foo.cpp:28:18: error: declaration of 'step' as multidimensional array must have bounds for all dimensions except the first
 const int step[][] = {{1,0},{-1,0},{0,1},{0,-1}};
                  ^
foo.cpp:38:10: error: 'ey' has not been declared
  int ex ,ey;
          ^
foo.cpp:38:12: error: expected ')' before ';' token
  int ex ,ey;
            ^
foo.cpp:37:5: warning: second argument of 'int main(int, int)' should be 'char **' [-Wmain]
 int main(
     ^
foo.cpp:15:16: error: expected unqualified-id before 'for'
 #define f(x,y) for(register int x = 1; x <= y; x ++)
                ^
foo.cpp:40:2: note: in expansion of macro 'f'
  f(i,n) f(j,m) {
  ^
foo.cpp:40:4: error: 'i' does not name a type
  f(i,n) f(j,m) {
    ^
foo.cpp:15:40: note: in definition of macro 'f'
 #define f(x,y) for(register int x = 1; x <= y; x ++)
                                        ^
foo.cpp:40:4: error: 'i' does not name a type
  f(i,n) f(j,m) {
    ^
foo.cpp:15:48: note: in definition of macro 'f'
 #define f(x,y) for(register int x = 1; x <= y; x ++)
                                                ^
foo.cpp:40:11: error: 'j' does not name a type
  f(i,n) f(j,m) {
           ^
foo.cpp:15:40: note: in definition of macro 'f'
 #define f(x,y) for(register int x = 1; x <= y; x ++)
                                        ^
foo.cpp:40:11: error: 'j' does not name a type
  f(i,n) f(j,m) {
           ^
foo.cpp:15:48: note: in definition of macro 'f'
 #define f(x,y) for(register int x = 1; x <= y; x ++)
                                                ^
foo.cpp:49:2: error: expected unqualified-id before 'while'
  while (s != e ){
  ^