c - Why am I getting a segfault here? -

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code split data training / test subsets below. note data_points 1 long vector of size items*attr, , data_labels vector of size items.

int split_data(int items, int attr, double *data_points, int *data_labels, double **split_train_points, int **split_train_labels, double **split_test_points, int **split_test_labels) {   srand(time(null));   int i, j;   double temp0, temp1;   double sorter[items][2];    *split_train_points = malloc(floor(split_prop*items * attr) * sizeof(double));   *split_train_labels = malloc(floor(split_prop*items       ) * sizeof(int));    *split_test_points  = malloc(ceil((1-split_prop)*items * attr) * sizeof(double));   *split_test_labels  = malloc(ceil((1-split_prop)*items       ) * sizeof(int));    // create 2d array element number in 1 column , random number in other   (i = 0; < items; i++) {       sorter[i][0] = i;       sorter[i][1] = rand() / (double)rand_max;   }    // sort random number column   (i = items-1; > 0; i--) {     (j = 1; j <= i; j++) {       if (sorter[j-1][1] > sorter[j][1]) {         temp0 = sorter[j-1][0];         temp1 = sorter[j-1][1];          sorter[j-1][0] = sorter[j][0];         sorter[j-1][1] = sorter[j][1];          sorter[j][0] = temp0;         sorter[j][1] = temp1;       }     }   }    int cutoff = floor(split_prop*items);   int element = 0;   // have bunch of indices in random order.  select first 70% store our split_train datasets   (i = 0; < cutoff; i++) {     element = (int)sorter[i][0];     *split_train_labels[i] = data_labels[element];     printf("success!\n");     (j = 0; j < attr; j++) {       printf("j: %d, data_points_element: %d\n",j,attr*element+j);        //segfault occurs here when j=4 every time element value changes due randomness       *split_train_points[attr*i+j] = data_points[attr*element+j];       printf("j out! %d\n",j);     }   }     (i = cutoff; < items; i++) {     *split_train_labels[i - cutoff] = data_labels[(int)sorter[i][0]];      (j = 0; j < attr; j++) {       *split_train_points[attr*(i-cutoff)+j] = data_points[attr*(int)sorter[i][0]+j];     }   }      return 0; }

as noted in code, segfault occurs @ same line, @ j=4, though "element" random number.

my guess it's because expression *split_train_labels[i] doesn't mean think means. compiler same *(split_train_labels[i]), mean (*split_train_labels)[i]. have problem in multiple places.

array indexing has higher precedence pointer dereference.


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