Add an impl Format for PanicInfo

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - [#845]: `decoder`: fix println!() records being printed with formatting
 - [#843]: `defmt`: Sort IDs of log msgs by severity to allow runtime filtering by severity
 - [#822]: `CI`: Run `cargo semver-checks` on every PR
+- [#856]: `defmt`: Add a `Format` impl for `PanicInfo` and related types.
 
 [#859]: https://github.com/knurling-rs/defmt/pull/859
 [#858]: https://github.com/knurling-rs/defmt/pull/858
@@ -28,6 +29,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 [#845]: https://github.com/knurling-rs/defmt/pull/845
 [#843]: https://github.com/knurling-rs/defmt/pull/843
 [#822]: https://github.com/knurling-rs/defmt/pull/822
+[#856]: https://github.com/knurling-rs/defmt/pull/856
 
 ## [v0.3.8] - 2024-05-17
 

defmt/src/impls/core_/mod.rs

@@ -12,6 +12,7 @@ mod cell;
 mod net;
 mod num;
 mod ops;
+mod panic;
 mod ptr;
 mod slice;
 

defmt/src/impls/core_/panic.rs

@@ -0,0 +1,27 @@
+use core::panic;
+
+use super::*;
+
+impl<'a> Format for panic::PanicInfo<'a> {
+    fn format(&self, f: Formatter) {
+        if let Some(location) = self.location() {
+            crate::write!(f, "panicked at {}", location);
+        } else {
+            crate::write!(f, "panicked");
+        }
+        // TODO: consider supporting self.message() once stabilized, or add a crate feature for
+        // conditional support
+    }
+}
+
+impl<'a> Format for panic::Location<'a> {
+    fn format(&self, f: Formatter) {
+        crate::write!(
+            f,
+            "{=str}:{=u32}:{=u32}",
+            self.file(),
+            self.line(),
+            self.column()
+        );
+    }
+}

firmware/qemu/src/bin/panic_info.out

@@ -0,0 +1 @@
+INFO PanicInfo: panicked at qemu/src/bin/panic_info.rs:14:5

firmware/qemu/src/bin/panic_info.rs

@@ -0,0 +1,23 @@
+#![no_std]
+#![no_main]
+
+use core::panic;
+use cortex_m_semihosting::debug;
+
+use defmt_semihosting as _; // global logger
+
+#[cortex_m_rt::entry]
+fn main() -> ! {
+    // Note: this test is a bit brittle in that the line/column number of the following panic is
+    // included in the test snapshot.  Hence, be mindful to update the snapshot if you want to
+    // add any additional code to this file above the following line!
+    panic!("aaah!")
+}
+
+#[panic_handler]
+fn panic(panic_info: &panic::PanicInfo) -> ! {
+    defmt::info!("PanicInfo: {=?}", panic_info);
+    loop {
+        debug::exit(debug::EXIT_SUCCESS)
+    }
+}

xtask/src/snapshot.rs

@@ -26,6 +26,7 @@ pub(crate) fn all_snapshot_tests() -> Vec<&'static str> {
         "hints_inner",
         "dbg",
         "net",
+        "panic_info",
     ];
     const NIGHTLY_SNAPSHOT_TESTS: &[&str] = &["alloc"];