Stack overflow visual C++, potentially array size?

Question

As far as I know, this isn't caused by an infinite recursion.

The program functioned correctly with smaller arrays (it is an audio editor). Now I have increased functionality to allow for larger arrays (up to 5 minutes of audio, 26460000 pieces of 16bit data ~50mb).

Since increasing the array's size I am receiving stack overflow errors on one particular function, where it should reverse the playback of an input file by writing the array into a new array backwards, then overwriting the original array. I'm guessing as each array could be up to 50MB this may be where the problem lies:

//initialise temporary new array to place samples in
short signed int reverse_data[max_number_samples];  

for (i=0; i<track_samples; i++)
{  //puts data from sound_data into reverse_data backwards.
  reverse_data[(max_number_samples-1)-i]=sound_data[i];    
}

for (i=0; i<track_samples; i++)    
{     //now overwrites sound_data with the data in reverse_data
  sound_data[i]=reverse_data[i];
}

I'm fairly new to C++, and programming in general, and am unsure of what the errors I get during debug are really telling me.

Any help would be appreciated, I'm sure there's a simple enough solution (I've read stuff involving 'heaps' but I'm not confident of what a'heap' really is).

Are you sure reverse_data[(max_number_samples-1)-i] is correct? You are writing data only to the end part of the reverse_data array, but than you read them from the beginning. — Vlad
– Vlad, Commented May 10, 2012 at 15:07
ah, I didn't see this comment. You are correct, but then I used another loop to search for the start of the audio, and only write the data from the start of the audio to the end. Thanks a lot for your help! — holmes321
– holmes321, Commented May 10, 2012 at 15:34

Vlad · Accepted Answer · 2012-05-10 14:51:19Z

6

You should not allocate large data structures on stack, because the stack's size is bounded. Allocate it on heap.

Even better, you should avoid manual allocation and use std::vector, which will care for the memory allocation itself. As a bonus, you won't need to care about deallocation. (And this is the modern C++ way.)

By the way, if max_number_samples is big, you should perhaps allocate only as much as you need:

std::vector<short int> reverse_data(track_samples);

(the rest of your code stays as it is).

Edit:
Even better idea: you can reverse your array in place, without copying into an additional array! Just go from index 0 to the half size and swap the ith and (size - 1 - i)th items:

for (i=0; i < track_samples/2; i++)
{
    std::swap(sound_data[i], sound_data[track_samples-1-i]);
}

edited May 10, 2012 at 14:51

answered May 10, 2012 at 14:45

Vlad

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8 Comments

Adriano Repetti Over a year ago

+1 ...and do not use recursion for such large amount of data!

holmes321 Over a year ago

Ah thanks, so the issue lies in the size of the arrays, as i expected! How would I initialise my arrays on heap, rather than stack?

Robᵩ Over a year ago

Re: "allocate only as much as you need": If max_number_samples if bigger than track_samples, then reverse_data[(max_number_samples-1)-i] will crash when i==0.

Robᵩ Over a year ago

Even betterer idea: std::reverse(&sound_data[0], &sound_data[track_samples]);

Vlad Over a year ago

@Rob: I assume it's a mistake in the OP's code: he wanted actually track_samples instead of max_number_samples.

|

Community · Accepted Answer · 2017-05-23 12:27:57Z

3

As Vlad pointed out, don't allocate 50MB on the stack.

But, the point is moot because you don't need to allocate any data. Try replacing your entire code fragment with a single call to std::reverse:

std::reverse(&sound_data[0], &sound_data[track_samples]);

Postscript: Don't forget to #include <algorithm>.

edited May 23, 2017 at 12:27

CommunityBot

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answered May 10, 2012 at 14:59

Robᵩ

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