Remove unnecessary transmute

Author: benfogle

libbpf-rs/src/print.rs

@@ -35,19 +35,12 @@ fn default_callback(lvl: PrintLevel, msg: &str) {
     let _ = io::stderr().write(msg.as_bytes());
 }
 
-// not allowed to use function pointers in const functions, so it needs to be a macro
-macro_rules! to_ptr {
-    ($x:expr) => {
-        unsafe { std::mem::transmute::<PrintCallback, *mut ()>($x) }
-    };
-}
-
 fn from_ptr(ptr: *mut ()) -> PrintCallback {
     unsafe { std::mem::transmute::<*mut (), PrintCallback>(ptr) }
 }
 
 // There is no AtomicFnPtr. This is a workaround.
-static PRINT_CB: AtomicPtr<()> = AtomicPtr::new(to_ptr!(default_callback));
+static PRINT_CB: AtomicPtr<()> = AtomicPtr::new(default_callback as *mut ());
 
 /// libbpf's default cb uses vfprintf's return code...which is ignored everywhere. Mimic that for
 /// completeness
@@ -81,7 +74,7 @@ extern "C" fn outer_print_cb(
 ///
 /// This overrides (and is overridden by) [`ObjectBuilder::debug`]
 pub fn set_print(func: PrintCallback) -> PrintCallback {
-    let cb = to_ptr!(func);
+    let cb = func as *mut ();
     let prev = PRINT_CB.swap(cb, Ordering::Relaxed);
     unsafe { libbpf_sys::libbpf_set_print(Some(outer_print_cb)) };
     from_ptr(prev)