Auto merge of #80267 - 0urobor0s:ouro/61592, r=jyn514

[rust.git] / library / std / src / panicking.rs

diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs
index 8ba3feccb6bcc8f817efa43cd0b373124c27bcd8..6cd572cbe87c131b661d56d7483d62df2e2c551e 100644 (file)
--- a/library/std/src/panicking.rs
+++ b/library/std/src/panicking.rs
@@ -44,11 +44,11 @@
 extern "C" {
     fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static);
 
-    /// `payload` is actually a `*mut &mut dyn BoxMeUp` but that would cause FFI warnings.
-    /// It cannot be `Box<dyn BoxMeUp>` because the other end of this call does not depend
-    /// on liballoc, and thus cannot use `Box`.
+    /// `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).
     #[unwind(allowed)]
-    fn __rust_start_panic(payload: usize) -> u32;
+    fn __rust_start_panic(payload: *mut &mut dyn BoxMeUp) -> u32;
 }
 
 /// This function is called by the panic runtime if FFI code catches a Rust
@@ -637,7 +637,7 @@ fn get(&mut self) -> &(dyn Any + Send) {
 fn rust_panic(mut msg: &mut dyn BoxMeUp) -> ! {
     let code = unsafe {
         let obj = &mut msg as *mut &mut dyn BoxMeUp;
-        __rust_start_panic(obj as usize)
+        __rust_start_panic(obj)
     };
     rtabort!("failed to initiate panic, error {}", code)
 }