Segmentation fault with multithreaded array - c

Question

I am trying to make multithread array sorting program in c. But when I run the program, I get an "segmentation fault" error.
Can someone help?
What should I change? First array should be 300 the other should be 500. We sort sequences separately first. After that merge 2 sorted sequences. I use "gcc -pthreads -0 soru1 soru1.c" and "./soru1" commands.
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <time.h>
#define size 800
int orginal_dizi[size], dizi1[300], dizi2[500], dizi3[size];
int sayi,a=1;
int boyutbul(int *the)
{
int number=-1;
while(the[++number]!='\0'){}
return number;
}
void*runner(void *param)
{
int temp,i,k;
int *bolum = param;
sayi = boyutbul(bolum);
printf("\n----------unsorted %d. array-----------\n\n",a);
for(i=0; i<sayi;i++)
printf("%d\n", bolum[i]);
for(i=0; i<sayi;i++)
{
for(k=0; k<(sayi-i-1);k++)
{
if(bolum[k]>bolum[k+1])
{
temp=bolum[k];
bolum[k]=bolum[k+1];
bolum[k+1]=temp;
}
}
}
printf("\n----------sorted %d. array-----------\n\n",a);
for(i=0; i<sayi;i++)
printf("%d\n", bolum[i]);
a++;
pthread_exit(0);
}
int main()
{
pthread_t tid1,tid2, tid3;
int i=0;
while(i<size)
{
int yenisayi=1+rand()%1500;
int aynimi=0, j=0;
while(j<i)
{
if(orginal_dizi[j]==yenisayi)
{
aynimi=1;
break;
}
j++;
}
if(aynimi)
continue;
orginal_dizi[i]=yenisayi;
i++;
}
for(i=0;i<size;i++)
{
if(i<(300))
{
dizi1[i]=orginal_dizi[i];
}
else
{
dizi2[i-(500)-1]= orginal_dizi[i];
}
}
pthread_create(&tid1,NULL,runner,(void *)dizi1);
pthread_join(tid1,NULL);
pthread_create(&tid2,NULL,runner,(void *)dizi2);
pthread_join(tid2,NULL);
for(i=0; i<size;i++)
{
if(i<300)
{
dizi3[i]=dizi1[i];
}
else
{
dizi3[i]=dizi2[i-500];
}
}
pthread_create(&tid3,NULL,runner,(void *)dizi3);
pthread_join(tid3,NULL);
FILE *fp;
if((fp=fopen("son.txt","w"))== NULL)
printf("Dosya acilamadi.");
for(i=0;i<size;i++)
{
fprintf(fp, "%d\n", dizi3[i]);
}
fclose(fp);
return 0;
}

Answer 1

There is no multithreading in this program: every thread is immediately joined; noting runs in parallel.
The real problem is in boyutbul, which tries to figure out the length of the array by looking for '\0'. The way you initialize the arrays, there is no guarantee that they would have the terminating 0 (in fact, they wouldn't have any zeroes), so the program is doomed to access them beyond the bounds. This is UB.