Problem with loop in C++ - C / C++ / MFC Discussion Boards

Re: RegisterDeviceNotification in dbt.h undeclared identifier??

«_Superman_»24-Jul-13 18:40

«_Superman_»

24-Jul-13 18:40

Simply include <windows.h> as MSDN says.
It works for me.

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

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

Polymorphism in C

Re: RegisterDeviceNotification in dbt.h undeclared identifier??

Richard MacCutchan24-Jul-13 21:24

Richard MacCutchan

24-Jul-13 21:24

The documentation[^] explains which headers to include and versions support this function.

Use the best guess

Re: RegisterDeviceNotification in dbt.h undeclared identifier??

Vaclav_25-Jul-13 7:17

Vaclav_

25-Jul-13 7:17

Here are my "includes" I put into simple MFC test program and it still fails.
What bugs me is that I found others having same problem and the "solution" was to set WINVER to >0x0500.
AS I stated in OP - dbt.h DOES NOT define that function, only makes refrerence to it.
I am still looking for defintion.
Since it fails same when I comment out the #pragma comment I must be missing something else.
I'll keep looking.
Thanks for your help.
Vaclav

#define WINVER 0x0500
#include <C:\Program Files\Microsoft SDKs\Windows\v7.0A\Include\Winuser.h>
#include <stdio.h>
#include <tchar.h>
//#include <strsafe.h>
#include <dbt.h>
#pragma comment (lib,"User32")

Just noticed (in preview) that all #include lines have only #include in it!

Re: RegisterDeviceNotification in dbt.h undeclared identifier??

Jochen Arndt25-Jul-13 7:43

Jochen Arndt

25-Jul-13 7:43

Vaclav_Sal wrote:
I put into simple MFC test program

That is probably the problem when using a stdafx.h file. That files includes various MFC includes which will include the standard Windows header files. So WinUser.h has been already included.

Solution:
Put the WINVER definition on top of your stdafx.h.

Tip:
Format code blocks using the code option above the editor window. Then the <> brackets are treated as they are and not as HTML tag delimiters.

Re: RegisterDeviceNotification in dbt.h undeclared identifier?? SOLVED

Vaclav_26-Jul-13 5:50

Vaclav_

26-Jul-13 5:50

Solution:
Put the WINVER definition on top of your stdafx.h.

Thanks

Re: RegisterDeviceNotification in dbt.h undeclared identifier?? SOLVED

Richard Andrew x6426-Jul-13 12:26

Richard Andrew x64

26-Jul-13 12:26

Thanks for posting the solution.

The difficult we do right away...
...the impossible takes slightly longer.

Re: RegisterDeviceNotification in dbt.h undeclared identifier??

Richard MacCutchan25-Jul-13 9:14

Richard MacCutchan

25-Jul-13 9:14

Vaclav_Sal wrote:
Just noticed (in preview) that all #include lines have only #include in it!

Yes, because as has been suggested before, you should put your code blocks between <pre> tags (use the code button) like:

C++

#define WINVER 0x0500
#include <C:\Program Files\Microsoft SDKs\Windows\v7.0A\Include\Winuser.h> 
#include <stdio.h>

Vaclav_Sal wrote:
AS I stated in OP - dbt.h DOES NOT define that function, only makes refrerence to it.

The link to the documentation that I provided earlier, clearly states that this function is defined in winuser.h and suggests including windows.h to get it. That will also ensure that you get the correct WINVER value for the platform you are building on.

Also, judging by the fact that you have to provide the full path for C:\Program Files\Microsoft SDKs\Windows\v7.0A\Include\Winuser.h, your installation of Visual Studio has not been set up correctly, as this directoy should be one of the default include locations for all projects.

Use the best guess

Problem with loop in C++

Kripa Khanal24-Jul-13 5:40

Kripa Khanal

24-Jul-13 5:40

I have a question regarding the following program. This program uses random variables and asks the user to enter the correct sum for 5 times. Until, we enter an integer the program runs well but as soon as we enter any double value or a character, the program gives incorrect message for the whole loop and comes out of the loop automatically. Why does this happen? Can anyone help me?

C++

#include<iostream> 
#include<ctime> 
using namespace std; 
int main() 
{ 
int num1=0; 
int num2=0; 
int correctanswer=0; 
int useranswer=0; 
srand(static_cast<int>(time(0))); 
for (int x=1; x<6; x++) 
{ 
num1=1+rand()%(100-1+1); 
num2=1+rand()%(10-1+1); 
correctanswer= num1+num2; 
cout<<"What is the sum of "<<num1<<" and "<<num2<<"?"; cin>>useranswer;
 if (useranswer==correctanswer) 
cout<<"Excellent! Correct Answer"; 
     else 
cout<<"Sorry!the correct answer is: "<<correctanswer; cout<<endl<<endl; 
} 
system("pause"); 
return 0; 
}

Re: Problem with loop in C++

pasztorpisti24-Jul-13 7:21

pasztorpisti

24-Jul-13 7:21

The problem is that in case of a wrong answer you leave garbage in your iostream plus the error flags of the iostream may remain set.
A slitly better but still buggy version:

C++

#include<iostream> 
#include<ctime>
#include <limits>
using namespace std; 
int funccccc() 
{ 
    int num1=0; 
    int num2=0; 
    int correctanswer=0; 
    int useranswer=0; 
    srand(static_cast<int>(time(0))); 
    for (int x=1; x<6; x++) 
    { 
        num1=1+rand()%(100-1+1); 
        num2=1+rand()%(10-1+1); 
        correctanswer= num1+num2; 
        // The inner loop is needed if we want to ask the same question after an invalid input value.
        for (;;)
        {
            cout<<"What is the sum of "<<num1<<" and "<<num2<<"?"; cin>>useranswer;
            if (!cin.fail())
                break;
            cin.clear();
            cin.ignore(std::numeric_limits<streamsize>::max(),'\n');
            cout << "Invalid value!" << endl;
        }

        if (useranswer==correctanswer) 
            cout<<"Excellent! Correct Answer" <<endl;
        else 
            cout<<"Sorry!the correct answer is: "<<correctanswer; cout<<endl<<endl; 
    }

    system("pause"); 
    return 0; 
}

The bug in this version is the following:
Lets say you answer 5.6 for the first question. In this case your first cin>>useranswer statement will read out "5" into the useranswer by ignoring everything from the input stream from the '.' character. It evaluates the first question with your answer '5' and then it asks the next question. Since we still have characters in the input stream the cin>>useranswer statement of the next question tries to read it as an integer. Unfortunately it fails and our error handler clears the error flags and discards everything from the input stream till the next newline character. From the next question everything is OK. If you simply enter a garbage string that doesn't start with a digit then it works perfectly. The bug of this solution occurs if you enter a garbage string whose first character is a digit like "5sfldfhwei".

You could correct this by always reading in everything till the next newline, stripping the spaces from the left and right side of the string and trying to interpret it as it is without ignoring any characters in the string. I'm not a big iostream fan/user and I don't know how to interpret a string as an integer with iostream without ignoring any characters from the right side of the string.

Re: Problem with loop in C++

Kripa Khanal25-Jul-13 12:06

Kripa Khanal

25-Jul-13 12:06

Thank you so much pasztorpisti. Your reply was very helpful. I appreciate your help. Thanks once again Smile | :)

Re: Problem with loop in C++

pasztorpisti25-Jul-13 22:59

pasztorpisti

25-Jul-13 22:59

You are welcome!

Re: Problem with loop in C++

Member 1014853124-Jul-13 16:13

Member 10148531

24-Jul-13 16:13

I test your process in VC6 and it running OK.

Serial Port Functor

Jonathan Davies24-Jul-13 1:51

Jonathan Davies

24-Jul-13 1:51

Hi,
Reading the below answers regarding serial ports made me wonder how safe these (below) calls would be considered. There's no need to pass anything to the constructor as in the reasons I read for using functors, and I only use them in this form because I wrote then when using STL and they're nice one liners really.

C++

hPort = CPortOpener()(hWnd, wszPort);

and

C++

CEditPortSettings()(hWnd, hPort, wszPort);

which use for instance:

C++

class CEditPortSettings
{
public:
    CEditPortSettings(void);
    
    long operator()(HWND hWnd, HANDLE hPort, std::wstring szPort)
    {
        ...
        return anyerror;    
    }

Re: Serial Port Functor

pasztorpisti24-Jul-13 3:29

pasztorpisti

24-Jul-13 3:29

It is exactly as safe as a normal function call with the same signature in this case. Functors are better than normal function/method calls only if you want to pass a function to a template method because using function pointers is not comfortable in an object oriented language that doesn't support delegates (delegate == function pointer that has the ability to point to the method of an object).

Regarding your constructor declaration: CEditPortSettings(void);
You have to say (void) in the parameter list of a function only in C. In C if you don't use void in case of an empty parameter list then the function is automatically vararg. In C++ the same isn't true so using void is unnecessary. I see (void) parameter list quite rarely in C++ code.

Re: Serial Port Functor

C^hris L^osinger24-Jul-13 10:26

C^hris L^osinger

24-Jul-13 10:26

what does that offer over a normal function call? besides increased unreadability...

image processing toolkits | batch image processing

Re: Serial Port Functor

Jonathan Davies24-Jul-13 10:36

Jonathan Davies

24-Jul-13 10:36

Nothing

GetModuleFileName and case sensitivity

vikramlinux23-Jul-13 23:19

vikramlinux

23-Jul-13 23:19

Hi Guys,
I am using GetModuleFileName API in my program. It returns me the name of my executable. However, I see that under different environments, it give me output like

-- Win XP
output: test.exe
-- Win 7
output: TEST.EXE

not sure why the API gives me different outputs. Please help.

Re: GetModuleFileName and case sensitivity

«_Superman_»23-Jul-13 23:27

«_Superman_»

23-Jul-13 23:27

Here is an excerpt from the documentation for GetModuleFileName -
The string returned will use the same format that was specified when the module was loaded. Therefore, the path can be a long or short file name, and can use the prefix "\\?\".

So the output will depend on how your EXE was loaded.

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

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

Polymorphism in C

Re: GetModuleFileName and case sensitivity

vikramlinux23-Jul-13 23:32

vikramlinux

23-Jul-13 23:32

"So the output will depend on how your EXE was loaded."

Can you please help in elaborating it more?

Re: GetModuleFileName and case sensitivity

vikramlinux23-Jul-13 23:36

vikramlinux

23-Jul-13 23:36

To add more context, we are using CreateProcess(...) API to launch the exe file. However, even though the code is same but GetModuleFileName returns me different output.

Re: GetModuleFileName and case sensitivity

Richard MacCutchan24-Jul-13 0:25

Richard MacCutchan

24-Jul-13 0:25

It would be better if you explained what problem this is causing you. The character case of an executable filename is not significant in Windows. If you want to read the full documentation it is at http://msdn.microsoft.com/en-us/library/windows/desktop/ms683197(v=vs.85).aspx[^].

Use the best guess

Re: GetModuleFileName and case sensitivity

SajeeshCheviry24-Jul-13 0:24

SajeeshCheviry

24-Jul-13 0:24

Vikrams..pls read it http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx. I think this may be the reason. Smile | :)

Re: GetModuleFileName and case sensitivity

vikramlinux24-Jul-13 1:23

vikramlinux

24-Jul-13 1:23

I went though it, but able to get the reason.