C / C++ / MFC

6-Jul-04 9:46

subject. Please!
Thanks a lot in advance.

Johan Rosengren6-Jul-04 10:44

6-Jul-04 10:44

Rigid programming discipline.

If that is not enough, Boundschecker.

CherezZaboro6-Jul-04 11:40

6-Jul-04 11:40

You had to go out and type in that first remark, right? What if it's not my code? Cool | :cool:

"Boundschecker" - now I remember. D'Oh! | :doh:

Johan Rosengren6-Jul-04 21:05

6-Jul-04 21:05

inner wrote:
You had to go out and type in that first remark, right? What if it's not my code?

Of course I had Smile | :)

There is an almost religious belief in leak finding tools, garbage collectors etc. With stricter discipline, leaks are much less of a problem.

And even if the code is not yours, a global search for all instances of new, replacement of dynamically allocated stuff with static variables etc. will increase code quality - something that a memory leak tool will not - you'll only fix leaks, not bad memory usage. An example:

void SomeFunction()
{
  CSomething* obj = new CSomething;
  // code
}

Boundschecker will find that you never deallocate obj. The chances are big that you replace the code with:

void SomeFunction()
{
  CSomething* obj = new CSomething;
  // code
  delete obj;
}

No leak. So far, so good. Now, the next maintaining developer copies part of the code to another function, so:

void SomeOtherFunction()
{
  CSomething* obj = new CSomething;
  // other code
}

New leak. If you instead corrected the code from the beginning to:

void SomeFunction()
{
  CSomething obj;
  // code
}

you'll have less lines of code to analyze for the next maintainer, easier to find the necessary but risky dynamic allocations, and no temptations for the copy and paste brigade = higher quality code!

CherezZaboro7-Jul-04 3:32

7-Jul-04 3:32

I understand all that! Thanks!
In 8 years of programming I never had to use boundschecker! Heck, that's why I even forgot the name of it and asked here. Used to hear about it from people but I always was able to find/fix issues with just what VC has to offer.
Now about the new and replacing it. You don't suggest to not use pointers at all, do you? Plus some of the problems that come up are not even related (seemingly - excuse my spelling Blush | :O

) to our in house code as you described with different maintainers. Our code uses libraries from other vendors. And right now I'm having a problem with this:

<br />
Detected memory leaks!<br />
Dumping objects -><br />
{67} client block at 0x015B4CE8, subtype 0, 64 bytes long.<br />
a CDynLinkLibrary object at $015B4CE8, 64 bytes long<br />
{63} client block at 0x015B4A08, subtype 0, 64 bytes long.<br />
a CDynLinkLibrary object at $015B4A08, 64 bytes long<br />
{56} client block at 0x015B2E18, subtype 0, 64 bytes long.<br />
a CDynLinkLibrary object at $015B2E18, 64 bytes long<br />
Object dump complete.<br />

Of course the issue is probably in my code but it comes up as a leak of a MFC class. Now I would just like to see where exactly those objects are created. How else can I see when the process loads like 50 DLLs? Only 4 of them are mine and the leak is not in them.

Johan Rosengren7-Jul-04 3:52

7-Jul-04 3:52

inner wrote:
Now about the new and replacing it. You don't suggest to not use pointers at all, do you?

No, of course not. But it should be used sparingly, and with care. An example where new is necessary is in containers, where lots of objects are stuffed in vectors or CObArrays. But in this case, by creating a container wrapper class, where the dtor deletes all memory, you'll avoid possible leaks. Another rule of thumb that I've used with great success is always writing the deallocation code at the same time as the allocation.

inner wrote:
Of course the issue is probably in my code but it comes up as a leak of a MFC class. Now I would just like to see where exactly those objects are created. How else can I see when the process loads like 50 DLLs?

This might very well be because a dtor is not called, so it's not certain that Boundschecker or other tools will point out the real error.

But I'm a great fan of Boundschecker. That tool has saved lots of development time around the word! It shouldn't be difficult to be allowed to buy it, if you are in a situation where you can't decide such stuff yourself - running your application(s) through it, it will most likely earn its cost the first day, when leaks and GDI-losses are detected Smile | :)

CherezZaboro7-Jul-04 4:21

7-Jul-04 4:21

The thing about CDynLinkLibrary is that it's created like this, right? :

<br />
new CDynLinkLibrary(TrymfcdefDLL);<br />

Without assigning it to anything. And MFC knows to kill it when DLL is about to be unloaded, right?
And each MFC extension DLL has this, right? Well. In my DLLd dtors deffinitely get called. Cause I've replaced CDynLinkLibrary with my own CDynLinkLibrary derived class and ctor and dtor TRACE to output. So there are some other DLLs that have a problem I assume.
Confused | :confused:

Do you know by any chance if latest is compatible with VC6? Cause I still have my projects there. I want to go VC 7 but, our management doesn't like to take such steps in a hurry.
Mad | :mad:

Johan Rosengren7-Jul-04 4:53

Connecting to Oracle without a DSN

7-Jul-04 4:53

I don't know how CDynLinkLibraries are deleted, but if they register themselves to a global list, they will indeed be deleted automatically. It's easy to check, however. Put a breakpoint in one of the working DLL dtors, and look at the callstack when it is triggered. This will allow you to trace backwards, and might give an indication why the leaking ones don't get deleted.

As for Boundschecker, a quick check on the net shows that Boundschecker 7.1 supports MSVC++ 6.0. Personally, I won't upgrade to VC 7 until the clamour over how crappy it is in microsoft.public.vc.mfc dies down Smile | :)

subclassing in win32

Anonymous6-Jul-04 9:40

Anonymous

6-Jul-04 9:40

I'm trying to attach a bitmap to a button using subclassing in win32 vc++.Can anyone help

Re: subclassing in win32

palbano6-Jul-04 9:54

palbano

6-Jul-04 9:54

Anonymous wrote:
Can anyone help

That is very likely. However you must first accurately describe the problem.

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: subclassing in win32

David Crow6-Jul-04 10:02

David Crow

6-Jul-04 10:02

In addition to palbano's post, you might also want to provide the snippet of code that is not working. It'll make suggestions a lot more meaningful.

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

pankajdaga6-Jul-04 8:37

pankajdaga

6-Jul-04 8:37

Hi everyone,

I wanted to know about the connection string for connecting to an Oracle database that is not registered in the system DSN.

For example, for connecting to SQL Server I use:
"DRIVER={SQL Server};SERVER=xp01;UID=user;PWD=pass;APP=Generic32;DATABASE=SOMEDATABASE";

However, I cannot figure out the connection string for an Oracle database. I always have to use a DSN.

Can someone help me out with it?

Thanks,

Sincerely,

Pankaj

Without struggle, there is no progress

Re: Connecting to Oracle without a DSN

Michael P Butler6-Jul-04 8:43

Michael P Butler

6-Jul-04 8:43

This article[^] has an example connection string for most DBs including Oracle.

Michael

CP Blog [^]

Re: Connecting to Oracle without a DSN

pankajdaga6-Jul-04 11:27

pankajdaga

6-Jul-04 11:27

Perfect! Thanks a lot for pointing that one out.

CP is amazing Smile | :)

Sincerely,

Pankaj

Without struggle, there is no progress

variable question

Timothy Grabrian6-Jul-04 7:21

Timothy Grabrian

6-Jul-04 7:21

I should know this by now, but what variable is 16 bytes, and which one is 64 bits?

thanks

wWw.KruncherInc.com - My cool programs

Jeremy Falcon6-Jul-04 7:28

Jeremy Falcon

6-Jul-04 7:28

Do you mean 16 bytes or bits?

16-bit is a short int.

Are you looking for a 64-bit integer? If so, use __int64. Just remember it's Microsoft specific though.

Jeremy Falcon

Timothy Grabrian6-Jul-04 7:42

Timothy Grabrian

6-Jul-04 7:42

I'm trying to read the ".lnk" header, I found the specs here http://myfileformats.com/download.php?url=/files/shortcut.zip&id=5870&name=LNK

under "The File Header" Im looking at
offset 4h contents GUID of shortcut files
offset 1Ch contents Time 1
offset 24h contents Time 2
offset 2Ch Contents Time 3

wWw.KruncherInc.com - My cool programs

David Crow6-Jul-04 9:29

David Crow

6-Jul-04 9:29

I'm not exactly sure what you are asking.

offset 4h contents GUID of shortcut files is 24 bytes in length
offset 1Ch contents Time 1 is 8 bytes in length
offset 24h contents Time 2 is 8 bytes in length
offset 2Ch Contents Time 3 is presumably 8 bytes in length

A char is one byte. A short is 2 bytes. A long is 4 bytes. An int is the same size as the system word (4 bytes in 32-bit OSs).

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Timothy Grabrian6-Jul-04 14:55

Timothy Grabrian

6-Jul-04 14:55

LOL fine, what is a 64 bit int in C? Not platform specific?

Ryan Binns6-Jul-04 18:31

Ryan Binns

6-Jul-04 18:31

KingKruncher wrote:
what is a 64 bit int in C?

long long, but not all compilers support it.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"