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If you mean that base class have same values whenever an object of its child classes are made then yes same class have 'same instance'. But, it is false in the sense that each time an object is created, its new instance is created in memory. So, when you are creating the instance of a child class, its respective base class' instance is also created in memory. And if you are creating two instances of two child classes derived from same base class, then two different instances of base class are also getting created in memory against both child objects.
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An instance of a class is created when memory is allocated for the class.
In the code that you've shown, there is no instance created and no memory allocated.
Refer to the code snippet below -
class BaseClass
{
int base;
};
class ChildOne : public BaseClass
{
int childOne;
public ChildOne(){}
};
Class ChildTwo : public BaseClass
{
int childTwo;
public ChildTwo(){}
};
When an object of ChildOne is created, memory is allocated for int base; and int childOne;
When an object of ChildTwo is created, memory is allocated for int base; and int childTwo;
Here you can see that memory for int base; has been allocated twice, once for the instance of ChildOne and once for the instance of ChildTwo.
So base has separate memory and hence value for each instance.
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Hi,
I am using CreateDIBSection() function frequently in my code but sometimes it is failing.
The value of biWidth is around 6000, biHeight is 4000 and biBitCount is 24 in BITMAPINFOHEADER.
My doubt is on memory, can someone please tell how much meomory is consumed by each call of CreateDIBSection() considering the values which is mentioned earlier.
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How do you know it's failing? Do you get an exeception, error return, message ... ? Please provide proper details of exactly what code fails and what response you see.
Veni, vidi, abiit domum
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I am getting a NULL value in return and ppvBits is also NULL.
Actually sometimes one failure is there at some other place in code while allocating meomory where the i am getting windows error code 8.
So i thought that it could be related to memory which is getting consumed by each call to CreateDIBSection() function though i am calling DeleteObject() after using the bitmap.
Thanks
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Well you need to check the error code every time you get an error response and try to figure out why it is being given. Error code 8 says Not enough storage is available to process this command., so that is reasonably clear.
Veni, vidi, abiit domum
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Following is the code snipet
void create(const CSize& size)
{
initBitmapInfo(size);
mBitmap = ::CreateDIBSection(0,
getBitmapInfo(),
DIB_RGB_COLORS,
(LPVOID*) &mBits,
0,
sizeof(BITMAPINFOHEADER));
if (mBitmap == 0 || mBits == 0)
{
cout << "NcSurface::destroy()-------- mBitmap = " << mBitmap<< endl;
cout << "NcSurface::destroy()-------- mBits = " << mBits << endl;
cout << "NcSurface::destroy()-------- size.cx = " << size.cx << endl;
cout << "NcSurface::destroy()-------- size.cy = " << size.cy << endl;
ErrorInstance::instance()->throwError(__FILE__, __LINE__, GdiException());
}
}
void initBitmapInfo(const CSize& size)
{
BITMAPINFO* bmi = getBitmapInfo();
CHECK(bmi != 0);
bmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi->bmiHeader.biWidth = size.cx;
bmi->bmiHeader.biHeight = size.cy;
bmi->bmiHeader.biPlanes = 1;
bmi->bmiHeader.biBitCount = 24;
bmi->bmiHeader.biCompression = BI_RGB;
bmi->bmiHeader.biSizeImage = 0;
bmi->bmiHeader.biXPelsPerMeter = 0;
bmi->bmiHeader.biYPelsPerMeter = 0;
bmi->bmiHeader.biClrUsed = 0;
bmi->bmiHeader.biClrImportant = 0;
}
size.cx = 6000 and size.cy = 4000
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In error situation the code mentioned in the if condition above is getting executed. This error i am getting while executing automated test case and that too very few times.
Basically this is comming when the sysetm run for few hours/days. So I want to know the memory usage of CreateDIBSection() to ensure that it is not craeting holes in memory as it is getting calle dfrequnently in my code.
Thanks
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ash_hdr wrote: So I want to know the memory usage of CreateDIBSection()
Task manager will show you the usage of your application. If it keeps growing then you know it's leaking memory.
Veni, vidi, abiit domum
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I already tried task manager to find the memory leak but not able to find it.
But it will be helpfull if i can get to know the memory which CreateDIBSection is consuming everytime it is getting called. Event though DeleteObject() is getting called at appropriate place but i just want to know the hole which is getting created in memory after each usage.
Thanks
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ash_hdr wrote: I already tried task manager to find the memory leak but not able to find it.
Task manager won'y help you find the leak, but it will give you an indication of the memory that is being used by your application, and whether it keeps growing all the time.
ash_hdr wrote: if i can get to know the memory which CreateDIBSection is consuming everytime it is getting called.
That information is not readily available as it is internal to Windows.
Veni, vidi, abiit domum
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Actually I tried all those things and event some tools also i tried but didn't get the expected results.
How much memory will the ppvBits takes in CreateDIBSection.
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ash_hdr wrote: How much memory will the ppvBits takes in CreateDIBSection.
No idea, but you could probably work it out by examining the documentation[^]
.
Veni, vidi, abiit domum
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What is the point of the initBitmapInfo function? It creates a (I assume new) BITMAPINFO structure, initialises it with some values, and then returns without doing anything with it. That looks like a memory leak to me, depending on what getBitmapInfo is doing.
Veni, vidi, abiit domum
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The variable which getBitmapINfo is getting a class member variable, so there is no memory leak there.
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That's certainly not obvious from the code, nor is it obvious that this is part of some class. I would hate to be the poor developer who has to maintain this.
Veni, vidi, abiit domum
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Sorry that's my fault. While pasting the code i removed that information.
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ash_hdr wrote: While pasting the code i removed that information.
Why? It really would help you much more to post the exact code that you have trouble with.
Veni, vidi, abiit domum
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The CreateDIBSection call looks fine to me except that the last parameter is ignored according to the docs so you could pass there a 0.
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But anyway this should not cause any issue. Is the height and width which i am passing is more and the bitmap is consuming a lot of memory? This function is getting called lot of times in my application.
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You can calculate the memory needed by the dibsection and you should be able to track the memory allocation in your program. Put in some diagnostic code: When this createdibsection fails then run the diagnostic code that gets the available free memory and so on. Getting the free memory may not be the best diagnostic as sometimes the OS lies (for many reasons) and the available memory may be available only as fragmented small pieces. maybe a good diagnostic could could try to perform a malloc with approximately the size of the image (maybe a bit more, for example twice the size of the image). If this malloc fails then you probably went out of available memory. Use your creativity, these were just some stupid things I would try first...
3*6000*4000 == 72000000 bytes ~ 72megs. If you allocate 72 megs chunks rapidly you can exhaust even 1 gig of memory quite quickly...
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Hi,
If you mean to say that if width = 6000 and height = 4000 and considering 3 bytes per pixel on every call createDIBSection is consuming 72 mega bytes then i feel this is the place which is causing memory fragmentation. Is my understanding correct?
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I'm not saying that memory fragmentation is the problem. I don't know what the problem is.  Let's try to find that out!
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I am asking about the calculation i.e 72 MB for each CreateDIBSection call.
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Rather than repeating the same question over and over, would it not be better if you acted on some of the advice you have been given? We do not know the exact amount of memory that is being used, and the best estimate is the one you have been given. It is up to you to do some logging/debugging of your application to find out what is actually happening when the code runs, and how much memory it is consuming.
Veni, vidi, abiit domum
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