/in/foo.c: In function 'main':
/in/foo.c:2:11: error: expected expression before '=' token
 #define N = 1000000000
           ^
/in/foo.c:5:11: note: in expansion of macro 'N'
     int a[N];
           ^
/in/foo.c:2:11: error: expected expression before '=' token
 #define N = 1000000000
           ^
/in/foo.c:6:8: note: in expansion of macro 'N'
  int b[N];
        ^
/in/foo.c:10:10: error: 'o' undeclared (first use in this function)
  for(j = o;j<6;j++)
          ^
/in/foo.c:10:10: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:12:19: error: expected ']' before '}' token
   b[j] = a[(j+1)%6};
                   ^
/in/foo.c:12:19: error: expected ';' before '}' token
/in/foo.c:6:6: warning: unused variable 'b' [-Wunused-variable]
  int b[N];
      ^
/in/foo.c:5:9: warning: unused variable 'a' [-Wunused-variable]
     int a[N];
         ^
/in/foo.c: At top level:
/in/foo.c:14:5: error: expected identifier or '(' before 'for'
     for(j=0;j<6;j++)
     ^~~
/in/foo.c:14:14: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
     for(j=0;j<6;j++)
              ^
/in/foo.c:14:18: error: expected '=', ',', ';', 'asm' or '__attribute__' before '++' token
     for(j=0;j<6;j++)
                  ^~
/in/foo.c:16:12: error: expected declaration specifiers or '...' before string constant
     printf("\n");
            ^~~~
/in/foo.c:17:5: error: expected identifier or '(' before 'for'
     for(j=0;j<6;j++)
     ^~~
/in/foo.c:17:14: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
     for(j=0;j<6;j++)
              ^
/in/foo.c:17:18: error: expected '=', ',', ';', 'asm' or '__attribute__' before '++' token
     for(j=0;j<6;j++)
                  ^~
/in/foo.c:19:5: error: expected identifier or '(' before 'return'
     return 0;
     ^~~~~~
/in/foo.c:20:1: error: expected identifier or '(' before '}' token
 }
 ^