I added a forward declaration in the Manager.

However, this means that when the class is re-used, and the owner has a different name, the Manager must be changed.

There is another indicator this is a bad practice. After the forward declaration in the dot H file, the dot CPP file needs to reference the dot H file of the owner. The common code resides in another directory and it cannot find the central code of the main project unless it is specifically spelled out. Then, if the project is moved or re-name, the common code must change.

There may be a way to do this automatically using directive and path names within Visual Studio. But I now think that even if that can be done it would be miss-guided.

Conclusion:
A utility class can call "down" the heiarchy to objects it creates, but should not call up to its owner. While the concept of it calling up may make the owner code neater, it represents an inversion of authority. (Regardless of how the methods are name, a call up in an inversion.)

Problems remain:
The main application uses pointers into the lower level objects to accomplish its tasks. How does it become aware that the lower level needs to exit, or maybe even has already exited.

Controlled exits:
When the TCP sending function detects that the client has closed the connection it does not exit right away. It waits until the upper level code calls the method to send the data. Then the lower level returns an error code stating that the data has not been sent and that the object is exiting.

Uncontrolled exits:
I generally do not like exceptions, but this appears to be a time when an exception is warranted. When the lower level must terminate unexpectedly, then an exception could work its way back to the upper level and the exception handler can NULL the pointer.

Thanks for your time

ATL and exceptions

imagiro14-Jan-13 8:10

imagiro

14-Jan-13 8:10

I personally never used exceptions for ATL projects. Now a colleague votes strongly for throwing exceptions instead of returning HRESULTs. I did some research, and even here on codeproject I don't find much about ATL and exceptions. To me it appears that exceptions in ATL are not very popular. So I would like to know from you ATL guys:

Do you use exceptions? Or you simply return an HRESULT?

And most imporant: Why?

Cheers
Imagiro

Jonathan Davies18-Jan-13 9:39

Jonathan Davies

18-Jan-13 9:39

I used a combination. A colleague and I developed an exception object with various constructors that could, for example, be thrown with parameters of: a HRESULT, a string describing what failed, the file name it was thrown in, and the line number of the file it was thrown in.

for example:

C++

HRESULT hr = somefunc();
if(FAILED(hr))
{
    throw _abc_error(hr, L"Somefunc failed", FILE_AND_LINENO);
}
...
catch(_abc_error& err)
{
    MessageBox(err.ErrorMessage(), L"App Name", MB_ICONWARNING | MB_OK);
}

The exception object constructor then took care of writing the error as an event to the System Event log as well as looking up any messages from the HRESULT, or accessing any other error handling mechanism needed.
This resulted in code unclutered with complicated error handling and a standard way of making sure that the log showed not only an error code or message, but a comment on what was being attemted, which .cpp file this was detected in and the line number of the file.

Jonathan

bkelly1324-Jan-13 15:24

24-Jan-13 15:24

Personally: I never did like exceptions and avoid them. I did a google on "exceptions C++ pros and cons" and found several discussions. There are some strong opinions on this.

I would much rather test for bad conditions and return an error code as opposed to throwing an exception.

Thanks for your time

PS: This is a nice discussion:
C++ Exceptions: Pros and Cons[^]

Jonathan Davies6-Feb-13 7:23

Jonathan Davies

6-Feb-13 7:23

I agree when you say you'd rather return an error code than throw an exception. I found using exceptions locally makes the code clearer and imposes some structure. Having caught the exception locally and dealt with it i.e. usually recorded what exactly went wrong etc I too then prefered to return an error code.

Jonathan

Albert Holguin11-Feb-13 5:12

Albert Holguin

11-Feb-13 5:12

Having originally started with C, I too prefer returning an error code to be cleaner than catching exceptions, but I'm sure others see exceptions as the true C++ method for handling errors.

unicode and non-unicode

bkelly1314-Jan-13 3:45

14-Jan-13 3:45

Windows XP and 7, Visual Studio 2008 and 2010, MFC, C++

Application A supports Unicode and application B does not. Class Log_Writer does not support Unicode. Both applications use Log_Writer ok passing a char * to log writer.

The problem is within Log_Writer when it cannot open the log file. It uses AfxMessageBox() to display an error to the user. When Log_Writer is compiled within the A environment the error message is:
None of the 2 overloads could convert all the argument types.
What can be done so that Log_Writer will work in both environments?

Thanks for your time

Richard MacCutchan14-Jan-13 6:24

14-Jan-13 6:24

What is that actual code where the error is given?

One of these days I'm going to think of a really clever signature.

bkelly1314-Jan-13 8:43

14-Jan-13 8:43

the code is

AfxMessageBox("Unable to open log file");

If I pass it a CString it is okay as in:
CString x;
x.Format( L"stuff" );
AfxMessageBox( x );

But that does not compile in the non unicode project. I am hoping for something that will compile in both worlds.

EDIT: It finally occurred to me that there might a a define for unicode,..., and there is. A bit of googling showed me that using a #ifdef _UNICODE etc will resolve the problem.

Still, is there a way to write the code that will compile in both worlds?

Thanks for your time

modified 14-Jan-13 15:03pm.

Richard MacCutchan14-Jan-13 22:13

14-Jan-13 22:13

C++

x.Format( L"stuff" );

is wrong for ASCII based compiles, since the L prefix generates a Unicode string. Use the _T() macro around all your string and character constants and they will be correctly generated as ASCII or Unicode depending on the project settings. Note, do not forget to #include <tchar.h> for the foregoing macro.

One of these days I'm going to think of a really clever signature.

Richard MacCutchan20-Jan-13 22:08

20-Jan-13 22:08

bkelly13 wrote:
EDIT: It finally occurred to me that there might a a define for unicode,..., and there is. A bit of googling showed me that using a #ifdef _UNICODE etc will resolve the problem.

You should use the Project Properties -> General -> Character Set, to select Unicode or ASCCII for your project.

pasztorpisti20-Jan-13 1:33

pasztorpisti

20-Jan-13 1:33

If you are writing code for windows NT and not for Win9x and its friends then forget about the A version of your program and simply stop maintaining it. This results in much less trouble for programmers, cleaner easier to read code. Actually WinNT uses utf16 internally so all A functions are just functions that do string conversions before and/or after calling a W version. Win9x is almost dead and the same is true for the A version of programs that is simply a heritage from old times.

bkelly1320-Jan-13 8:56