Why is this leaking memory? (Pointer Array C)

Question

Gmorning SO-

valgrind says:

==9735== 24,976 bytes in 446 blocks are definitely lost in loss record 9 of 9
==9735==    at 0x100012362: malloc (vg_replace_malloc.c:266)
==9735==    by 0x1000016F2: interpolate (in ./a.out)
==9735==    by 0x100000CFA: main (in ./a.out)

Yikes. Here's my interpolate function:

void interpolate(PDouble* evaluated, int doubleCount){
int i, j, k;
int boxCount = 0;
int frameCount = 0;

for(i=0; i<doubleCount; i++){
  boxCount = evaluated[i]->first->numBoxes;
  frameCount = evaluated[i]->gap;
  evaluated[i]->changeMatrix = (int***)malloc(boxCount*sizeof(int**));

for(j=0; j < boxCount; j++){
  evaluated[i]->changeMatrix[j] = (int **)malloc(ATTR * sizeof(int*));

  for(k=0; k < ATTR; k++){
    evaluated[i]->changeMatrix[j][k] = (int*)malloc(sizeof(int)*frameCount);
    if(evaluated[i]->differenceMatrix[j][k] > 200 ||
       evaluated[i]->differenceMatrix[j][k] < -200){
      generateRotationSequence(evaluated[i]->changeMatrix[j][k],
                               evaluated[i]->first->boxes[j]->o,
                               evaluated[i]->second->boxes[j]->o,
                               frameCount);
    }
    else{
      evaluated[i]->changeMatrix[j][k] = (int*)malloc(sizeof(int)*frameCount);
      generateSequence(evaluated[i]->changeMatrix[j][k], 
                       evaluated[i]->differenceMatrix[j][k], frameCount);
    }
   }
  }
 }
}

But I have the C functions that free all the pointers for PDoubles. I can provide the code if needed, but is there anything glaring about this that would make it leak, or make pointers dangle?

Edit: Realized I was using a strange term in description. Also this time im adding my destructors

void killDouble(PDouble marked){
int i, j, k;
int gap = marked->gap;
for(i=0; i < marked->first->numBoxes; i++){
  for(j=0; j < ATTR; j++){
    free(marked->changeMatrix[i][j]);
  }
  free(marked->changeMatrix[i]);
  free(marked->differenceMatrix[i]);
}
for(i=0; i < gap; i++){
  killFrame(marked->intFrames[i]);
}
killFrame(marked->first);
killFrame(marked->second);
free(marked->changeMatrix);
free(marked->differenceMatrix);
free(marked->intFrames);
free(marked);
}

Daniel Fischer · Accepted Answer · 2012-06-11 16:01:33Z

5

You allocate evaluated[i]->changeMatrix[j][k]

evaluated[i]->changeMatrix[j][k] = (int*)malloc(sizeof(int)*frameCount);
if(evaluated[i]->differenceMatrix[j][k] > 200 ||
   evaluated[i]->differenceMatrix[j][k] < -200){
  generateRotationSequence(evaluated[i]->changeMatrix[j][k],
                           evaluated[i]->first->boxes[j]->o,
                           evaluated[i]->second->boxes[j]->o,
                           frameCount);
}
else{
  evaluated[i]->changeMatrix[j][k] = (int*)malloc(sizeof(int)*frameCount);

unconditionally and then again without freeing if the condition is not satisfied. That's your leak.

Since both allocations are exactly the same, you should remove the one in the else block, it is pointless.

edited Jun 11, 2012 at 16:01

answered Jun 11, 2012 at 15:53

Daniel Fischer

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3 Comments

SetSlapShot Over a year ago

Sorry I think I was leaving off something critical. I just added the function I call later on every "PDouble" in the program. Wouldn't that free it?

Daniel Fischer Over a year ago

No, when you call it, the pointer obtained from the first allocation is already lost. Since the allocation is exactly the same as the one before the if, remove it. Or just put a free(evaluated[i]->changeMatrix[j][k]); at the start of the else block.

SetSlapShot Over a year ago

Got it. Didn't even realize I was mallocing it out twice. Thank you!

Alessandro Pezzato · Accepted Answer · 2012-06-11 15:53:27Z

2

evaluated[i]->changeMatrix[j][k] = (int*)malloc(sizeof(int)*frameCount);

This is the leak. You allocate memory, but never free

answered Jun 11, 2012 at 15:53

Alessandro Pezzato

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