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13hrs 46mins ago

Version of a console application

_Flaviu15-Apr-21 22:10

_Flaviu

15-Apr-21 22:10

How can I know the version of an console application executable ? (obviously, this exe is not made it by me)

Richard MacCutchan15-Apr-21 22:50

15-Apr-21 22:50

Unless the executable contains version information you can't. It is possible to add version information in a resource definition file when building a console app, but few people do so. Right click the .exe and check the properties.

_Flaviu15-Apr-21 22:55

_Flaviu

15-Apr-21 22:55

Yes, I have checked properties in Windows, Explorer, but show me nothing. I thought there is another way to find it.

Richard MacCutchan15-Apr-21 23:03

15-Apr-21 23:03

In that case it does not contain 'standard' version information. There may be other information held in the program but only the creators will know where it is.

Maximilien16-Apr-21 6:13

Maximilien

16-Apr-21 6:13

does it have by chance a "-v" or "-version" or "/version" command line parameter ?

I'd rather be phishing!

CPallini16-Apr-21 8:01

CPallini

16-Apr-21 8:01

How do you know that such executable actually has a version?

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Mircea Neacsu12hrs 24mins ago

Mircea Neacsu

12hrs 24mins ago

Have you looked at the date field in the PE header?
See PE Format - Win32 apps | Microsoft Docs[^]

It’s not exactly a version information but it might give you an ordering of the different versions. That’s assuming the linker used to create the app bothered to fill it. Most, but not all, do.

Mircea

DLL with a callback

Bodo240715-Apr-21 6:05

15-Apr-21 6:05

Hi!
I try to implement a callback function within a dll, which triggers an assigned function in the main application. I want to trigger this "event" in the main app from within the dll.

Here is my code from the dll:

C++

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//a normal function I call from the main application:
extern "C" __declspec(dllexport) void funcA(const unsigned long long a, const unsigned long long b);
//following function should be the callback, triggering an assigned function in the main application
extern "C"
{
    typedef void(__stdcall* callback_t)(unsigned int halfbeast);

    __declspec(dllexport) void public_func_taking_callback(callback_t evHnd)
    {
        evHnd(333);//value just for testing
    }
}


void funcA(
    const unsigned long long a,
    const unsigned long long b)
{
    //some code here... do things with a and b
   if(a>10)                       //trigger the event in the main application
       callback_t(public_func_taking_callback);   
}

Here is the code I use in the main application to load the library and attach to the functions:

C++

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typedef void (__stdcall *eventCallback)(unsigned int miau);
typedef void (__stdcall *setCallback)(eventCallback evHnd);
void __stdcall CallB(unsigned int);

//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
signed int retval;
unsigned int i;
char txt[7];
unsigned long long a,index;
UnicodeString USt;
HINSTANCE dllHandle=NULL;

//Obtain a handle to the DLL
dllHandle = LoadLibrary(L"test.dll");
if (!dllHandle){
    ShowMessage("Could not load test.dll");
    Form1->Close();
    }
else{    //Lib was loaded, try to get data
    void (__stdcall* funcA)(const unsigned long long a, const unsigned long long b);  
    funcA=(void(__stdcall*)(const unsigned long long a, const unsigned long long b))GetProcAddress(dllHandle,"funcA");

    // DLL function pointer
    setCallback values=(setCallback)GetProcAddress(dllHandle, "public_func_taking_callback");
    if(values != NULL){
        values(&CallB);
        }

    if(!funcA){
        Memo1->Text="No handle to function found.";
        }
    else{
        funcA(1,1);
        funcA(100,100);
        }
    FreeLibrary(dllHandle);
    }

}
//---------------------------------------------------------------------------
void __stdcall CallB(unsigned int halfbeast){
ShowMessage("triggered");
}
//---------------------------------------------------------------------------

What happens is unfortunately not what I wanted:
1) In the very moment the line "values(&CallB);" is executed, CallB is called. This is not what I wanted, I justed wanted to give the callback pointer of the dll to my function CallB.
2) CallB is not called when the line "funcA(100,100);" is executed. Most likely there is something wrong with the function call within the dll, but I cannot see it...

Richard MacCutchan15-Apr-21 6:27

15-Apr-21 6:27

1. That is correct. At that point, values is set to public_func_taking_callback, which takes the address of a function and immediately calls it.
2. funcA calls callback_t, but callback_t has never been set to any value.

To be honest, I find it difficult to understand your code, so I may have still missed something. However, you should be able to see the exact sequence of events by running the code in the debugger.

Bodo240715-Apr-21 6:41

15-Apr-21 6:41

Hi Richard,
thanks for the answers. Yes I can debug it, but it doesn't help me much, since I don't understand why it behaves that way.
1.) OK, got it. Unfortunately then I do not know, how I pass the address of the function of CallB to the dll. I want the dll to call CallB() in the moment callback_t is called.

Most likely I confuse here something, but I find it very hard to understand the syntax. It seems even harder since it is wrong Big Grin | :-D

I wasn't able to find any C++ examples for that.

2.) I thought I set it to public_func_taking_callback, but obviously this is not the case.

Maybe I should explain again, what I try to do:
In my main application I want to declare a function. This function should be registered in the dll as a callback function. When during run time in the dll some criteria match ( if(a>10) ) the dll should call the function in the main application and execute it.

Richard MacCutchan15-Apr-21 6:55

15-Apr-21 6:55

Bodo2407 wrote:
I don't understand why it behaves that way.

It behaves that way because that is the way you have written the code.

1. So you need to change the code in public_func_taking_callback as follows:

C++

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__declspec(dllexport) void public_func_taking_callback(callback_t evHnd)
{
 //   evHnd(333);//value just for testing // this was causing your problem
    callback_t = evHnd; // save the callback address for funcA.
}

And you need to change funcA to:

C++

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if(a>10)                       //trigger the event in the main application
    callback_t(a);   // the callback is set to invoke void __stdcall CallB(unsigned int halfbeast)

Again, make these changes and then step through the code in the debugger to check that it is correct.

Bodo240715-Apr-21 7:33

15-Apr-21 7:33

Hi Richard,

thanks a lot, but unfortunately it cannot compile:

C++

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__declspec(dllexport) void public_func_taking_callback(callback_t evHnd)
{
 //   evHnd(333);//value just for testing // this was causing your problem
    callback_t = evHnd; // save the callback address for funcA. //this line doesn't compile
}

Failure given:
-Error C2513 'void (__stdcall *)(unsigned int)': no variable declared before '='

So the typedef earlier doesn't work or... ?

CPallini15-Apr-21 20:51

CPallini

15-Apr-21 20:51

callback_t is a type, not a function.
In your DLL, you do need a variable of such a type, in order to store the user function address.
Something similar to (not tested)

C++

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typedef void (__stdcall* callback_t) (unsigned int halfbeast);
static callback_t s_user_function = nullptr; // variable used to store the user function address

extern "C" __declspec(dllexport) void funcA(const unsigned long long a, const unsigned long long b);
//following function should be the callback, triggering an assigned function in the main application
extern "C"
{
    __declspec(dllexport) void public_func_taking_callback(callback_t evHnd)
    {
        s_user_function = evHnd; // store the passed user function address
    }
}


void funcA(
    const unsigned long long a,
    const unsigned long long b)
{
    //some code here... do things with a and b
   if(a>10 && s_user_function != nullptr)                       //trigger the event in the main application
       s_user_function(333); // call the user function
}

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Richard MacCutchan15-Apr-21 22:44

15-Apr-21 22:44

Thanks Carlo, I missed that.

Bodo240715-Apr-21 23:04

15-Apr-21 23:04

Thanks a lot guys! It works now!
I really appreciate your help.
Now it also makes much more sense to me. Big Grin | :-D

CPallini15-Apr-21 23:24

CPallini

15-Apr-21 23:24

As you pointed out, the OP code looked a bit confused.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Richard MacCutchan16-Apr-21 0:17

16-Apr-21 0:17

CPallini wrote:
a bit confused

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

Bodo240716-Apr-21 3:47

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++

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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++

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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...

Richard MacCutchan16-Apr-21 4:33