From 53d502264bc64f61c53b9c1740098c3a0bcb7549 Mon Sep 17 00:00:00 2001
From: "Cliff L. Biffle" <cliff@oxide.computer>
Date: Tue, 29 Apr 2025 12:11:24 -0700
Subject: [PATCH] Basic crate for accessing task names at build time.

This allows tasks to refer to other tasks by name, which we need _very
rarely,_ but has come up for fault reporting.
---
 Cargo.lock                |  7 +++++++
 sys/task-names/Cargo.toml | 17 +++++++++++++++++
 sys/task-names/build.rs   | 29 +++++++++++++++++++++++++++++
 sys/task-names/src/lib.rs | 17 +++++++++++++++++
 4 files changed, 70 insertions(+)
 create mode 100644 sys/task-names/Cargo.toml
 create mode 100644 sys/task-names/build.rs
 create mode 100644 sys/task-names/src/lib.rs

diff --git a/Cargo.lock b/Cargo.lock
index b0b45f055..7fa134c0b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3128,6 +3128,13 @@ dependencies = [
  "build-util",
 ]
 
+[[package]]
+name = "hubris-task-names"
+version = "0.1.0"
+dependencies = [
+ "build-util",
+]
+
 [[package]]
 name = "hubtools"
 version = "0.4.6"
diff --git a/sys/task-names/Cargo.toml b/sys/task-names/Cargo.toml
new file mode 100644
index 000000000..f7da40058
--- /dev/null
+++ b/sys/task-names/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "hubris-task-names"
+version = "0.1.0"
+edition = "2021"
+
+[build-dependencies]
+build-util = { path = "../../build/util" }
+
+[features]
+
+[lib]
+test = false
+doctest = false
+bench = false
+
+[lints]
+workspace = true
diff --git a/sys/task-names/build.rs b/sys/task-names/build.rs
new file mode 100644
index 000000000..0c0317993
--- /dev/null
+++ b/sys/task-names/build.rs
@@ -0,0 +1,29 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use std::fs::File;
+use std::io::Write;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let out = build_util::out_dir();
+
+    let task_env = build_util::env_var("HUBRIS_TASKS").unwrap_or_else(|_| {
+        panic!("can't build this crate outside of the build system.")
+    });
+
+    let task_names = task_env.split(',').collect::<Vec<_>>();
+    let count = task_names.len();
+
+    let mut task_file = File::create(out.join("tasks.rs")).unwrap();
+    writeln!(task_file, "pub static TASK_NAMES: [&str; {count}] = [").unwrap();
+    for name in &task_names {
+        writeln!(task_file, "    {name:?},").unwrap();
+    }
+    writeln!(task_file, "];").unwrap();
+
+    let longest = task_names.iter().map(|s| s.len()).max().unwrap_or(0);
+    writeln!(task_file, "pub const MAX_TASK_NAME: usize = {longest};").unwrap();
+
+    Ok(())
+}
diff --git a/sys/task-names/src/lib.rs b/sys/task-names/src/lib.rs
new file mode 100644
index 000000000..74188eded
--- /dev/null
+++ b/sys/task-names/src/lib.rs
@@ -0,0 +1,17 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! Allows compile-time retrieval of task names in the current image.
+//!
+//! The code is generated, but here's what you can expect:
+//!
+//! `TASK_NAMES` is a `static` array of `&str`.
+//!
+//! `MAX_TASK_NAME` is a `const` `usize` giving the number of bytes in the
+//! longest task name. This can be useful for sizing buffers.
+
+#![no_std]
+#![forbid(clippy::wildcard_imports)]
+
+include!(concat!(env!("OUT_DIR"), "/tasks.rs"));