Auto merge of #102732 - RalfJung:assert_unsafe_precondition2, r=bjorn3

nicer errors from assert_unsafe_precondition

This makes the errors shown by cargo-careful nicer, and since `panic_no_unwind` is `nounwind noreturn` it hopefully doesn't have bad codegen impact. Thanks to `@bjorn3` for the hint!

Would be nice if we could somehow supply our own (static) message to print, currently it always prints `panic in a function that cannot unwind`. But still, this is better than before.

1 files changed, 8 insertions, 4 deletions

diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index 80b067812ba..8187517ccfb 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -28,16 +28,20 @@ extern "Rust" {
     // The rustc fork of LLVM 14 and earlier also special-cases these function names to be able to optimize them
     // like `malloc`, `realloc`, and `free`, respectively.
     #[rustc_allocator]
-    #[rustc_allocator_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_nounwind)]
+    #[cfg_attr(bootstrap, rustc_allocator_nounwind)]
     fn __rust_alloc(size: usize, align: usize) -> *mut u8;
     #[rustc_deallocator]
-    #[rustc_allocator_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_nounwind)]
+    #[cfg_attr(bootstrap, rustc_allocator_nounwind)]
     fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
     #[rustc_reallocator]
-    #[rustc_allocator_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_nounwind)]
+    #[cfg_attr(bootstrap, rustc_allocator_nounwind)]
     fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
     #[rustc_allocator_zeroed]
-    #[rustc_allocator_nounwind]
+    #[cfg_attr(not(bootstrap), rustc_nounwind)]
+    #[cfg_attr(bootstrap, rustc_allocator_nounwind)]
     fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
 }