Allow use of usdt probes with stable rust

Cargo.toml

@@ -12,9 +12,12 @@ serde = "1"
 serde_json = "1"
 slog = "2"
 chrono = { version = "0.4", features = [ "serde" ] }
-usdt = "0.2"
+usdt = "0.3.2"
 
 [dev-dependencies]
 slog-async = "2"
 slog-term = "2"
 subprocess = "0.2"
+
+[build-dependencies]
+version_check = "0.9.4"

build.rs

@@ -0,0 +1,28 @@
+// Copyright 2022 Oxide Computer Company
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+use version_check;
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    if version_check::is_min_version("1.59").unwrap_or(false) {
+        println!("cargo:rustc-cfg=usdt_stable_asm");
+    }
+
+    // Once asm_sym is stablilized, add an additional check so that those
+    // building on macos can use the stable toolchain with any hassle.
+    //
+    // A matching rust-cfg option named `usdt_stable_asm_sym` seems appropriate.
+}

src/lib.rs

@@ -53,22 +53,22 @@
 //!
 //! This crate inherits a reliance on a nightly toolchain from the `usdt` crate.
 
-// Copyright 2021 Oxide Computer Company
-// 
+// Copyright 2022 Oxide Computer Company
+//
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
-// 
+//
 //     http://www.apache.org/licenses/LICENSE-2.0
-// 
+//
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#![feature(asm)]
-#![cfg_attr(target_os = "macos", feature(asm_sym))]
+#![cfg_attr(not(usdt_stable_asm), feature(asm))]
+#![cfg_attr(all(target_os = "macos", not(usdt_stable_asm_sym)), feature(asm_sym))]
 
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};

tests/test-slog-dtrace.rs

@@ -1,20 +1,21 @@
 //! Integration test for the `slog-dtrace` crate.
 
 // Copyright 2021 Oxide Computer Company
-// 
+//
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
-// 
+//
 //     http://www.apache.org/licenses/LICENSE-2.0
-// 
+//
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#![feature(asm)]
+#![cfg_attr(not(usdt_stable_asm), feature(asm))]
+#![cfg_attr(all(target_os = "macos", not(usdt_stable_asm_sym)), feature(asm_sym))]
 
 fn main() {}