foo.c:14:13: error: variably modified 'RBTree' at file scope
 struct node RBTree[MAXN];
             ^
foo.c: In function 'RB_find':
foo.c:186:8: error: 'true' undeclared (first use in this function)
  while(true)
        ^
foo.c:186:8: note: each undeclared identifier is reported only once for each function it appears in
foo.c:201:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^