Re: OOP - Error | Unhandled exception at 0x0FD2CCC8 (msvcp110d.dll)

Richard MacCutchan10-Jun-15 21:32

10-Jun-15 21:32

1. This does not look like managed code.
2. Please use <pre> tags round your code to make it more readable.
3. What is the structure of the teacher type?
4. How is the data file created?
5. What does the Display method do?

Enabling ListControl pane in MFC (C++)

Yateesh KR12-May-15 22:14

Yateesh KR

12-May-15 22:14

i have created a simple window using MFC application wizard but i can see only navigation pane(which is in left side of window). Can anyone tell how to view those contents on List view pane.

Re: Enabling ListControl pane in MFC (C++)

Richard MacCutchan13-May-15 2:55

Richard MacCutchan

13-May-15 2:55

That sounds like a bit more that a 'simple' window. What type of control is in each pane?

Inheritance tricky question

Amrit Agr12-May-15 9:30

Amrit Agr

12-May-15 9:30

Hi Friends,

I came through a interesting question in inheritance. Here is the chunk of code and out put is given below.

// Inheritance tricky.cpp : Defines the entry point for the console application.
//

class Foo
{
private:
int i;
public:
Foo()
{
i = 0;
}
void geti()
{
cout << i << endl;
}
};

class Bar : public Foo
{
private:
int j;
public:
Bar()
{
j = 1;
}
void getj()
{
cout << j << endl;
}
};

void display(Foo* obj, int ctr)
{
for (int i = 0; i < ctr; i++)
{
((Foo*)obj + i)->geti();
}
}

int _tmain(int argc, _TCHAR* argv[])
{
Foo myFoo[3];
display(myFoo, 3);

Bar myBar[3];
display(myBar, 3);
return 0;

}

and Output is

0
0
0
0
1
0

The first 3 line is 0 that's fine. But how the 2nd last is 1 ???

Is there is any way that I can get all 0 in output if I am still executing this code

Bar myBar[3];
display(myBar, 3);

PLease help me out.

Thanks in Advance.
Regards,
Amrit

-- modified 12-May-15 15:52pm.

Re: Inheritance tricky question

Sascha Lefèvre12-May-15 11:38

Sascha Lefèvre

12-May-15 11:38

myBar[1].i is still 0. The problem here is that you try to apply pointer-arithmetic to a base-class pointer. When you add 1 to Foo* obj in the loop in display(..), the pointer is increased by the size of Foo, because it's declared as a pointer to Foo. But it's actually (initially) pointing to instances of Bar, whose size is larger than that of Foo - so after adding 1 to the pointer, it points to some address still within the first instance of Bar, not to the second Bar. The output of 1 is whatever happens to be at the address where i should be if the pointer was valid.

The closest thing you can do to make it work is to use pointers to pointers:

C++

void display2(Foo** obj, int ctr)
{
    for (int i = 0; i < ctr; i++)
    {
        (*(obj + i))->geti();
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    Foo myFoo[3];
    display(myFoo, 3);

    Bar myBar[3];
    Foo *myBaz[3] = { &myBar[0], &myBar[1], &myBar[2] };
    display2(myBaz, 3);

    return 0;
}

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Re: Inheritance tricky question

Amrit Agr13-May-15 7:47

Amrit Agr

13-May-15 7:47

Hi Sascha,

I am not able to understand why we need to take address of Bar objects in line
Foo *myBaz[3] = { &myBar[0], &myBar[1], &myBar[2] };

and why we need to pass to pass the address of myBaz to a Foo** ( Double Pointer )?

How surprisingly its working fine now?

One more thing I still didn't get it hpw it prints 1 for 2nd iteration of Bar object.

If I am not wrong, even if we are passing Bar address to Foo pointer, it wil call the geti function of Foo only ? so It should print variable i value that is 0 ?

Please clear my doubt.

Thanks

Re: Inheritance tricky question

Sascha Lefèvre13-May-15 9:12

Sascha Lefèvre

13-May-15 9:12

Hi Amrit,

I'll try to explain it with some diagrams.

First, the simple case - you probably know this, but I'll show it for completeness. The class Foo has a single member of type int (int32), so it has a size of 4 bytes.

C++

# 3 instances of Foo in memory with a Foo* pointer pointing to it:

Foo myFoo[3];      // in _tmain(..)

Foo* ptr = myFoo;  // calling display(..)   (I renamed *obj to *ptr here)

#                  ptr       ptr+1     ptr+2      // the loop in display(..)
#                  (100)     (100+4)   (100+8)
#                  |         |         |
#                  v         v         v
# Memory address:  100..103  104..107  108..111   // (artificially chosen address)
# Instance:        --Foo1--  --Foo2--  --Foo3--
# Members:         ---i----  ---i----  ---i----

Now with the class Bar (8 bytes) and your original approach:

C++

# 3 instances of Bar in memory with a Foo* pointer pointing to it:

Bar myBar[3];      // in _tmain(..)

Foo* ptr = myBar;  // calling display(..)

#                  ptr    ptr+1    ptr+2     // the loop in display(..)
#                  (100)  (100+4)  (100+8)   // here's why it doesn't work: 
#                  |      |        |         // ptr is Foo* so ptr+1 still means adding the size of Foo (4) !
#                  v      v        v
# Memory address:  100........107  108........115  116........123
# Instance:        -----Bar1-----  -----Bar2-----  -----Bar3-----
# Members:         ---i---___j___  ---i---___j___  ---i---___j___

# Value:              0      1        0   // and there's your strange output! ;-)

And now with pointers to pointers. Let's say we're on a 32bit-system here, then a pointer has the size of 4 bytes (32 bit). So, when doing pointer arithmetic with pointers to pointers, adding 1 means always increasing its pointed-to-address by 4 bytes. It doesn't have anything to do with the size of the class that's being pointed to by the pointer that's being pointed to Big Grin | :-D

C++

# 3 instances of Bar in memory with a Foo** pointer pointing to Bar* pointers:

Bar myBar[3];       // in _tmain(..)
Foo *myBaz[3] = { &myBar[0], &myBar[1], &myBar[2] };
# Value:           100        108        116

Foo** pptr = myBaz; // calling display2(..)          (for clarity, I named it pptr here)

#                  pptr       pptr+1     pptr+2
#                  (200)      (200+4)    (200+8)     // see explanation above (32 bit..)
#                  |          |          |
#                  v          v          v
# Memory address:  200        204        208         // (artificially chosen address)
# Pointer:         &myBar[0]  &myBar[1]  &myBar[2]
# Value:           100        108        116
#                  |            \           \__
#                  |             \             \__
#                  | *pptr        \ *(pptr+1)     \ *(pptr+2)  // resolving from pptr to ptr
#                  v               v               v
# Memory address:  100........107  108........115  116........123
# Instance:        -----Bar1-----  -----Bar2-----  -----Bar3-----
# Members:         ---i---___j___  ---i---___j___  ---i---___j___

Does this answer your questions?

/Sascha

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

english language implementation

Member 936602117-Apr-15 3:58

Member 9366021

17-Apr-15 3:58

Dear programmers,
I want to implement English language feature in the following applicationhttp://www.codeproject.com/Articles/714651/Desktop-Sharing-using-RDP-APIs-and-Socket
.
I followed this http://stackoverflow.com/questions/12929934/same-resource-identifier-in-different-language-sections-in-an-rc-file-why-is-it post and https://msdn.microsoft.com/en-us/goglobal/bb688160.aspx
Now my peer.rc file code is

<pre lang="c++"><pre lang="c++"><pre lang="c++">

//
// Peer.RC2 - Microsoft Visual C++ ?????????
//

ifdef string ID IDS_ENUMSTRTEST

error Microsoft Visual C++

endif //APSTUDIO_INVOKED

/////////////////////////////////////////////////////////////////////////////
// ????????????...
/////////////////////////////////////////////////////////////////////////////
That works fine .
But I cannot change the language to English as I want.
Please suggest the appropriate changes in the code that works for me.
Please note that I am using vs2013 ultimate edition for that purpose.
Also when I click on the client software I get the following error that is in Chinese and unable to understand.

image here.
https://www.transferbigfiles.com/3464a589-c488-479a-a2c5-94455bc7d651/ug4vGWwsrMVO1Nnq-WXY3w2

Re: english language implementation

Member 936602117-Apr-15 4:00

Member 9366021

17-Apr-15 4:00

All the resource files and dlls are changed to English but cannot find the reason of displaying the Chinese language.

Peer.rc code is now that compiles fine.

#ifdef string ID IDS_ENUMSTRTEST#error  Microsoft Visual C++ #endif //APSTUDIO_INVOKED

Thanks

multiple

memoarfaa16-Apr-15 1:28

memoarfaa

16-Apr-15 1:28

How do I can split file over 4gb in fat32 in to multiple file with same name and same directory

cygwin1.dll can do this in iso9660 file system

Re: multiple

Richard MacCutchan16-Apr-15 2:20

Richard MacCutchan

16-Apr-15 2:20

You cannot, unless you create the directories across different root paths. In any directory each file name must be unique.

How to swap address of pointers of 2 variables without using a temporary variable?

Amrit Agr13-Apr-15 20:36

Amrit Agr

13-Apr-15 20:36

Hi guys,

I have asked this question in an interview

How to swap address of pointers of 2 variables without using a temporary variable?

As I know the arithmetic operation is not allowed between 2 pointers. So what is the trick ?

Pls help me out. Thanks in advance.

Regards,
Amrit

Re: How to swap address of pointers of 2 variables without using a temporary variable?

jschell14-Apr-15 13:17

jschell

14-Apr-15 13:17

Amrit Agr wrote:
Pls help me out

Perhaps it is helpful to know that the interviewer probably didn't know what they were doing in terms of interviewing.

Hopefully you were asked some other questions which were in fact more relevant.

Amrit Agr wrote:
So what is the trick ?

Being interesting to see if there is in fact a correct answer. Just googling suggests that the standard C/C++ answer which, as you noted, is not in fact the same as Managed C++ makes it very unlikely that you can in fact do it without an intermediary. And if possible it would require more consideration than just whether it was a pointer or not.

Re: How to swap address of pointers of 2 variables without using a temporary variable?

zhijzan7-Jun-15 20:40

zhijzan

7-Jun-15 20:40

you can use swap() method in c/c++,
is this you want?

Re: How to swap address of pointers of 2 variables without using a temporary variable?

Shao Voon Wong28-Jun-15 22:13

Shao Voon Wong

28-Jun-15 22:13

XOR swap algorithm[^]

X := X XOR Y
Y := X XOR Y
X := X XOR Y

But you cannot do this with pointers as compiler does not allow XOR operation on pointers, you have to cast pointer to integer(32bit ptr to 32bit integer and 64bit ptr to 64bit integer) beforehand. This is a favourite interview question among some interviewers (who apparently read the same interview book).

how to migrate CORBA to Web Service in C++

VC_RYK13-Apr-15 20:20

VC_RYK

13-Apr-15 20:20

Hi Experts,

I have a server written in C++, Client is in JAVA and middle-ware is CORBA, now we are planing to replace CORBA by web Service(SOAP or REST). we don't want to make any changes in our business logic just want to replace CORBA by web service. Can anyone give some idea how do i approach. since I googled a lot, how to write a REST or SOAP service in C++ but didn't get any lead.

Please do let me know if you seek any further info

Thanks in advance
RYK

consumer.C: In function âint main(int, char**)â: consumer.C:69: error: invalid conversion from âvoid (*)(buffer_t*, char)â to âvoid* (*)(void*)â consumer.C:69: error: initializing argument 3 of âint pthread_create(pthread_t*, const pthread_attr_t*,

Member 1160464113-Apr-15 15:29

Member 11604641

13-Apr-15 15:29

I've been getting this error when I compile in my Consumer/Producer Multi-threaded program. Can someone please help me Smile | :)

? Here is my code

C++

#include <iostream>
#include <stdio.h>
#include <pthread.h>
#include <assert.h>
#include<complex>

# define BSIZE 10
# define NUM_THREADS 5
using namespace std;


typedef struct {
  char buf[BSIZE];
  int occupied;
  int nextin;
  int nextout;
  pthread_mutex_t mutex;
  pthread_cond_t more;
  pthread_cond_t less;
} buffer_t;

buffer_t buffer;

void producer(buffer_t *b, char item)
{
  pthread_mutex_lock(&b->mutex);

  while (b->occupied >= BSIZE)
    pthread_cond_wait(&b->less, &b->mutex);

  assert(b->occupied < BSIZE);

  b->buf[b->nextin++] = item;

  b->nextin %= BSIZE;
  b->occupied++;
  pthread_cond_signal(&b->more);

  pthread_mutex_unlock(&b->mutex);
}

char consumer(buffer_t *b)
{
  char item;
  pthread_mutex_lock(&b->mutex);
  while(b->occupied <= 0)
    pthread_cond_wait(&b->more, &b->mutex);

  assert(b->occupied > 0);

  item = b->buf[b->nextout++];
  b->nextout %= BSIZE;
  b->occupied--;

  pthread_cond_signal(&b->less);
  pthread_mutex_unlock(&b->mutex);

  return(item);
}

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


  pthread_t ptid;
  pthread_attr_t attr;

  pthread_attr_init(&attr); /* initialize attr with default attributes */
 pthread_create(&ptid, &attr, producer  , NULL);



}

modified 13-Apr-15 22:13pm.

Re: consumer.C: In function âint main(int, char**)â: consumer.C:69: error: invalid conversion from âvoid (*)(buffer_t*, char)â to âvoid* (*)(void*)â consumer.C:69: error: initializing argument 3 of âint pthread_create(pthread_t*, const pthread_attr

Richard MacCutchan13-Apr-15 21:33

Richard MacCutchan

13-Apr-15 21:33

Your declaration of the producer function, does not match the definition required by pthread_create, see http://man7.org/linux/man-pages/man3/pthread_create.3.html[^].

int **p = (int**)new int(5); Confusing !!!

Amrit Agr5-Apr-15 8:32

Amrit Agr

5-Apr-15 8:32

Hey Guys,

I am trying to execute the following chunk of code.

int **p = (int**)new int(5);
cout << *p;

I am getting output 00000005

As per my understanding , we don't need to typecast return value from new, as it automatically does.
Like in the following statement

int *ap = new int(20);

We don't need to do that, So why I need to do in case of double pointer??

Second thing is, in cout statement, I need to put pointer deference operator once not twice. Even after that i am getting strange output like 00000005

Please someone help me.

Thanks
Amrit

Re: int **p = (int**)new int(5); Confusing !!!

Richard Andrew x645-Apr-15 10:14

Richard Andrew x64

5-Apr-15 10:14

Amrit Agr wrote:
So why I need to do in case of double pointer??

Who said you do? This ought to work just fine:

int **p = new (int*);
*p = new int;

**p = 5;

cout << **p;

delete *p;
delete p;

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

Re: int **p = (int**)new int(5); Confusing !!!

Zabir Al Nazi Nabil5-Apr-15 11:34

Zabir Al Nazi Nabil

5-Apr-15 11:34

here, p is a pointer to int*.that means p can point to an int pointer and that pointer will point an int type of data.
when you do this , (int**) new int (5) ; you are actually forcing (casting) p to point to an int pointer (memory address) with value 5 ..(It actually should not be done because you don't know anything about memory address 0x5 )... however and as you made p to store something(a memory address with value 5) you also allocated memory for that purpose ......

and the typecasting was necessary as first case is very different than the second case....
in the second case --- ap is an int pointer and with new command you allocated 4 bytes of memory for ap .. and ap is now pointing to that memory location and as you passed 20 in the constructor so now that memory address is storing 20....
But, p is not an int pointer ..it's a pointer to int pointer ...so it should be passed a valid memory address in the constructor call .. not an int(what you did -- by passing 5)..that's why you had to cast...
and the answer to your last question is ... p is just a pointer (it maybe a pointer to another pointer but it still is a pointer)..and when we want to know what value a pointer is pointing to we put * (deference op.) before that pointer (only once)!
Hope,you got that Big Grin | :-D

solitaire game

Member 115602925-Apr-15 4:19

Member 11560292

5-Apr-15 4:19

I am a beginner in programming and have to write a solitaire program(C++) just like what we play in windows. I have no idea where or how I should start my program. I never write a game in any computer language and I have already stuck at the beginning for 2 weeks. Can you help??
btw I just need to finish the game logic and give it to my teammate to work on graphic(GUI).

now I just write a few line about checking whether the move in those 7 piles are valid or not and create 52 cards in a class by using array but cannot generate each card uniquely.

Re: solitaire game

Richard MacCutchan5-Apr-15 5:39

Richard MacCutchan

5-Apr-15 5:39

That is not a simple question to answer in a forum like this. You should start with a couple of classes:
Card - contains properties such as value and suit.
Player - contains a List of cards.
Some general methods:
A randomiser that deals the cards around.
Play that selects a card and figures out where it can be placed

etc.
Quite a lot to think about before you start coding, or worrying about the UI.

Fast object tracking code

Member 1051522512-Mar-15 22:35

Member 10515225

12-Mar-15 22:35

Dear all.
I am using kinect SDK2.0. Kinect sensor 2.0; visual studio 2012 & openCV 2.4.10 installed in my system.\

I am new to this kinect platform.I am looking for c++ code test some simple code. I have tested code with SDK2.0 . those are working fine. But i didnt find the code where they add images features resources . code to track object

I would like to detect object like in youtube video
<a href="https://www.youtube.com/watch?v=bSeFrPrqZ2A">object tracking using opencv</a>[<a href="https://www.youtube.com/watch?v=bSeFrPrqZ2A" target="_blank" title="New Window">^</a>]

how to use hook for mouse simulation

Omarkkk10-Mar-15 2:02

Omarkkk

10-Mar-15 2:02

Hi all,

i need to simulate mouse events using hooks.
I read the the msdn articles about hook and how they are used but I felt that they are complex!!

could any one help me or guide me on how to do the following:

- just send one mouse event to a window that is not mine. The window is a running application such as notepad, so I just need to send the right click for example to it!

thanks for any help Smile | :)

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

Managed C++/CLI

ifdef string ID IDS_ENUMSTRTEST

error Microsoft Visual C++

endif //APSTUDIO_INVOKED