lockf implementation proposal

src/platform/linux/mod.rs

@@ -210,7 +210,7 @@ impl Pal for Sys {
         res
     }
 
-    fn fcntl(fildes: c_int, cmd: c_int, arg: c_int) -> c_int {
+    fn fcntl(fildes: c_int, cmd: c_int, arg: c_ulonglong) -> c_int {
         e(unsafe { syscall!(FCNTL, fildes, cmd, arg) }) as c_int
     }
 

src/platform/pal/mod.rs

@@ -67,7 +67,7 @@ pub trait Pal {
 
     fn fstatvfs(fildes: c_int, buf: *mut statvfs) -> c_int;
 
-    fn fcntl(fildes: c_int, cmd: c_int, arg: c_int) -> c_int;
+    fn fcntl(fildes: c_int, cmd: c_int, arg: c_ulonglong) -> c_int;
 
     fn fork() -> pid_t;
 

src/platform/redox/mod.rs

@@ -259,7 +259,7 @@ impl Pal for Sys {
         e(syscall::fchown(fd as usize, owner as u32, group as u32)) as c_int
     }
 
-    fn fcntl(fd: c_int, cmd: c_int, args: c_int) -> c_int {
+    fn fcntl(fd: c_int, cmd: c_int, args: c_ulonglong) -> c_int {
         e(syscall::fcntl(fd as usize, cmd as usize, args as usize)) as c_int
     }