fix cfn

sub/core/src/ffi.rs

@@ -15,10 +15,10 @@ pub macro cstr($str:expr) {
 /// | ```cfn!( (usize) -> usize )``` | ``` extern "C" fn(usize) -> usize``` |
 /// | ```cfn!( (usize) )``` | ``` extern "C" fn(usize)``` |
 /// | ```cfn!( (u32, usize, usize) -> u32 )``` | ``` extern "C" fn(u32, usize, usize) -> u32``` |
-pub macro cfn($str:expr) {
+pub macro cfn {
     ( ($($t:ty),*)) => {
         extern "C" fn($( $t ),* )
-    };
+    },
     ( ($($t:ty),*) -> $r:ty) => {
         extern "C" fn($( $t ),* ) -> $r
     }