sync implementation

src/header/unistd/mod.rs

@@ -647,7 +647,7 @@ pub unsafe extern "C" fn symlink(path1: *const c_char, path2: *const c_char) ->
 
 // #[no_mangle]
 pub extern "C" fn sync() {
-    unimplemented!();
+    Sys::sync();
 }
 
 #[no_mangle]

src/platform/linux/mod.rs

@@ -476,6 +476,10 @@ impl Pal for Sys {
         e(unsafe { syscall!(SYMLINKAT, path1.as_ptr(), AT_FDCWD, path2.as_ptr()) }) as c_int
     }
 
+    fn sync() -> c_int {
+        e(unsafe { syscall!(SYNC) }) as c_int
+    }
+
     fn umask(mask: mode_t) -> mode_t {
         unsafe { syscall!(UMASK, mask) as mode_t }
     }

src/platform/pal/mod.rs

@@ -175,6 +175,8 @@ pub trait Pal {
 
     fn symlink(path1: &CStr, path2: &CStr) -> c_int;
 
+    fn sync() -> c_int;
+
     fn umask(mask: mode_t) -> mode_t;
 
     fn uname(utsname: *mut utsname) -> c_int;

src/platform/redox/mod.rs

@@ -827,6 +827,10 @@ impl Pal for Sys {
         0
     }
 
+    fn sync() -> c_int {
+        0
+    }
+
     fn umask(mask: mode_t) -> mode_t {
         e(syscall::umask(mask as usize)) as mode_t
     }