Use #[panic_implementation] attribute that was landed in the recent nightly

substrate/runtime-io/src/lib.rs

@@ -20,6 +20,7 @@
 #![cfg_attr(not(feature = "std"), feature(lang_items))]
 #![cfg_attr(not(feature = "std"), feature(core_intrinsics))]
 #![cfg_attr(not(feature = "std"), feature(alloc))]
+#![cfg_attr(not(feature = "std"), feature(panic_implementation))]
 
 #![cfg_attr(feature = "std", doc = "Substrate runtime standard library as compiled when linked with Rust's standard library.")]
 #![cfg_attr(not(feature = "std"), doc = "Substrate's runtime standard library as compiled without Rust's standard library.")]

substrate/runtime-io/without_std.rs

@@ -27,13 +27,15 @@ use rstd::intrinsics;
 use rstd::vec::Vec;
 pub use rstd::{mem, slice};
 
-#[lang = "panic_fmt"]
+#[panic_implementation]
 #[no_mangle]
-pub extern fn panic_fmt(_fmt: ::core::fmt::Arguments, _file: &'static str, _line: u32, _col: u32) {
+pub fn rust_begin_panic(info: &::core::panic::PanicInfo) -> ! {
 	unsafe {
-		ext_print_utf8(_file.as_ptr() as *const u8, _file.len() as u32);
-		ext_print_num(_line as u64);
-		ext_print_num(_col as u64);
+		if let Some(loc) = info.location() {
+			ext_print_utf8(loc.file().as_ptr() as *const u8, loc.file().len() as u32);
+			ext_print_num(loc.line() as u64);
+			ext_print_num(loc.column() as u64);
+		}
 		intrinsics::abort()
 	}
 }