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Better detection of features necessary for USDT probes #561

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Merged
bnaecker merged 1 commit into from
Jan 11, 2023
Merged

Better detection of features necessary for USDT probes #561

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16 changes: 9 additions & 7 deletions dropshot/build.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Copyright 2022 Oxide Computer Company
// Copyright 2023 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.
Expand All @@ -16,12 +16,14 @@
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");
if !version_check::is_min_version("1.59").unwrap_or(false) {
println!("cargo:rustc-cfg=usdt_need_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.
#[cfg(target_os = "macos")]
if version_check::supports_feature("asm_sym").unwrap_or(false)
&& !version_check::is_min_version("1.67").unwrap_or(false)
{
println!("cargo:rustc-cfg=usdt_need_asm_sym");
}
}
21 changes: 9 additions & 12 deletions dropshot/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -505,11 +505,12 @@
//! See the [`RequestInfo`] and [`ResponseInfo`] types for a complete listing
//! of what's available.
//!
//! These probes are implemented via the [`usdt`] crate. They require a nightly
//! toolchain if built on MacOS (which requires the unstable `asm_sym` feature).
//! Otherwise a stable compiler >= v1.59 is required in order to present the
//! necessary features. Given these constraints, usdt functionality is behind
//! the feature flag `"usdt-probes"`.
//! These probes are implemented via the [`usdt`] crate. They may require a
//! nightly toolchain if built on macOS prior to Rust version 1.66. Otherwise a
//! stable compiler >= v1.59 is required in order to present the necessary
//! features. Given these constraints, USDT functionality is behind the feature
//! flag `"usdt-probes"`, which may become a default feature of this crate in
//! future releases.
//!
//! > *Important:* The probes are internally registered with the DTrace kernel
//! module, making them visible via `dtrace(1M)`. This is done when an `HttpServer`
Expand Down Expand Up @@ -540,15 +541,11 @@
// Clippy's style advice is definitely valuable, but not worth the trouble for
// automated enforcement.
#![allow(clippy::style)]
// The `usdt` crate requires nightly, enabled if our consumer is enabling
// The `usdt` crate may requires nightly, enabled if our consumer is enabling
// DTrace probes.
#![cfg_attr(all(feature = "usdt-probes", not(usdt_stable_asm)), feature(asm))]
#![cfg_attr(all(feature = "usdt-probes", usdt_need_asm), feature(asm))]
#![cfg_attr(
all(
feature = "usdt-probes",
target_os = "macos",
not(usdt_stable_asm_sym)
),
all(feature = "usdt-probes", target_os = "macos", usdt_need_asm_sym),
feature(asm_sym)
)]

Expand Down