/in/foo.c:2:1: warning: data definition has no type or storage class
 Sum(int a[],int t1,int t2);
 ^~~
/in/foo.c:2:1: warning: type defaults to 'int' in declaration of 'Sum' [-Wimplicit-int]
/in/foo.c:24:1: warning: return type defaults to 'int' [-Wimplicit-int]
 Sum(int a[],int t1,int t2)
 ^~~