segmentation fault...please help

[liaa]

the following problem sorts all sequences of k elements in a descending order...the algorithms are correct, as i tested them on a static allocation program...
i am having trouble with pointers and parameters transmition...

#include<stdio.h>
#include<stdlib.h>

void sort(int*v,int m,int k)
{
	int ok=0;
	int last =m+k-1, aux, i;
	while(!ok) {
		ok=1;
		for(i=m; i<last; i++)
			if(v[i]<v[i+1]) { aux=v[i];
					     v[i]=v[i+1];
					     v[i+1]=aux;
					     ok=0;
					}
		last-=1;
	}
}

void reading(int*v,int*n)
{
	int i;
	printf("n= ");
	scanf("%d",n);
	v=(int*)malloc(*n*sizeof(int));
	if(v==NULL)
	printf("allocation error!");
	for(i=0;i<*n;i++) {
		printf("v[%d]= ",i);
		scanf("%d",&v[i]);
	}
}

void printing(int*v,int n)
{
	int i;
	for(i=0;i<n;i++)
		printf("%d ",v[i]);
}


void sort_array(int*v,int n,int k)
{
	int j=0;
	while(j<n-k)
	{
		sort(v,j,k);
		j+=k;
	}
	
}

int main()
{
	int n, k;
	int*v;
	printf("k= ");
	scanf("%d",&k);
	reading(v,&n);
	sort_array(v,n,k);
	printing(v,n);
	printf("\n");
	return 0;
}

i am compiling and executing under linux...

[MK27]

used gdb or some printf statements to locate the segfault.

[vart]

you need to pass v by pointer into reading function
currectly changes made inside reading function to this var are not visible outside the function

[MK27]

You should malloc v in main(), or use reading() to return a pointer, because re-assigning the variable there (v=) will not be valid outside reading() unless the new address is returned.

[liaa]

thanks, guys now my program runs correctly, only that after execution says :null pointer assignment i have done the allocation in function main

[vart]

thanks, guys now my program runs correctly, only that after execution says :null pointer assignment i have done the allocation in function main

show your last code

[liaa]

thanks, vart, i figured it out