bump the cortex-m-rt to v0.4.0

examples/panic.rs

@@ -1,53 +1,26 @@
-//! Defining the panic handler
+//! Changing the panic handler
 //!
-//! The panic handler can be defined through the `panic_fmt` [language item][1].
-//! Make sure that the "abort-on-panic" feature of the cortex-m-rt crate is
-//! disabled to avoid redefining the language item.
+//! The easiest way to change the panic handler is to use a different [panic implementation
+//! crate][0].
 //!
-//! [1]: https://doc.rust-lang.org/unstable-book/language-features/lang-items.html
+//! [0]: https://crates.io/keywords/panic-impl
 //!
 //! ---
 
-#![feature(core_intrinsics)]
-#![feature(lang_items)]
 #![feature(used)]
 #![no_std]
 
 extern crate cortex_m;
 extern crate cortex_m_rt;
-extern crate cortex_m_semihosting;
-
-use core::fmt::Write;
-use core::intrinsics;
+// extern crate panic_abort;
+extern crate panic_semihosting; // reports panic messages to the host stderr using semihosting
 
 use cortex_m::asm;
-use cortex_m_semihosting::hio;
 
 fn main() {
     panic!("Oops");
 }
 
-#[lang = "panic_fmt"]
-#[no_mangle]
-pub unsafe extern "C" fn rust_begin_unwind(
-    args: core::fmt::Arguments,
-    file: &'static str,
-    line: u32,
-    col: u32,
-) -> ! {
-    if let Ok(mut stdout) = hio::hstdout() {
-        write!(stdout, "panicked at '")
-            .and_then(|_| {
-                stdout
-                    .write_fmt(args)
-                    .and_then(|_| writeln!(stdout, "', {}:{}:{}", file, line, col))
-            })
-            .ok();
-    }
-
-    intrinsics::abort()
-}
-
 // As we are not using interrupts, we just register a dummy catch all handler
 #[link_section = ".vector_table.interrupts"]
 #[used]