sort.c(13) : error C2371: 'shellSort' : redefinition; different basic types

[AlexC]

program in C, shell sort.

i've got this error : sort.c(13) : error C2371: 'shellSort' : redefinition; different basic types

#include <stdio.h>

int a[6] = {5, 9 , 2, 8, 7, 1};
int main(){
	int m;
	m = 0;
	shellSort(a, 6);
	for(m = 0; m<20; m++)
		printf("\n%d", a[m]);

	return 0;
}
void shellSort( int a[],int N){
	int i, j, inc;
	int tmp;
	for(inc = N/2; inc>0; inc /= 2)
		for(i = inc; i < N; i ++)
		{
			tmp = a[i];
			for(j = i; j>= inc; j -= inc)
				if(tmp <a[j-inc])
					a[j] = a[j - inc];
				else 
					break;
			a[j] = tmp;
		}

}

[Banfa]

Is that the only message you get nothing on line 7?

You called shellSort at line 7, it wasn't prototyped so the C compiler automatically assigned as a prototype returning int it declared it as

int shellSort();

Then at line 15 you define it as

void shellSort( int a[],int N)

And you get an error because you have defined it as returning void but the compiler declared it as returning int.

Predeclare you function at line 2 to avoid this.

[AlexC]

Thanks, I need to study so much. I didn't know that.
this is fixed up code

#include <stdio.h>

int a[6] = {5, 9 , 2, 8, 7, 1};
int main(){
	int m;
	m = 0;
	printf("Unsorted list:");
	for(m = 0; m<6; m++)
		printf("\n%d", a[m]);
	shellSort(a, 6);
	printf("\nShell Sorted: ");
	for(m = 0; m<6; m++)
		printf("\n%d", a[m]);

	return 0;
}
int shellSort( int a[],int N){
	int i, j, inc;
	int tmp;
	for(inc = N/2; inc>0; inc /= 2)
		for(i = inc; i < N; i ++)
		{
			tmp = a[i];
			for(j = i; j>= inc; j -= inc)
				if(tmp <a[j-inc])
					a[j] = a[j - inc];
				else 
					break;
			a[j] = tmp;
		}
return 0;
}