Rollup merge of #130381 - workingjubilee:sometimes-code-really-is-self-descriptive, r=Noratrieb

library: Compute Rust exception class from its string repr
Noticed this awkwardness while scanning through the code. I think we can do better than that.

Author: matthiaskrgr

library/panic_unwind/src/gcc.rs

@@ -61,7 +61,7 @@ struct Exception {
 pubunsafefnpanic(data:Box<dynAny + Send>) -> u32{
 let exception = Box::new(Exception{
 _uwe: uw::_Unwind_Exception{
-exception_class:rust_exception_class(),
+exception_class:RUST_EXCEPTION_CLASS,
 exception_cleanup:Some(exception_cleanup),
 private:[core::ptr::null(); uw::unwinder_private_data_size],
 },
@@ -84,7 +84,7 @@ pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
 
 pubunsafefncleanup(ptr:*mutu8) -> Box<dynAny + Send>{
 let exception = ptr as*mut uw::_Unwind_Exception;
-if(*exception).exception_class != rust_exception_class(){
+if(*exception).exception_class != RUST_EXCEPTION_CLASS{
  uw::_Unwind_DeleteException(exception);
 super::__rust_foreign_exception();
 }
@@ -107,7 +107,4 @@ pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
 
 // Rust's exception class identifier. This is used by personality routines to
 // determine whether the exception was thrown by their own runtime.
-fnrust_exception_class() -> uw::_Unwind_Exception_Class{
-// M O Z \0 R U S T -- vendor, language
-0x4d4f5a_00_52555354
-}
+constRUST_EXCEPTION_CLASS: uw::_Unwind_Exception_Class = u64::from_be_bytes(*b"MOZ\0RUST");