memory managment problem; higher dimensional array doesn't delete

qanopus · 06-15-2005, 07:22 AM

Hello

could someone tell me whats wrong with the following code;

Code:

int main()
{

  int i,j;
  int sizeXY=100;
  int sizeZ=50;
  float ***Image;

  Image = new float **[sizeXY];

  for(i=0;i<=sizeXY;i++)
  {
          Image[i] = new float *[sizeXY];
          for(j=0;j<=sizeXY;j++)
          {
			Image[i][j] = new float[sizeZ];
           }
  }

  delete Image;

}

I set the export MALLOC_CHECK_ to '1';

Code:

export MALLOC_CHECK_=1

But ruunig this code gives me;

Code:

sohail@thabox:~/docs/tustuff/BEP/cpp/threeD$ ./prog.exe
malloc: using debugging hooks
*** glibc detected *** free(): invalid pointer: 0x0804c050 ***
sohail@thabox:~/docs/tustuff/BEP/cpp/threeD$

Whats going on??? Apparently, something is going wrong when freeing the used memory.

qanopus · 06-15-2005, 07:27 AM

Btw; I tried doing

Code:

delete [] Image;

But it gives me the same thing.

Doing something like

Code:

delete [][] Image;

doesn't even compile

qanopus · 06-15-2005, 07:39 AM

Okey, i'v made some progress. I have changed the code to;

Code:

int main()
{

  int i,j;
  int sizeXY=100;
  int sizeZ=50;
  float ***Image;

  Image = new float **[sizeXY];

  for(i=0;i<=sizeXY-1;i++)
  {
          Image[i] = new float *[sizeXY];
          for(j=0;j<=sizeXY-1;j++)
          {
			Image[i][j] = new float[sizeZ];
           }
  }

  delete Image;

}

But then I want to check for memory leaks;

Code:

sohail@thabox:~/docs/tustuff/BEP/cpp/threeD$ free
malloc: using debugging hooks
             total       used       free     shared    buffers     cached
Mem:        385464     299264      86200          0      23708     173696
-/+ buffers/cache:     101860     283604
Swap:       497972          0     497972
sohail@thabox:~/docs/tustuff/BEP/cpp/threeD$ make test
malloc: using debugging hooks
c++ main.cpp -o prog.exe -lgsl -lgslcblas -lm -O2
malloc: using debugging hooks
malloc: using debugging hooks
malloc: using debugging hooks
malloc: using debugging hooks
malloc: using debugging hooks
sohail@thabox:~/docs/tustuff/BEP/cpp/threeD$ ./prog.exe
malloc: using debugging hooks
sohail@thabox:~/docs/tustuff/BEP/cpp/threeD$ free
malloc: using debugging hooks
             total       used       free     shared    buffers     cached
Mem:        385464     299480      85984          0      23880     173660
-/+ buffers/cache:     101940     283524
Swap:       497972          0     497972
sohail@thabox:~/docs/tustuff/BEP/cpp/threeD$

as you can see, I have a memory leak (llok at the free memory before and after running the program.)

But the program runs without error :-)

jonaskoelker · 06-15-2005, 08:49 AM

You need to delete[] everything allocated with new[].

(pseudo-C++)

Code:

for(i) {
    for(j) delete [] array[i][j];
    delete [] array[i];
}
delete [] array;

Quote:

as you can see, I have a memory leak (llok at the free memory before and after running the program.)

I think the kernel would see that your process has finished and collect all its virtual memory--but you may have been faster than it.

Also, memory usage generally fluctuates on a desktop machine.

But I think you're right you're having a leak--when you []-allocate something, the allocator has to store the size (in order to call the correct number of destructors), and the size doesn't get freed when you delete (as opposed to delete []).

hth --Jonas

qanopus · 06-15-2005, 10:44 AM

Thanks dude!

jonaskoelker · 06-15-2005, 04:18 PM

Quote:

Thanks dude!

You're welcome.

--Jonas