Merge #421

421: Allow #[naked] attribute on interrupt handlers and pre_init r=thalesfragoso a=adamgreig

Might be useful for `pre_init` especially, now that constrained naked functions are hopefully [on the road to being stable](rust-lang/rust#90957).

`pre_init` and `entry` are called from our `asm.S` via `bl __pre_init` and `bl main`, exception and interrupt handlers are called directly by the CPU; in either case there's no issue with calling a naked function.

Inspired by https://twitter.com/the6p4c/status/1489266955232034817

Co-authored-by: Adam Greig <[email protected]>

Author: bors[bot]

cortex-m-rt/macros/src/lib.rs

@@ -612,6 +612,7 @@ fn check_attr_whitelist(attrs: &[Attribute], caller: WhiteListCaller) -> Result<
         "deny",
         "forbid",
         "cold",
+        "naked",
     ];
 
     'o: for attr in attrs {