C / C++ / MFC

Re: A Question about "__STDC__ ".

30-Aug-02 4:16

George Ma wrote:
Or the system will automatically add the setup of the macro to the source code?

'The system' isn't going to add the macro to sourc code. It will be predefined given the conditions described in MSDN. You can use the macro for preprocessor directives like #ifdef.

Tomasz Sowinski -- http://www.shooltz.com

Free your mind and your ass will follow.

George Ma30-Aug-02 18:44

George Ma

30-Aug-02 18:44

Thanks, Tomasz pal!

I think the macro is defined at the compling time,
am I correct?

Cheers,
George

CFile::Open fails

Janine30-Aug-02 1:20

Janine

30-Aug-02 1:20

Hello,

This might be a stupid question Blush | :O

. I'm trying to save and load settings in my program using CFileDialog. The problem is that opening the file I've saved fails most of the times, but not always. I'm assuming that it is because of a sharing violation, because CFileException gets a value 0xb, which means CFileException::sharingViolation. Please correct me if I'm wrong. lOsError got a value 0x20, but I can't find what that means.

So my question is, why does'nt the opening succeed? If it's because of sharing violation, what might be causing it? Not closing the file last time it was used might be, but I think it's something else, because opening fails randomly, like if I try to open it two times a row, the first trying fails and the next one succeeds.

Here's how I'm trying to do it:

void SettingsDlg::OnLoadButton() 
{
	UpdateData();
	CString cstrFileName;
	CFileDialog FileDlg(TRUE,	/* Make a open dialog box. */
			"cnf",	/* Default file name extension. */
			NULL,	/* No default filename. */
			OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT | OFN_NOCHANGEDIR,
			"Configuration files (*.cnf)|*.cnf|All files (*.*)|*.*||");

	if ( FileDlg.DoModal() == IDOK )
	{
		cstrFileName = FileDlg.GetPathName();

		/* Create a new file and open it. */
		CFile* pFile = new CFile();
		ASSERT (pFile != NULL);

		CFileException *pExc = new CFileException(TRUE);

		if ( !pFile->Open(cstrFileName, CFile::modeRead | CFile::shareExclusive, pExc) )
		{
			MessageBox("Error: Unable to open the file.");
			delete pFile;
			pFile = 0;
			return;
		}
		
		bool bReading = true;	/* We'll read. */
		CArchive* pArchive = NULL;
		
		try
		{
			pFile->SeekToBegin();
			UINT uMode = (bReading ? CArchive::load : CArchive::store);
			pArchive = new CArchive (pFile, CArchive::load);
			ASSERT (pArchive != NULL);
		}
		catch (...)
		{
			MessageBox("Error: Unable to read from the file");
			pFile->Close();
			delete pFile;
			pFile = 0;
			return;
		}

		Serialize(*pArchive);
		
		UpdateData(FALSE);

		delete pArchive;
		pArchive = 0;

		pFile->Close();

		delete pFile;
		pFile = 0;
	}
		
}

Please, help me
-Janetta

Tomasz Sowinski30-Aug-02 1:36

30-Aug-02 1:36

The error codes you've posted are indeed related to sharing violation - some other process has the file open, and you're trying to access the exclusive access to file (CFile::shareExclusive flag does this).

You may check www.sysinternals.com[^] and download their 'Handle' utility which displays information about open files.

On the other hand, you may just drop 'shareExclusive' flag.

BTW: why on Earth are you allocating your CFile and CArchive objects on the heap? You can just use local variables.

Tomasz Sowinski -- http://www.shooltz.com

Free your mind and your ass will follow.

Janine30-Aug-02 1:37

Janine

30-Aug-02 1:37

Tomasz Sowinski wrote:
On the other hand, you may just drop 'shareExclusive' flag.

I'm using that already, or am I doing it in a wrong way? It's used like this: if ( !pFile->Open(cstrFileName, CFile::modeRead | CFile::shareExclusive, pExc) )

I'll check the address you gave.

Thanks,
-Janetta

Tomasz Sowinski30-Aug-02 1:43

30-Aug-02 1:43

Sorry - I wasn't too clear. By dropping I meant removing the flag and using CFile::modeRead without shareExclusive or modeRead with shareDenyNone.

Tomasz Sowinski -- http://www.shooltz.com

Free your mind and your ass will follow.

Re: Scripting for Applications

Janine30-Aug-02 2:03

Janine

30-Aug-02 2:03

Ok, now I understood. And it helped. I'll go through the link later anyway, it seemed interesting.

Thanks.

-Janetta

Michael P Butler30-Aug-02 1:14

Michael P Butler

30-Aug-02 1:14

Search MSDN for IActiveScript and IActiveScriptSite.

This should give you a starting point for including Windows Scripting. There is a very good article by Don Box on MSDN too. (I haven't got a link to hand but it should come up in your search)

Michael Smile | :)

Programming is great. First they pay you to introduce bugs into software. Then they pay you to remove them again.

Re: Scripting for Applications

Pavel Klocek30-Aug-02 1:38

Pavel Klocek

30-Aug-02 1:38

You can use windows scripting - see how to do it with ATL.
If you don't want to use COM, see www.python.org.

Sonork 100.15206;PavelK

Re: Scripting for Applications

Ravi Bhavnani30-Aug-02 8:13

Ravi Bhavnani

30-Aug-02 8:13

Tcl/TK is perfect for this kind of stuff!

/ravi

Let's put "civil" back in "civilization"
http://www.ravib.com
ravib@ravib.com

min-max values

Zizilamoroso30-Aug-02 0:58

Zizilamoroso

30-Aug-02 0:58

Easy question Wink | ;-)

Where (header-file) can I find the minimum and maximum ranges for all the types in c++? Something like DOUBLE_MAX or INT_MIN ...

[VISUAL STUDIO 6.0] [MFC] [WIN98/2]

Bluute tette! Dead | X|

Tomasz Sowinski30-Aug-02 1:06

30-Aug-02 1:06

limits.h for integers and float.h for floating point numbers.

Tomasz Sowinski -- http://www.shooltz.com

Free your mind and your ass will follow.

markkuk30-Aug-02 1:16

markkuk

30-Aug-02 1:16

That's the C solution, but in C++ you can use the numeric_limits class defined in <limits>. for example:

#include <limits>
using namespace std;
// when you need a limit, use:
numeric_limits<int>::min();
numeric_limits<float>::max();
//etc...

Tomasz Sowinski30-Aug-02 1:29

30-Aug-02 1:29

markkuk wrote:
That's the C solution, but in C++ you can use the numeric_limits class defined in <limits>.

Good point. But I have to admit that I hate to type std::numeric_limits<int>::max() Smile | :)

Tomasz Sowinski -- http://www.shooltz.com

Free your mind and your ass will follow.

Zizilamoroso30-Aug-02 3:41

Zizilamoroso

30-Aug-02 3:41

INT_MAX is indeed much shorter Wink | ;-)

tnx!

[VISUAL STUDIO 6.0] [MFC] [WIN98/2]

Bluute tette! Dead | X|

Memory leakages

Anonymous30-Aug-02 0:56

Anonymous

30-Aug-02 0:56

I've seen many good articles here at CP, and below many articles, a famous comment is given that this code has memory leakage.

Can any one explain me how can we check that our application is causing memory leakages. I had idea that main cause of memory leakage is dynamic memory allocation using new and then not using delete. But IMHO this is not always true. So someone please tell me what is memory leakage, what are its causes and how can we determine that our application executable is causing memory leakage.

Re: Memory leakages

Tomasz Sowinski30-Aug-02 1:09