Merge #363

363: scb: derive serde, Hash, PartialOrd for VectActive behind gates r=thalesfragoso a=tmplt

Exposes two new feature gates for VectActive serde::{Serialize,
Deserialize} (via "serde") and Hash, PartialOrd (via "std-map") for use
on host-side ITM tracing programs. While the struct itself is not
received directly over ITM, its use greatly simplifies the
implementation by allowing VectActive as keys in map collections and
file/socket {,de}serialization to forward the structure elsewhere. These
features are not enabled by default.

Before this patch, serde functionality could be realized via [0], but
this does not propagate down a dependency chain (i.e. if realized for
crate B, which crate A depends on, serde functionality is not exposed in
crate A unless VectActive is wrapped in a type from crate B). I am not
aware of any method to realize PartialOrd, Hash derivation for a
downstream crate.

[0] https://serde.rs/remote-derive.html

Co-authored-by: Viktor Sonesten <v@tmplt.dev>

2 files changed, 26 insertions, 3 deletions

diff --git a/xtask/src/lib.rs b/xtask/src/lib.rs
index a7b85e7..c3d8356 100644
--- a/xtask/src/lib.rs
+++ b/xtask/src/lib.rs
@@ -208,3 +208,24 @@ pub fn check_blobs() {
 
     println!("Blobs identical.");
 }
+
+// Check that serde and PartialOrd works with VectActive
+pub fn check_host_side() {
+    use cortex_m::peripheral::scb::VectActive;
+
+    // check serde
+    {
+        let v = VectActive::from(22).unwrap();
+        let json = serde_json::to_string(&v).expect("Failed to serialize VectActive");
+        let deser_v: VectActive =
+            serde_json::from_str(&json).expect("Failed to deserialize VectActive");
+        assert_eq!(deser_v, v);
+    }
+
+    // check PartialOrd
+    {
+        let a = VectActive::from(19).unwrap();
+        let b = VectActive::from(20).unwrap();
+        assert_eq!(a < b, true);
+    }
+}
diff --git a/xtask/src/main.rs b/xtask/src/main.rs
index ec55bf8..3e4b394 100644
--- a/xtask/src/main.rs
+++ b/xtask/src/main.rs
@@ -1,17 +1,19 @@
 use std::{env, process};
-use xtask::{assemble_blobs, check_blobs};
+use xtask::{assemble_blobs, check_blobs, check_host_side};
 
 fn main() {
     let subcommand = env::args().skip(1).next();
     match subcommand.as_ref().map(|s| &**s) {
         Some("assemble") => assemble_blobs(),
         Some("check-blobs") => check_blobs(),
+        Some("check-host-side") => check_host_side(),
         _ => {
             eprintln!("usage: cargo xtask <subcommand>");
             eprintln!();
             eprintln!("subcommands:");
-            eprintln!("    assemble     Reassemble the pre-built artifacts");
-            eprintln!("    check-blobs  Check that the pre-built artifacts are up-to-date and reproducible");
+            eprintln!("    assemble         Reassemble the pre-built artifacts");
+            eprintln!("    check-blobs      Check that the pre-built artifacts are up-to-date and reproducible");
+            eprintln!("    check-host-side  Build the crate in a non-Cortex-M host application and check host side usage of certain types");
             process::exit(1);
         }
     }