C / C++ / MFC

23-Mar-05 9:45

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"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

Hardware list error

brilliant10123-Mar-05 8:10

brilliant101

23-Mar-05 8:10

It is the code from MSDN
It complies and links but does not executes giving the following error
File:i386\chkesp.c
line:48
The value of ESP was not properly saved across a fuction call.This is usually a result of calling function decleared with one calling convention with a funciton pointer decleared with a different calling convention.

#include <windows.h>
#include <setupapi.h>
#include <stdio.h>

DWORD Err;

HDEVINFO DoDeviceEnum( GUID InterfaceClassGuid)
/*
Routine Description:
Retrieves the device information set that contains that contains
the devices of the specified class.

Parameters:
InterfaceClassGuid - The interface class GUID.

Return Value:
If the function succeeds, the return value is a handle to the
device information set.

If the function fails, the return value is zero.
*/
{
HDEVINFO DeviceInfoSet;
HDEVINFO NewDeviceInfoSet;

// Create a device information set that will be the container for
// the device interfaces.

DeviceInfoSet = SetupDiCreateDeviceInfoList(NULL, NULL);

if(DeviceInfoSet == INVALID_HANDLE_VALUE) {
Err = GetLastError();
printf( "SetupDiCreateDeviceInfoList failed: %lx.\n", Err );
return 0;
}

// Retrieve the device information set for the interface class.

NewDeviceInfoSet = SetupDiGetClassDevsEx(

&InterfaceClassGuid, // address of guid required

NULL, // no enumerator

NULL, // no parent window handle (might not be a good idea…)

DIGCF_PRESENT | DIGCF_DEVICEINTERFACE, // flags

//DeviceInfoSet, // do not pass this in, not in function prototype

NULL, // NULL implies local machine

NULL // Reserved’ must be null

);

if(NewDeviceInfoSet == INVALID_HANDLE_VALUE)
{
Err = GetLastError();
printf( "SetupDiGetClassDevsEx failed: %lx.\n", Err );
return 0;
}

return NewDeviceInfoSet;
}

int main(int argc, TCHAR* argv[])
{

GUID var;
DoDeviceEnum(var);

return 0;

}

Re: Hardware list error

David Crow23-Mar-05 9:47

Help me debug MFC app that uses COM

23-Mar-05 9:47

Put a breakpoint on the SetupDiCreateDeviceInfoList() statement and single-step through the code until you get to the statement that causes the error.

I cleaned up your code a bit to look like:

HDEVINFO DoDeviceEnum( void )
{
    GUID        InterfaceClassGuid;
    HDEVINFO    DeviceInfoSet,
                NewDeviceInfoSet;
 
    DeviceInfoSet = SetupDiCreateDeviceInfoList(&InterfaceClassGuid, NULL);
    if (DeviceInfoSet != INVALID_HANDLE_VALUE) 
    {
        NewDeviceInfoSet = SetupDiGetClassDevsEx(&InterfaceClassGuid, 
                                                 NULL, 
                                                 NULL, 
                                                 DIGCF_PRESENT | DIGCF_DEVICEINTERFACE, 
                                                 DeviceInfoSet, 
                                                 NULL,
                                                 NULL);
 
        if (NewDeviceInfoSet != INVALID_HANDLE_VALUE) 
            ; // do something with the list
        else
            printf("SetupDiGetClassDevsEx failed: %lu.\n", GetLastError());
 
        SetupDiDestroyDeviceInfoList(DeviceInfoSet);
    }
    else
        printf("SetupDiCreateDeviceInfoList failed: %lu.\n", GetLastError());
 
    return NewDeviceInfoSet;
}
 
void main( void )
{
    DoDeviceEnum();
}

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

Socket programming

vinsankar23-Mar-05 6:55

vinsankar

23-Mar-05 6:55

I had created a structure with six members of type CString.
I am trying to send this structure using the 'Send' command.
A Pointer object is created for the structure.
At the receiving end i had created the same structure. But when i was trying to display the data , I got only a blank message box.

Can anyone solve this problem?

source prg
..........

Struct message
{
CString name;
...
};

message *obj=new message();
Send(obj,sizeof(struct message));

dest prog
........

Struct message
{
CString name;
...
};

message *obj=new message();

Receive(obj,sizeof(struct message));

MessageBox(obj->name); //blank message box was displayed ?

vinsankar

Re: Socket programming

greba23-Mar-05 7:44

greba

23-Mar-05 7:44

The problem with your code is that sizeof(struct message) is going to return the same number no matter what the size of the string. That is because the CString class has a pointer to a buffer which contains the actual string. You have just stumbled upon a problem that occurs very often. There are many ways around this, but the simpliest one I can think of would be to change your struct to:

<br />
struct message<br />
{<br />
  char name[256];<br />
};<br />

sizeof(struct message) would then return 256. This method is inefficient, as the whole buffer would be transferred, and it would be tougher to work with the char arrays instead of the CString's.

Greba,

My lack of content on my home page should be entertaining.

Re: Socket programming

vinsankar23-Mar-05 21:44

vinsankar

23-Mar-05 21:44

why can't we use CString instead of character arrays ?

I am in need of CString values at the receving end.Because I
have to perform some trimming operations at the receiving side.

What is the real problem while displaying the values stored in structure?

Is there any other way to send a structure through the 'Send' command?

vinsankar

Budric B.23-Mar-05 6:18

Budric B.

23-Mar-05 6:18

Hi,
I'm having trouble with using a particular COM object in an MFC application. Here's what happens. I create a brand new MFC application put some code in the message handler to initialize COM, create object, set some properties on the object etc. That works fine. However when I try the exact same code inside another, bigger application the code doesn't work.

First CoInitialize() returns RPC_E_CHANGED_MODE. I have no idea why because this is the first time I call it in the code. I use many other libraries it may be possible that some other library has initialize it. I can either ignore this returned value or put CoInitialize and other code into a thread, in either case problem 2 occurs.

Second, the program doesn't behave as it should. I try to debug it by stepping through the code. CoCreateInstance() works fine, then I set some options on this created instance, that works fine. Then I call another function and MSVC++ displays "First-chance exception...(NTDLL.DLL): Invalid Handle" and I can't debug any further.

How can I debug this? This particular code is identical between the two applications. Both applications seem to have the same project settings. I'm just out of ideas.

CString class

ddmcr23-Mar-05 6:13

ddmcr

23-Mar-05 6:13

Does anybody know how many symbols maximum, a CString object can contain ?

Thanks in advance

Giorgi Moniava

Budric B.23-Mar-05 6:32

Budric B.

23-Mar-05 6:32

The amount of memory your program gets should be the limit of CString size.

David Crow23-Mar-05 7:56

23-Mar-05 7:56

Take a look at CString::AllocBuffer(). You'll notice that it is INT_MAX.

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

toxcct23-Mar-05 8:37

toxcct

23-Mar-05 8:37

the index of a CString object is an int. could you find the size now ?

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Michael Dunn23-Mar-05 14:23

Michael Dunn

23-Mar-05 14:23

The theoretical limit is INT_MAX, or 2GB. But since the buffer has to be contiguous block of memory, and you won't be able to allocate a 2GB block in your process space, the practical limit is much less.

--Mike--
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Strange things are afoot at the U+004B U+20DD

Events in MFC...

anderslundsgard23-Mar-05 5:06

anderslundsgard

23-Mar-05 5:06

I wonder how to send and catch events in MFC. I’m well known how a CWnd is catching an “regular” winows envent but if I like to catch an event from:

class A { … }
to
class B { … }

?

_____________________________

...and justice for all

APe

David Crow23-Mar-05 5:39

23-Mar-05 5:39

Have you searched MSDN for TRY, CATCH(), and THROW()?

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

anderslundsgard23-Mar-05 7:51

anderslundsgard

23-Mar-05 7:51

For me that is about Exception handling...

_____________________________

...and justice for all

APe

David Crow23-Mar-05 7:54

23-Mar-05 7:54

My bad. What exactly do you mean by "events?"

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

Maximilien23-Mar-05 8:10

Maximilien

23-Mar-05 8:10

depending on the relation between A and B there are numerous ways of "catching" events ...

if A and B know each other ( i.e. A includes a pointer/reference to B, or vice-versa ), you can directly call methods from A to B ( or vice-versa )

if A and B do not know each other ( or you don't want to make them know each other ), you can make them inherit from CCmdTarget and use SendMessage/PostMessage and handle your user message in each class

if you don't want to have a dependency on MFC/Win32, you could use one form of the Observer Pattern to register each class as either observer or observable to send message between them.

Maximilien Lincourt
Your Head A Splode - Strong Bad

anderslundsgard23-Mar-05 9:39

anderslundsgard

23-Mar-05 9:39

Maximilien wrote:
if A and B do not know each other ( or you don't want to make them know each other ), you can make them inherit from CCmdTarget and use SendMessage/PostMessage and handle your user message in each class

-> Thats what I want!

I've successfuly "cached" a SendMessage(...) in a CWnd derived class but I don't get it to work between two generic (my own created classes). Really glad for an Articel in this subject, but have not found any here at CP...

_____________________________

...and justice for all

APe