Panicking

✅ Open the src/bin/panic.rs file and click the "Run" button.

This program attempts to index an array beyond its length and this results in a panic.

──────────────────────────────────────────────────────────────────────────────── ERROR panicked at 'index out of bounds: the len is 3 but the index is 3', src/bin/panic.rs:32:13 ──────────────────────────────────────────────────────────────────────────────── stack backtrace: 0: HardFaultTrampoline <exception entry> 1: lib::inline::__udf at ./asm/inline.rs:172:5 2: __udf at ./asm/lib.rs:49:17 3: cortex_m::asm::udf at /Users/name/.cargo/registry/src/github.com-1ecc6299db9ec823/cortex-m-0.7.3/src/asm.rs:43:5 4: rust_begin_unwind at /Users/name/.cargo/registry/src/github.com-1ecc6299db9ec823/panic-probe-0.3.0/src/lib.rs:72:9 5: core::panicking::panic_fmt at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:100:14 6: core::panicking::panic_bounds_check at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:76:5 7: panic::bar at src/bin/panic.rs:32:13 8: panic::foo at src/bin/panic.rs:25:5 9: panic::__cortex_m_rt_main at src/bin/panic.rs:15:5 10: main at src/bin/panic.rs:11:1 11: Reset (HOST) ERROR the program panicked

In no_std programs the behavior of panic is defined using the #[panic_handler] attribute. In the example, the panic handler is defined in the panic_log crate but we can also implement it manually:

✅ Comment out the use apps as _; import and add the following function to the example:

#![allow(unused)] fn main() { #[panic_handler] fn panic(info: &core::panic::PanicInfo) -> ! { defmt::error!("{}", defmt::Debug2Format(info)); asm::udf(); } }

Now run the program again. Try changing the format string of the panic! macro.