I was trying to answer this question and after writing this code
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
int M =10;
int N =30;
int K = 10;
struct element {
int *i;
int *j;
int k;
};
struct element *create_structure();
void print_element(struct element *);
int compare (const void *, const void * );
void sort(struct element *); // changed the return value of sort
// to void as the argument will be changed directly because it is a
// pointer
int main()
{
srand(time(NULL));
struct element *lista;
lista=create_structure();
printf("\n--------- i --- j ---------\n\n");
print_element(lista);
printf("\n---------------------------\n");
sort(lista);
print_element(lista);
return 0;
}
struct element *create_structure()
{
int aux1=0,count=0;
struct element *structure;
// Changed the allocation of structure pointer
structure = (struct element *) malloc (sizeof(struct element));
structure->k=K;
structure->i= (int *)malloc(K*sizeof(int));
structure->j=(int *)malloc (K*sizeof(int));
for (count = 0; count < K; count ++)
{
aux1=rand()%N;
// we kept only the first aux1 and copied it in the two arrays
(structure->i)[count]=aux1;
(structure->j)[count]=aux1;
}
return (structure);
}
void print_element(struct element *lista)
{
int count=0;
for(count = 0; count < K; count++)
{
printf("row=%2d : %2d %2d\n",count+1,(lista->i)[count],(lista->j)[count]);
}
}
int compare(const void *a, const void *b)
{
// compare the values of two case of array pointed by i of type int
return *(int*)a-*(int*)b;
}
void sort(struct element *list)
{
// we will sort the array pointed by i which contains K elements
// of type int and size sizeof(int) by using the compare function
qsort(list->i, K , sizeof(int), compare);
}
I realized that compiling it with gcc command from terminal gives correct output but using the codeblocks v13.12 which uses the same internal GNU GCC compiler gives wrong output !!
The output of gcc command: gcc -g -Wall main.c -o exec
gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1)
--------- i --- j ---------
row= 1 : 8 8
row= 2 : 29 29
row= 3 : 9 9
row= 4 : 11 11
row= 5 : 20 20
row= 6 : 21 21
row= 7 : 4 4
row= 8 : 16 16
row= 9 : 9 9
row=10 : 2 2
---------------------------
row= 1 : 2 8
row= 2 : 4 29
row= 3 : 8 9
row= 4 : 9 11
row= 5 : 9 20
row= 6 : 11 21
row= 7 : 16 4
row= 8 : 20 16
row= 9 : 21 9
row=10 : 29 2
the output of codeblocks (please note the number of the starting row 3)
row= 3 : 20 20
row= 4 : 4 4
row= 5 : 13 13
row= 6 : 8 8
row= 7 : 4 4
row= 8 : 7 7
row= 9 : 21 21
row=10 : 12 12
---------------------------
row= 1 : 4 24
row= 2 : 4 22
row= 3 : 7 20
row= 4 : 8 4
row= 5 : 12 13
row= 6 : 13 8
row= 7 : 20 4
row= 8 : 21 7
row= 9 : 22 21
row=10 : 24 12
So I was wondering what can lead to such behavior ?
