C / C++ / MFC

6-Jan-08 3:06

babamara wrote:
SetWindowPos(&wndTop+21

?!?

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

static pointer

jupiter10005-Jan-08 11:59

jupiter1000

5-Jan-08 11:59

Hi,

I have the following class declared:

// header file
class classA
{
protected:
static classA *a;
static void setClassA(classA *pa);
}

// *.cpp file
#include "classA.h"

void classA::setClassA(classA *pa)
{
classA::a = pa;
return;
}

This code compiles just fine but it does not link.
The error I get is:
unresolved external symbol "protected static class classA *classA::a"

Re: static pointer

CPallini5-Jan-08 12:22

5-Jan-08 12:22

You need to define the static member pointer. Write the following statement in the source (*.cpp) file

classA * classA::a = NULL;

BTW you missed a semicolon at the end of the class declaration.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Re: static pointer

jupiter10005-Jan-08 12:46

jupiter1000

5-Jan-08 12:46

Thank you for the quick response. It works now.
I have been doing some research in the meantime.
I am not sure if I understand why I have to do this extra reference.
Is it because static limits the visibility of the variable to the include <.h> file?

Re: static pointer

CPallini5-Jan-08 13:10

Problem with mirrored bitmap

5-Jan-08 13:10

jupiter1000 wrote:
I am not sure if I understand why I have to do this extra reference.
Is it because static limits the visibility of the variable to the include <.h> file?

According to MSDN [^]

Static data members are not part of objects of a given class type; they are separate objects. As a result, the declaration of a static data member is not considered a definition. The data member is declared in class scope, but definition is performed at file scope. These static members have external linkage

Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

AnTri5-Jan-08 9:04

AnTri

5-Jan-08 9:04

Hey, I use my printer dc to paint some text and graphic to my printer. I use MM_LOMETRIC as Mapmode because of the easy way of positioning. Now I have a big problem to print bitmaps. All bitmaps are mirrowed (around X-axis).

I use the following code to paint the bitmap:

<br />
<br />
<br />
....<br />
CBitmap *pBitmap = new CBitmap();<br />
HBITMAP hBitmap;<br />
hBitmap = (HBITMAP)::LoadImage(AfxGetInstanceHandle(),szPathToBitmap,IMAGE_BITMAP,0,0,LR_LOADFROMFILE|LR_CREATEDIBSECTION);<br />
pBitmap->Attach(hBitmap);<br />
...<br />
<br />
<br />
<br />
CRect reRect;<br />
<br />
reRect.left = 10;<br />
reRect.right = 300;<br />
reRect.top = -100;<br />
reRect.bottom = -1000;<br />
<br />
CDC dcMem;<br />
BITMAP bm;<br />
<br />
pBitmap->GetBitmap(&bm);<br />
dcMem.CreateCompatibleDC(pDC);<br />
dcMem.SelectObject(pBitmap);<br />
pDC->BitBlt(reRect.left, reRect.top, bm.bmWidth, bm.bmHeight, &dcMem,0,0, SRCCOPY);<br />
<br />
<br />

What's wrong, and how could I fix it?

Re: Problem with mirrored bitmap

Mark Salsbery5-Jan-08 9:50

Mark Salsbery

5-Jan-08 9:50

Maybe try

//pDC->BitBlt(reRect.left, reRect.top, bm.bmWidth, bm.bmHeight, &dcMem,0,0, SRCCOPY);
// Mirror the blt around the X axis...
pDC->StretchBlt(reRect.left, reRect.top, bm.bmWidth, -bm.bmHeight, &dcMem, 0, 0, bm.bmWidth, bm.bmHeight, SRCCOPY);

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Problem with mirrored bitmap

AnTri5-Jan-08 10:24

AnTri

5-Jan-08 10:24

Thanks, this works fine for me (only the position is shifted), but why is the bitmap mirrored?

Re: Problem with mirrored bitmap

Mark Salsbery5-Jan-08 10:30

Mark Salsbery

5-Jan-08 10:30

AnTri wrote:
but why is the bitmap mirrored?

The Y-axis is flipped by MM_LOMETRIC and BitBlt() renders
scanlines in the positive direction from the starting point.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

memory leak in the code?

George_George5-Jan-08 4:02

5-Jan-08 4:02

Hello everyone,

Should I delete memory pointed by pointer a if there is bad_alloc when allocating memory in memory pointed by pointer b? I am not sure whether there will be memory leak if I do not delete a.

try {
    a = new int [N];
    b = new int [M];
} catch (bad_alloc)
{
    // if a success, but b fail, should we try to delete[] a here to avoid memory leak?

}

thanks in advance,
George

CPallini5-Jan-08 4:09

5-Jan-08 4:09

You have always to do your cleanup stuff!
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

George_George5-Jan-08 4:16

5-Jan-08 4:16

Thanks CPallini!

I think you mean we have to delete A, right?

regards,
George

CPallini5-Jan-08 4:20

5-Jan-08 4:20

Yes.

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

George_George6-Jan-08 2:45

6-Jan-08 2:45

Thanks for your confirmation, CPallini!

regards,
George

Eytukan5-Jan-08 18:39

Eytukan

5-Jan-08 18:39

But I suggest he should do something like this :

<br />
if(pMyStuff!=NULL)<br />
{<br />
  delete pMyStuff;<br />
}<br />

OK,. what country just started work for the day ? The ASP.NET forum is flooded with retarded questions. -Christian Graus

Best wishes to Rexx[^]

CPallini5-Jan-08 23:12

5-Jan-08 23:12

And you are right!
Big Grin | :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Eytukan5-Jan-08 5:25

Eytukan

5-Jan-08 5:25

Hello George, nice to see you again. But this time I've got a question for you. Straight to you. Why do are you acting 'quick'-judgemental before someone could actually reply you fully? Unsure | :~

See here[^]
And I've seen many times , anybody who replies to your thread gets a 3 vote. Immediately. Is it a token of acknowledgment to say that you've read the message? Smile | :)

. I'm really not hurt by that but I'm finding it funny! Why do you do that?

OK,. what country just started work for the day ? The ASP.NET forum is flooded with retarded questions. -Christian Graus

Best wishes to Rexx[^]

pierre_ribery5-Jan-08 11:53

pierre_ribery

5-Jan-08 11:53

In a case like this you should initialize both a and b to 0 before the try clause. You cannot delete a or b at this stage, I assume you will need to use them later, or what was the purpose of allocating them?

int* a = NULL;
int* b = NULL;

try {
a = new int [N];
b = new int [M];
} catch (bad_alloc)
{
// Tell the user if a or b failed...

}

// Do some stuff on a or b

// Now delete if they are allocated
if(a)
delete a[];
if (b)
delete b[];

Thanks!

George_George6-Jan-08 2:42

6-Jan-08 2:42

Thanks pierre_ribery,

I want to confirm with you that your point is we need to delete a or b if they are successful allocated, even if bad_alloc happens (may be caused by other statements), right?

regards,
George

pierre_ribery6-Jan-08 9:58

pierre_ribery

6-Jan-08 9:58

Yes that was exactly my point!

If you have allocated memory, then you have to delete it. Therefore it is vital to initialize your pointers to 0 before using them.

Cheers,

Pierre

George_George6-Jan-08 20:43

6-Jan-08 20:43

Thanks for your advice, Pierre!

regards,
George

Hamid_RT5-Jan-08 18:04

Hamid_RT

5-Jan-08 18:04

Why you didnt use like this code
try
{
int * a= new int[N];
int * b= new int[M];
}
catch (bad_alloc&)
{
cout <<"Error allocating memory!";
}