Rollup merge of #102742 - bjorn3:cleanup_rust_start_panic, r=ChrisDenton

Remove unnecessary raw pointer in __rust_start_panic arg

It is no longer necessary as __rust_start_panic switched to the Rust abi.

Author: matthiaskrgr

library/panic_abort/src/android.rs

@@ -15,15 +15,15 @@ type SetAbortMessageType = unsafe extern "C" fn(*const libc::c_char) -> ();
 //
 // Weakly resolve the symbol for android_set_abort_message. This function is only available
 // for API >= 21.
-pub(crate) unsafe fn android_set_abort_message(payload: *mut &mut dyn BoxMeUp) {
+pub(crate) unsafe fn android_set_abort_message(payload: &mut dyn BoxMeUp) {
     let func_addr =
         libc::dlsym(libc::RTLD_DEFAULT, ANDROID_SET_ABORT_MESSAGE.as_ptr() as *const libc::c_char)
             as usize;
     if func_addr == 0 {
         return;
     }
 
-    let payload = (*payload).get();
+    let payload = payload.get();
     let msg = match payload.downcast_ref::<&'static str>() {
         Some(msg) => msg.as_bytes(),
         None => match payload.downcast_ref::<String>() {

library/panic_abort/src/lib.rs

@@ -29,7 +29,7 @@ pub unsafe extern "C" fn __rust_panic_cleanup(_: *mut u8) -> *mut (dyn Any + Sen
 
 // "Leak" the payload and shim to the relevant abort on the platform in question.
 #[rustc_std_internal_symbol]
-pub unsafe fn __rust_start_panic(_payload: *mut &mut dyn BoxMeUp) -> u32 {
+pub unsafe fn __rust_start_panic(_payload: &mut dyn BoxMeUp) -> u32 {
     // Android has the ability to attach a message as part of the abort.
     #[cfg(target_os = "android")]
     android::android_set_abort_message(_payload);

library/panic_unwind/src/lib.rs

@@ -99,8 +99,8 @@ pub unsafe extern "C" fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any
 // Entry point for raising an exception, just delegates to the platform-specific
 // implementation.
 #[rustc_std_internal_symbol]
-pub unsafe fn __rust_start_panic(payload: *mut &mut dyn BoxMeUp) -> u32 {
-    let payload = Box::from_raw((*payload).take_box());
+pub unsafe fn __rust_start_panic(payload: &mut dyn BoxMeUp) -> u32 {
+    let payload = Box::from_raw(payload.take_box());
 
     imp::panic(payload)
 }

library/std/src/panicking.rs

@@ -46,12 +46,10 @@ extern "C" {
     fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static);
 }
 
-#[allow(improper_ctypes)]
 extern "Rust" {
-    /// `payload` is passed through another layer of raw pointers as `&mut dyn Trait` is not
-    /// FFI-safe. `BoxMeUp` lazily performs allocation only when needed (this avoids allocations
-    /// when using the "abort" panic runtime).
-    fn __rust_start_panic(payload: *mut &mut dyn BoxMeUp) -> u32;
+    /// `BoxMeUp` lazily performs allocation only when needed (this avoids
+    /// allocations when using the "abort" panic runtime).
+    fn __rust_start_panic(payload: &mut dyn BoxMeUp) -> u32;
 }
 
 /// This function is called by the panic runtime if FFI code catches a Rust
@@ -738,10 +736,7 @@ pub fn rust_panic_without_hook(payload: Box<dyn Any + Send>) -> ! {
 /// yer breakpoints.
 #[inline(never)]
 #[cfg_attr(not(test), rustc_std_internal_symbol)]
-fn rust_panic(mut msg: &mut dyn BoxMeUp) -> ! {
-    let code = unsafe {
-        let obj = &mut msg as *mut &mut dyn BoxMeUp;
-        __rust_start_panic(obj)
-    };
+fn rust_panic(msg: &mut dyn BoxMeUp) -> ! {
+    let code = unsafe { __rust_start_panic(msg) };
     rtabort!("failed to initiate panic, error {code}")
 }