double free or corruption (fasttop) error

Question

So I'm implementing a heap using a resizable array and I keep getting this error every time it reallocates memory. The problem is with realloc ..I just can't figure out what's wrong with it. Here is the insert function:

void* insert (data_t *data, int room, long wake) {
 if(data->size+1 == data->arraySize){
    data->arraySize *= 2;
    long l = (long)data->arraySize;
    int* tempOne = realloc(data->heapElemOne, data->arraySize*sizeof(int));

    long* tempTwo = realloc(data->heapElemTwo, l*sizeof(long));

    if ( tempOne != NULL &&tempTwo !=NULL){ //realloc was
        data->heapElemOne = tempOne;
        data->heapElemTwo = tempTwo;
    }
    else{ //there was an error
        printf("Error allocating memory!\n");
        free(data->heapElemOne);
        free(data->heapElemTwo);
        return;
    }

  }
  data->size++;
  int now = data->size;

  /*Adjust its position*/
  if(data->size >0){

    while(data->heapElemTwo[now/2] > wake && ((now/2)!=0))
    {
            data->heapElemTwo[now] = data->heapElemTwo[now/2];
            data->heapElemOne[now] = data->heapElemOne[now/2];
            now /= 2;
    }
  }

  data->heapElemTwo[now] = wake;
  data->heapElemOne[now] = room;`

And Here is part of the main:

int main(int argc, char *argv[]){
    pthread_t r, c;
    data_t data;
    data.arraySize = 2;
    data.size = 0;
    long l = (long)data.arraySize;
    data.heapElemOne = malloc(data.arraySize * sizeof(int));
    data.heapElemTwo = malloc(l * sizeof(long));

Here's data_t declaration:

typedef struct{
    int arraySize;
    int* heapElemOne;
    long* heapElemTwo;
    int size;
    int number;
    pthread_mutex_t mutex;
    pthread_cond_t more;
}data_t;

It relocated the memory to 4 but when it's changing it to 8 it gives an error. Been at it for ages and just can't figure it out -_- Thanks in advance!

Could it be that in every call to malloc() and realloc() you want to multiply the number of elements to be allocated by sizeof( int ) or sizeof( long ) depending on the type of data you store? — ua2b
Post post the declaration of data_t. It sounds like you have a pointer & int reference problem. — David C. Rankin

Unknown Unknown · Accepted Answer · 2014-12-04T06:49:26

malloc(data.arraySize)

This and all other calls to malloc and realloc are wrong. You want

malloc(data.arraySize * sizeof(int))

or, respectively,

malloc(data.arraySize * sizeof(long))

according to your element type. malloc and friends accept allocation size in bytes, and ints and longs are normally larger than one byte. So your arrays are allocated too short, and you are getting buffer overruns.

double free or corruption (fasttop) error

3 Answers