c++ segFault issue

Question

I'm trying to do a program that creates various filters through webcam feed and ran into some issues with BLOB-analysis and some other.

I'm getting segFault everytime I activate my grassfire function. Here's the code for my grassfire function:

void testApp::grassFire(int mask_Y, int mask_X, unsigned char labelCnt)
{
    blobArray[mask_Y * camWidth + mask_X] = labelCnt;
    if (mask_X + 1 <= camWidth - 1 && blobArray[mask_Y * camWidth + mask_X + 1] == 0)
       grassFire(mask_Y, mask_X + 1, labelCnt);
    if (mask_Y + 1 <= camHeight - 1 && blobArray[(mask_Y + 1) * camWidth + mask_X] == 0)
       grassFire(mask_Y + 1, mask_X, labelCnt);
    if (mask_X - 1 >= 0 && blobArray[mask_Y * camWidth + mask_X - 1] == 0)
       grassFire(mask_Y, mask_X - 1, labelCnt);
    if (mask_Y - 1 >= 0 && blobArray[(mask_Y - 1) * camWidth + mask_X] == 0)
       grassFire(mask_Y - 1, mask_X, labelCnt);
}

And how it is called is by a switch case that runs every frame This means it gets called every frame update

The function itself is declared outside any other scope.

I know it is a really heavy filter and it might be using a lot of memory, but compared to some of the other filters, it's not that bad, so I cannot figure out why i get the segFault.

I also get the segFault on another filter, that shouldn't be that memory usage demanding. I'm using openframeworks in codeblocks on win 7.

score 2 · Accepted Answer · answered Jan 05 '13 at 21:43

2

It doesn't look like you can read/write paste the end of your blobArray since you do some checking, so it means you're the victim of a stack overflow.

You should use a debugger and run a backtrace, that many calls cannot hide.

answered Jan 05 '13 at 21:43

cmc

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score 0 · Answer 2 · edited May 23 '17 at 12:18

0

If you have a lot of array values of 0, you're probably getting a stack overflow due to the heavily recursive nature of the function. I'd suggest trying an iterative flood fill algorithm instead and see if that fixes the problem.

edited May 23 '17 at 12:18

Community

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answered Jan 05 '13 at 21:39

Adam Rosenfield

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score 0 · Answer 3 · answered Jan 14 '13 at 19:52

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I would instrument the application with valgrind. Valgrind will show a stack trace of where the segmentation fault occurred.

answered Jan 14 '13 at 19:52

Vandhunden

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c++ segFault issue

3 Answers3