Re: mac desing: - C / C++ / MFC Discussion Boards

Re: DLL with a callback

Richard MacCutchan16-Apr-21 0:17

Richard MacCutchan

16-Apr-21 0:17

CPallini wrote:
a bit confused

I assumed that was just me. Sniff | :^)

Re: DLL with a callback

Bodo240716-Apr-21 3:47

Bodo2407

16-Apr-21 3:47

OK, now I experience another issue with it, I'm sorry.
Hopefully you can help me here as well.

I now want to call the callback function if an timer expires. Therefore I create an timer in a function I call from the main application. I store the handles to the timer and the timer queue globally in static variables.

C++

static HANDLE gDoneEvent;
static HANDLE hTimer = NULL;
static HANDLE hTimerQueue = NULL;
int arg = 123; //will be passed to callback of timer


VOID CALLBACK TimerRoutine(PVOID lpParam, BOOLEAN TimerOrWaitFired)
{
    if (lpParam == NULL)
    {
        //do some error handling her
        return;
    }
    else
    {
        if(s_user_function!=nullptr)
            s_user_function(12);
    }
    //SetEvent(gDoneEvent);   //for periodic calls, don't set gDoneEvent
}

Now, in some function called from the main application, I allocate the timer and start it:

C++

char timer_init(void)
{   
    // Use an event object to track the TimerRoutine execution
    gDoneEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    if (NULL == gDoneEvent)
    {
        return 1;
    }
    // Create the timer queue.
    hTimerQueue = CreateTimerQueue();
    if (NULL == hTimerQueue)
    {
        return 2;
    }
    CreateTimerQueueTimer(&hTimer, hTimerQueue, (WAITORTIMERCALLBACK)TimerRoutine, &arg, 3000, 10000, 0);

    WaitForSingleObject(gDoneEvent, INFINITE); //if we don't wait it crashes although handles are stored globally?
        
    //the handles should be closed and deleted only after timer had occured. 

    ////CloseHandle(gDoneEvent);
    ////// Delete all timers in the timer queue.
    ////if (!DeleteTimerQueue(hTimerQueue))
    ////    printf("DeleteTimerQueue failed (%d)\n", GetLastError());
}

As you can see, I don't close the handles and delete the timer queue on purpose.
Everything works fine as long as the process waits. The callback in the main application is called.
If I comment out the line with WaitForSingleObject I'll get an access exception, although I stored all the handles globally. Teh exception occurs with the timing the timer would have. So most likely it tries to call the callback of the timer function but something is missing.
What is it I'm overlooking?
I need the dll running, not waiting inside a fucntion for a timer...

Re: DLL with a callback

Richard MacCutchan16-Apr-21 4:33

Richard MacCutchan

16-Apr-21 4:33

Bodo2407 wrote:
I need the dll running, not waiting inside a fucntion for a timer..

I am not sure what you mean by that. When you create a timer, it is designed to call some function after a specified period of time, either once or repeatedly. The reason for having the call to WaitForSingleObject, is in case the main code needs the timer event to complete some action first. But it is not necessary if the remainder of the code does not rely on the actions of the timer event.

Re: DLL with a callback

Bodo240716-Apr-21 4:46

Bodo2407

16-Apr-21 4:46

Hi Richard,

yes, I know that. I did put that in, because I got the exception and wanted to try the example code. This worked two times, so I thought it must be caused by leaving the function. Unfortunately thsi is not the case:
After some debugging runs it seems that (in rare cases) it works a few times, but most likely it crashes immediately. So the observation I made that it is working if I call WaitForSingleObject isn't correct, it can crash randomly with or without.
Unfortunately when it crashs the program pointer isn't on frame any more, so I don't see why it does that.
One observation I made is that the handle of gDoneEvent is allocated in an entirely different address room (0x000003b0) than the other two handles hTimer and hTimerQueue(0x008b8928 and 0x008bsomething) which seems strange to me, since I thought allocated event should be also pretty close to the handles, but obviously it is not.

modified 16-Apr-21 11:04am.

Re: DLL with a callback

Richard MacCutchan16-Apr-21 5:32

Richard MacCutchan

16-Apr-21 5:32

Those numbers do not mean anything, except to the operating system.

mac desing:

prasad 202114-Apr-21 23:09

prasad 2021

14-Apr-21 23:09

Problem 1 — Flawed MAC designs (11 marks) For this problem, you need to carefully trace through the given MAC algorithms, and

Re: mac desing:

Richard MacCutchan14-Apr-21 23:12

Richard MacCutchan

14-Apr-21 23:12

No idea what that is supposed to be. Maybe you lost connection while typing.

Re: mac desing:

Dave Kreskowiak15-Apr-21 4:35

Dave Kreskowiak

15-Apr-21 4:35

You never asked a question, but based on what other people are doing lately, it seems you're just trying to post your homework assignment from Chegg Study, thinking someone is going to write the code for you.

That's not going to happen.

Asking questions is a skill
CodeProject Forum Guidelines
Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

Re: mac desing:

David Crow15-Apr-21 5:39

David Crow

15-Apr-21 5:39

Copy off of the guy sitting next to you. It's your only hope. Roll eyes | :rolleyes:

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

EACCES when not running under VS debugger

ForNow11-Apr-21 10:10

ForNow

11-Apr-21 10:10

Hi
I have a C DLL that processes data for a MFC C++ program. It happens to be my FTP folder where files are received from FTP. when I step thru the code under the VS debugger everything runs fine
I make a breakpoint in the MFC code and when after getting the ProcAddress I go into the function.

So how do I know what the problem is when I don't run under the VS debugger, well I have a SEH (handler that pops up with a messagebox and I attach the debugger and observe the rc from _sopen_s that fails)

I decided to put a MessageBox in when it fails (in the DLL) and upon entry to the DLL as well, in the hope that I can then attach the debugger and get a better idea but the messagebox fails to appear I do re-link the MFC program as well

I went as far a deleting the .lib TO ensure I was picking it up while linking the MFC program and I got a link error so I know its picking the .lib of the DLL

I am running both the (VS Debugger and the MFC program in administrator mode)

Re: EACCES when not running under VS debugger

Richard MacCutchan11-Apr-21 21:27

Richard MacCutchan

11-Apr-21 21:27

Well it could be any one of a million things, but without more information it is pointless trying to guess. Also deleting the .lib file does not guarantee that you are loading the correct .dll at execution time. You should start by rebuilding everything from clean to ensure that no component is out of sync. Secondly, and much more importantly, where does the EACCESS* error occur, and what is the code trying to do at that point?

*EACCESS is returned (most often) when trying to access some file/directory that is protected. And even when running in admin mode some things remain blocked.

Re: EACCES when not running under VS debugger

ForNow12-Apr-21 1:34

ForNow

12-Apr-21 1:34

The EACCESS occurs on _sopen_s the only thing I can think of regarding that is that I have the path + filename and maybe the open function only takes a file name

Regardless I’m gong you’re-build the DLL thanks

Re: EACCES when not running under VS debugger

Richard MacCutchan12-Apr-21 1:52

Richard MacCutchan

12-Apr-21 1:52

What exactly are you trying to open, and what sharing options are you using?

Quote:
EACCES The given path is a directory, or the file is read-only, but an open-for-writing operation was attempted.

Re: EACCES when not running under VS debugger

ForNow12-Apr-21 2:02

ForNow

12-Apr-21 2:02

It’s a mainframe z/os sysadata file which is a binary representation of Z/OS Assembler program listing I have all the big endian conversion routines for going from mainframe to pc it did work as I was able to display the listing in the richedit that called the DLL and processed this file thanks

use of dependent type name must be prefixed

_Flaviu1-Apr-21 7:02

_Flaviu

1-Apr-21 7:02

I have a code:

C++

//add any arg # function to queue
 template <typename Func, typename... Args>
 auto Add(Func&& f, Args&&... args)
 {
     //get return type of the function
     using RetType = std::invoke_result_t<Func, Args...>;

and on last line, at compiling time I got:

error C7510: 'invoke_result_t': use of dependent type name must be prefixed with 'typename'

How can I overcome this error ?

Re: use of dependent type name must be prefixed

Greg Utas1-Apr-21 8:00

Greg Utas

1-Apr-21 8:00

I believe that typename is supposed the be prefixed to tell the compiler that invoke_result_t is defining a type:

using RetType = std::typename invoke_result_t<Func, Args...>;

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Re: use of dependent type name must be prefixed

_Flaviu1-Apr-21 8:25

_Flaviu

1-Apr-21 8:25

I have tried:

C++

using RetType = std::typename invoke_result_t<Func, Args...>;

but I got:

error C2589: 'typename': illegal token on right side of '::'

Re: use of dependent type name must be prefixed

Greg Utas1-Apr-21 10:50

Greg Utas

1-Apr-21 10:50

Try moving it to the front:

C++

using RetType = typename std::invoke_result_t<Func, Args...>;

This[^] may be of help.

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Re: use of dependent type name must be prefixed

_Flaviu1-Apr-21 19:34

_Flaviu

1-Apr-21 19:34

I already did:

C++

using RetType = typename std::invoke_result_t<Func, Args...>;

Result:

error C2760: syntax error: unexpected token '<', expected ';'

Re: use of dependent type name must be prefixed

Greg Utas2-Apr-21 3:02

Greg Utas

2-Apr-21 3:02

See "Helper types" on this page[^]. It looks like invoke_result_t is itself a type alias. Try std::invoke_result without the _t.

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Re: use of dependent type name must be prefixed

Richard MacCutchan2-Apr-21 0:51

Richard MacCutchan

2-Apr-21 0:51

See std::result_of, std::invoke_result - cppreference.com[^], which suggests the word typename goes before std::invoke_result_t. Although the discussion is less clear than it could be.

To print two index in a sentence

Eugene Low31-Mar-21 21:08

Eugene Low

31-Mar-21 21:08

CString isWrong = _T(" is wrong");
CString andMsg = _T(" and ");

bool bCorrect[4];
int numOfFalse = 0;

for(int i=0; i<4; i++){
    bCorrect[i] = true;
    if(arrA[i] != arrB[i]){
        bCorrect[i] = false;
        numOfFalse++;
    }
}

for(int i=0; i<4; i++){
    if((bCorrect[i] == false) && (numOfFalse == 2))
    {
        strRslt.Format("Q%d", i+1);
        m_listRslt.AddString(strRslt + isWrong);
    }
}

I want to print out something like Q1 and Q2 is wrong. Can anyone teach me ?

Re: To print two index in a sentence

Richard MacCutchan31-Mar-21 21:16

Richard MacCutchan

31-Mar-21 21:16

C++

if((bCorrect[i] == false) && (numOfFalse == 2))
{
    strRslt.Format("Q%d%sQ%d%s", i, andMsg, i + 1, isWrong);
    printf("%s\n", strRslt);
}

Re: To print two index in a sentence

Eugene Low31-Mar-21 22:04

Eugene Low

31-Mar-21 22:04

Assume the false value is random assign in the array. The program will check by itself which index has a 'false' then print out the index number.
For example,
index 0 and 3 have 'false', then
print out "Q1 and Q4 is wrong"

Re: To print two index in a sentence

Richard MacCutchan31-Mar-21 23:49

Richard MacCutchan

31-Mar-21 23:49

Try this, which keeps track of the number that are false:

C++

strRslt = "";
int wrong = 0;
for(int i=0; i<4; i++)
{
    if(bCorrect[i] == false)
    {
        if (wrong++ > 0)
            strRslt.AppendFormat("%s", andMsg);
        strRslt.AppendFormat("Q%d", i + 1);
    }
}
if (wrong > 0)
{
    strRslt.AppendFormat("%s", isWrong);
    printf("%s\n", strRslt);
}

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