[C] Mergesort

[vfldj]

Ciao, devo scrivere una funzione mergesort in C. L'ho fatto ma non mi funziona. Il codice è:

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

void msort(int a[], int n) {
	int aux[] = copy(a, aux, n);
	msort2(a, 0, n - 1, aux);
}

void msort2(int a[], int fst, int lst, int b[]) {
	if(fst < lst) {
		int m = (fst + lst) / 2;
		msort2(b, fst, m, a);
		msort2(b, m + 1, lst, a);
		merge(b, fst, m, lst, a);
	}
}

int[] copy(int a[], int aux[], int n) {
	int i;
	for(i = 0; i < n; i++)
		aux[i] = a[i];
        return aux;
}

void merge(int a[], int fst, int mid, int lst, int c[]) {
	int i = fst;
	int j = mid + 1;
	int k = fst;
	while(i <= mid && j <= lst) {
		if(a[i] <= a[j])
			c[k++] = a[i++];
		else
			c[k++] = a[j++];
	}
	while(i <= mid)
		c[k++] = a[i++];
	while(j <= lst)
		c[k++] = a[j++];
}

File header:

void msort(int a[], int n);
void msort2(int a[], int fst, int lst, int b[]);
int[] copy(int a[], int aux[], int n);
void merge(int a[], int fst, int mid, int lst, int c[]);

Messaggio d'errore:

In file included from sorting.c:6:0:
sorting.h:8:4: error: expected identifier or ‘(’ before ‘[’ token
sorting.c: In function ‘msort’:
sorting.c:81:2: error: invalid initializer
sorting.c: At top level:
sorting.c:94:4: error: expected identifier or ‘(’ before ‘[’ token

Dove sbaglio? La funzione copy è giusta?

Grazie