Memory leak or not memory leak?

[madric]

Hi!

I currently looking for memory leak in my application. After I found out one operation that seems to make a memory leak from the task manager, I decided to test one thing (since I know I can't trust the task manager information).

I created 3 small windows applications by using the project wizard of visual studio 2008, using default settings.

In the first application, I do nothing else, just run it - pretty simple.

In the second application, I just add at the end of the "InitInstance" member function of my class application the following lines:
BYTE **up_info = new BYTE *[80000];
for (int i=0; i<80000; i++) up_info[i] = new BYTE[512];
for (int i=0; i<80000; i++) delete[] up_info[i];
delete[] up_info;

In the third application, I did the same thing than for the second application with adding a loop on this memory allocation/deallocation a big number of time.

I believe that my code does not have memory leak. Tell me if I am wrong.
After the memory allocation/desallocation has been finished for each of the 3 applications, I checked the memory information through the Process Explorer application.
Here are the information:

Type of memory / First Application / Second Application / Third Application
Working set / 15,584 K / 19,180 K / 50,324 K
WS Private / 3,428 K / 7,020 K / 38,152 K
WS Shareable / 12,156 K / 12,160 K / 12,172 K
WS Shared / 10,912 K / 10,896 K / 10,912 K
Private Bytes / 4,632 K / 8,160 K / 39,408 K
Virtual Size / 118,644 K / 165,364 K / 197,748 K
Peak Private Bytes / 8,688 K / 47,580 K / 49,412 K
Peak Working set / 19,572 K / 55,896 K / 57,396 K

In case of the third application, the memory is increasing until stabilizing to a certain value. I stopped the loop when the memory usage was stable in the Task manager.

So here are my questions:
Since I truely believe that my code doesn't generate memory leaks, why does the private bytes has increased so much in the case of the third application?
How can I read all theses memory values to determine whether I have a memory leak or not?
During the loop of the third application, the number of page fault is increasing a lot. Why?

Thanks for you time,

madric

[cilu]

No, that code doesn't have memory leaks. If you want memory leak reports, use a specialized tool, not task manager or PE.

[madric]

So why the private bytes is over 38MB for the third application?
And what specialized tool should I use?

[anantwakode]

Hi,

check this.. !

http://www.softwareverify.com/cpp/memory/index.html



-Anant

[cilu]

So why the private bytes is over 38MB for the third application?
And what specialized tool should I use?

There are commercial tools and also free tools. I've used this Visual Leak Detector several times.

http://dmoulding.googlepages.com/vld
http://www.codeproject.com/KB/applic...kdetector.aspx

[madric]

ok thanks, I will look into those softwares.
But, just wonder...
There is no way to know how much memory my application has really allocated from all the statistics given from Process Explorer?

[Lindley]

You should think of the virtual memory footprint in PE as sort of an approximate "peak memory used at once" measure for the program. There's not a whole lot of reason for that to get smaller when actual usage decreases (although it sometimes may). Plus there are behind-the-scenes OS factors which may jiggle the numbers around a bit. So no, in exact terms, you can't rely on PE for much of anything except detecting whether you're leaking memory like a sieve.