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Ann66 wrote: I had the following code to close my dialog application when ESC key is pressed.
Doesn't the Esc key do this by default?
"Take only what you need and leave the land as you found it." - Native American Proverb
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I have an OnPaint function and it's being called over and over and after a while, it throws a resource exception by simply saying:
A required resource was unavailable.
I have no idea what that means beyond what it says but it's happening sometime in the OnPaint function after it's run a couple thousand times. I only get the "CPaintDC dc(this);" at the top of the try block (to catch exceptions) and then I draw or not draw with if statements later. Am I allocating the drawing context without deallocating it, do I need to release the 'dc' variable or something to the system?
Under the CPaintDC constructor, it says this as a remark:
An exception (of type CResourceException) is thrown if the Windows GetDC call fails. A device context may not be available if Windows has already allocated all of its available device contexts. Your application competes for the five common display contexts available at any given time under Windows.
Is that affecting me? If so, how I do rectify this?
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It sounds to me like your paint handler is leaking resources. Could you post the code ? Do you clean up the brushes/bitmaps/DCs etc that you use ?
Christian Graus - Microsoft MVP - C++
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The code is complex, but here's the short of it:
try {<br />
CPaintDC dc(this);<br />
if ((thread == NULL) && (files != NULL)) {<br />
dc.Rectangle(x, y, x + 300, y + nTextHeight + 4);<br />
COLORREF OldColor = dc.SetTextColor (RGB(192, 192, 192));<br />
dc.SelectObject (new CBrush(RGB(192, 192, 192)));<br />
sMsg.Format("%s, %s", obj->GetName(), obj->GetStringFilesize());<br />
dc.TextOut(x + 2, y + 2, (LPCTSTR) sMsg);<br />
dc.SetTextColor(OldColor);<br />
dc.SelectObject (new CBrush (RGB(255, 255, 255)));<br />
}<br />
<2 more sections like the above exist with different if statement tests><br />
} catch (CResourceException * e) {<br />
e->Delete();<br />
thread->SuspendThread();<br />
char * lpszMessage = new char[128];<br />
e->GetErrorMessage(lpszMessage, 128, NULL);<br />
MessageBox(lpszMessage, "Critical Error", MB_ICONSTOP);<br />
delete[] lpszMessage;<br />
thread->ResumeThread();<br />
}
That's the gist (and most complex) part of it. I have 3 blocks like the if statement above, the first two are rarely used, but the third is heavily used when a particular thread is running. The heavily used if statement is similar in layout to the above but it draws a text element and pie, both correspond to a progress display of the thread the code mentions. I was handling the CBrush's by new'ing and delete'ing them manually but it threw runtime errors when delete'ing the CBrush's, it said a "pure virtual function call" or something like that. I don't do any clean up, I just get the dc from CPaintDC and then draw, that's it. I figured I didn't need to deallocate the drawing context because I was using it in this method, instead of using a handle to a drawing context with GetDC/ReleaseDC.
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LighthouseJ wrote: dc.SelectObject (new CBrush(RGB(192, 192, 192)));
This is a resource leak. you need to create a brush as a variable, and when you call selectobject, you need to grab the brush it returns. Then you need to restore the original brush, and destroy the brush you created.
LighthouseJ wrote: dc.SelectObject (new CBrush (RGB(255, 255, 255)));
Ditto. I assume this is supposed to restore the original brush color, but you need to actually restore the original brush.
Christian Graus - Microsoft MVP - C++
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I actually did that originally but I got the aforementioned error because I was trying to free memory from another threads heap. I changed it like below and no error shows up so I guess it's cleared up but I have to clean up the code more because it was opened up to try and fix this with other methods.
CBrush * grey = new CBrush (RGB(192, 192, 192));<br />
CBrush * black = new CBrush (RGB(255, 255, 255));<br />
dc.SelectObject (grey);<br />
<br />
< drawing done here ><br />
<br />
dc.SelectObject(black);<br />
<br />
delete grey;<br />
delete black;
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LighthouseJ wrote: I actually did that originally but I got the aforementioned error because I was trying to free memory from another threads heap.
Well, it's the way it needs to be done, you need to work out those threading issues, I guess..
LighthouseJ wrote: CBrush * grey = new CBrush (RGB(192, 192, 192));
CBrush * black = new CBrush (RGB(255, 255, 255));
dc.SelectObject (grey);
< drawing done here >
dc.SelectObject(black);
delete grey;
delete black;
This is wrong.
CBrush * grey = new CBrush (RGB(192, 192, 192));
CBrush * black = dc.SelectObject (grey);
< drawing done here >
dc.SelectObject(black);
delete grey;
You need to grab the brush that SelectObject returns, and put it back when you're done.
Christian Graus - Microsoft MVP - C++
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I was trying to capture the outgoing brush but when I delete it, I got the error saying the memory I was deallocating wasn't mine. So, I just don't delete the black brush? Isn't that leaking memory?
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LighthouseJ wrote: I was trying to capture the outgoing brush but when I delete it, I got the error saying the memory I was deallocating wasn't mine.
Correct. You can't delete it, you need to select it back into the DC in order to avoid a leak.
LighthouseJ wrote: So, I just don't delete the black brush? Isn't that leaking memory?
No, because you don't create a black brush, and because the brush in question is left in the control of the DC, as it was at the start.
Christian Graus - Microsoft MVP - C++
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Have a look at CDC::SaveDC() ( There is also an excellent article by Joe Newcomer on this site about SaveDC(), look it up ) and also why not just use local GDI objects that go out of scope when you are done with them? saves having to mess around with new and delete.
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
"Obviously ??? You're definitely a superstar!!!" - mYkel - 21 Jun '04
"There's not enough blatant self-congratulatory backslapping in the world today..." - HumblePie - 21 Jun '05
Within you lies the power for good - Use it!
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I'll read that tonight. I haven't optimized the program for space and efficiency yet but one thing I did was to put the grey brush into the child view to be created once on construction, then used repeatedly, and deleted on deconstruction. I also have to figure out a better flow to my program but that's on my shoulders. I'm trying to optimize drawing because it's definitely the slowest part of my program.
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I know how to do that in visual c++ NET but I have to use visual c++ 6.0 only. so how can I convert byte array to image(or binary) that will insert data to sql database.
STDMETHODIMP CModels::AddPicture(IUnknown* pIUnkConnection , byte* byteImage)
{
_ConnectionPtr spIConnection;
CConnection connection;
connection.GetConnectionToDB(pIUnkConnection, &spIConnection);
_bstr_t bstrCommand = "INSERT INTO MODEL VALUES ('" First Picture "', "', ?????(byteImage)how can I can convert byte array to image???)";
THROW_COM_ERROR(spIConnection->Execute(bstrCommand, NULL, adExecuteNoRecords));
bytes[] convert to image(binary)
Remember I cant use C++ .NET at all
use Visual c++ 6.0 only
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Using Visual C++ 6, running some C++ code which allocates & frees some memory, usually if I've got any problems with unallocated/unfreed memory I'll get access violations, exceptions, but this time I'm getting a heap error I've never seen before:
HEAP : dedicated (0000) free list element 6fa9ae8 is marked busy
What's the difference between this and an access violation / exception?
I think it means I'm running of of heap space, as it can happens at any memory allocation in my code, but it doesn't look that way from the amount of memory my program is using?
Any tips of finding out the cause of this?
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Tam987654321 wrote: Using Visual C++ 6, running some C++ code which allocates & frees some memory...
Are you using the new and delete operators?
"Take only what you need and leave the land as you found it." - Native American Proverb
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Thanks for trying to help, I managed to fix my code.
It was new & delete operators I was using, the problem was I was overrunning a buffer.
I discovered the cause by using _heapchk to check the status of the heap, I took the code from the following link and put it at different parts of my code to find out when the heap was getting corrupted.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_crt__heapchk.asp
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Hi,
I am getting boolean value from store procedure.When flag is set, it fill value 255 otherwise 0. It should be 1/0. When i tried to declared varaible type bool no data is coming and it is showing garbage.Can you please help me.
Thank
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simple:
suppose c is what you get from the stored proc and b is the boolean you want.
just do this: b = c & 1;
cast (c & 1) to bool if needed
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I believe this is the correct result as VARIANT_TRUE is defined as -1, VARIANT_FALSE is 0.
What database are you using?
John
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Thank you for your reply. I think you are right, for interger it is showing -1 for set flag. I am using SQL server.
~Pankaj
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When exactly is the file mapped into memory updated on the disk? I thought it will be updated as and when it is updated in the memory, but the documentation of UnMapViewOfFile says "If the function succeeds, the return value is nonzero, and all dirty pages within the specified range are written \"lazily\" to disk" which means the file will be written to the disk only when UnMapViewofFile is called.
Can someone clarify? Thanks.
thanks
/f
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This is saying tht UnMapViewOfFile will trigger a lazy write, but the OS may write this data at any time. For performance reasons, however, it will tend to defer this. If you must write the data, just call FlushViewOfFile().
Note, however, that by default this still does a lazy write as do all disk writes (by default.) In practice the data will be written within very few milliseconds. And before you panic, note that your hard disk has a cache and is essentially doing the same thing.
If you want more immediate writes, you must use the FILE_FLAG_WRITE_THROUGH flag when you open the file (and follow the guidelines of using that flag.)
Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke
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I posted something similar to this earlier, but I think I'm getting closer to the problem.
I wrote my own class, CFAFRecord, that is a derivative of CObject. When someone presses the button, I do something similar to
my_ObjectArray.SetSize(10);
CFAFRecord my_Record;
my_Record.name = m_Name;
my_Record.address = m_Address;
my_ObjectArray.SetAt(0, &my_Record);
my_ObjectArray in the example is a CObArray that is a member variable of my dialog. Later, when I try to access, I try
CFAFRecord * my_Record = *(CFAFRecord *)my_ObjectArray.GetAt(0);
m_Name = (*my_Record).GetName();
When I try that last line, I get an access violation, looks like a memory access error. I think I'm handling the memory wrong somewhere, maybe in the first functiion, when I use the SetAt, I pass the pointer to my_Record and my_Record is probably destoyed at the end of the function. If that's the case, how can I can I fix this?
Danny
The stupidity of others amazes me!
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Thought so, you have now posted the offending code.
my_ObjectArray.SetSize(10);
CFAFRecord my_Record;
my_Record.name = m_Name;
my_Record.address = m_Address;
my_ObjectArray.SetAt(0, &my_Record); my_Record goes out of scope and is destroyed, so that the address that is stored in my_ObjectArray now points to useless memory, thus your access violations.
"You're obviously a superstar." - Christian Graus about me - 12 Feb '03
"Obviously ??? You're definitely a superstar!!!" - mYkel - 21 Jun '04
"There's not enough blatant self-congratulatory backslapping in the world today..." - HumblePie - 21 Jun '05
Within you lies the power for good - Use it!
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bugDanny wrote: CFAFRecord my_Record;
Should be:
CFAFRecord *my_Record = new CFAFRecord;
...
my_ObjectArray.SetAt(0, my_Record);
"Take only what you need and leave the land as you found it." - Native American Proverb
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Thank you.
Danny
The stupidity of others amazes me!
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