opt-in panic_fmt implementation

that just calls intrinsics::abort

Author: japaric

cortex-m-rt/Cargo.toml

@@ -7,7 +7,7 @@ keywords = ["arm", "cortex-m", "runtime", "startup"]
 license = "MIT OR Apache-2.0"
 name = "cortex-m-rt"
 repository = "https://github.com/japaric/cortex-m-rt"
-version = "0.2.4"
+version = "0.3.0"
 
 [dependencies]
 r0 = "0.2.1"
@@ -22,3 +22,5 @@ default = ["exceptions", "linker-script"]
 exceptions = ["cortex-m"]
 # generic linker script
 linker-script = []
+# provides a panic_fmt implementation that calls the abort instruction (`udf 0xfe`)
+abort-on-panic = []

cortex-m-rt/src/lang_items.rs

@@ -1,28 +1,14 @@
 /// Default panic handler
+#[cfg(feature = "abort-on-panic")]
 #[lang = "panic_fmt"]
-#[linkage = "weak"]
 unsafe extern "C" fn panic_fmt(
-    _args: ::core::fmt::Arguments,
-    _file: &'static str,
-    _line: u32,
+    _: ::core::fmt::Arguments,
+    _: &'static str,
+    _: u32,
 ) -> ! {
     ::core::intrinsics::abort()
 }
 
-#[macro_export]
-macro_rules! panic_fmt {
-    ($f:expr) => {
-        #[export_name = "rust_begin_unwind"]
-        pub unsafe extern "C" fn _panic_fmt(
-            args: ::core::fmt::Arguments,
-            file: &'static str,
-            line: u32,
-        ) -> ! {
-            $f(args, file, line)
-        }
-    }
-}
-
 /// Lang item required to make the normal `main` work in applications
 // This is how the `start` lang item works:
 // When `rustc` compiles a binary crate, it creates a `main` function that looks

cortex-m-rt/src/lib.rs

@@ -145,11 +145,11 @@
 //!  8000404:       b084            sub     sp, #16
 //! ```
 
+#![cfg_attr(feature = "abort-on-panic", feature(core_intrinsics))]
 #![deny(missing_docs)]
 #![deny(warnings)]
 #![feature(asm)]
 #![feature(compiler_builtins_lib)]
-#![feature(core_intrinsics)]
 #![feature(lang_items)]
 #![feature(linkage)]
 #![feature(used)]
@@ -186,8 +186,8 @@ extern "C" {
 /// This is the entry point of all programs
 #[link_section = ".reset_handler"]
 unsafe extern "C" fn reset_handler() -> ! {
-    ::r0::zero_bss(&mut _sbss, &mut _ebss);
-    ::r0::init_data(&mut _sdata, &mut _edata, &_sidata);
+    r0::zero_bss(&mut _sbss, &mut _ebss);
+    r0::init_data(&mut _sdata, &mut _edata, &_sidata);
 
     // Neither `argc` or `argv` make sense in bare metal context so we just
     // stub them