/in/foo.c: In function 'main':
/in/foo.c:14:23: warning: implicit declaration of function 'intersections' [-Wimplicit-function-declaration]
         printf("%d\n",intersections(a,b,c,d));
                       ^~~~~~~~~~~~~
/in/foo.c: In function 'intersections':
/in/foo.c:21:8: warning: implicit declaration of function 'direction' [-Wimplicit-function-declaration]
     d1=direction(c,d,a);
        ^~~~~~~~~
/in/foo.c:27:20: warning: implicit declaration of function 'onSegment' [-Wimplicit-function-declaration]
     else if(d1==0&&onSegment(c,d,a))
                    ^~~~~~~~~
/in/foo.c: In function 'onSegment':
/in/foo.c:63:12: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
     if(minx<=c.x<=maxx&&miny<=c.y<=maxy)
        ~~~~^~~~~
/in/foo.c:63:29: warning: comparisons like 'X<=Y<=Z' do not have their mathematical meaning [-Wparentheses]
     if(minx<=c.x<=maxx&&miny<=c.y<=maxy)
                         ~~~~^~~~~