feat(codspeed): collect Rust toolchain environment at build time

Capture rustc and cargo version information during compilation via
build.rs and register it through the instrument-hooks environment API
at runtime. This enables tracking which toolchain was used to compile
benchmarks.

- Update instrument-hooks submodule to get set_environment/write_environment API
- Regenerate FFI bindings for new environment functions
- Add set_environment/write_environment wrappers to InstrumentHooks
- Collect rustc (version, host, release, LLVM version) and cargo version
  at build time via env vars, register them during InstrumentHooks init
- Always initialize InstrumentHooks (even in Valgrind mode) for env collection

Generated with AI Agent (Claude Code)

Author: GuillaumeLagrange

crates/codspeed/build.rs

@@ -5,6 +5,9 @@ fn main() {
     println!("cargo:rerun-if-changed=instrument-hooks/includes/core.h");
     println!("cargo:rerun-if-changed=build.rs");
 
+    collect_rustc_info();
+    collect_cargo_info();
+
     let mut build = cc::Build::new();
     build
         .flag("-std=c11")
@@ -44,3 +47,54 @@ fn main() {
         }
     }
 }
+
+/// Collect rustc toolchain info at build time and expose as env vars.
+/// These env var names must be kept in sync with `src/instrument_hooks/mod.rs`.
+fn collect_rustc_info() {
+    let Ok(output) = std::process::Command::new("rustc")
+        .args(["--version", "--verbose"])
+        .output()
+    else {
+        return;
+    };
+    if !output.status.success() {
+        return;
+    }
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    for line in stdout.lines() {
+        if let Some(rest) = line.strip_prefix("rustc ") {
+            println!("cargo:rustc-env=CODSPEED_RUSTC_VERSION={rest}");
+        } else if let Some((key, value)) = line.split_once(':') {
+            let key = key.trim();
+            let value = value.trim();
+            let env_key = match key {
+                "release" => Some("CODSPEED_RUSTC_RELEASE"),
+                "LLVM version" => Some("CODSPEED_RUSTC_LLVM_VERSION"),
+                _ => None,
+            };
+            if let Some(env_key) = env_key {
+                println!("cargo:rustc-env={env_key}={value}");
+            }
+        }
+    }
+}
+
+/// Collect cargo version at build time and expose as an env var.
+/// This env var name must be kept in sync with `src/instrument_hooks/mod.rs`.
+fn collect_cargo_info() {
+    let Ok(output) = std::process::Command::new("cargo")
+        .arg("--version")
+        .output()
+    else {
+        return;
+    };
+    if !output.status.success() {
+        return;
+    }
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    if let Some(rest) = stdout.trim().strip_prefix("cargo ") {
+        println!("cargo:rustc-env=CODSPEED_CARGO_VERSION={rest}");
+    }
+}

crates/codspeed/instrument-hooks

@@ -36,19 +36,20 @@ impl CodSpeed {
     pub fn new() -> Self {
         use crate::instrument_hooks::InstrumentHooks;
         let instrumentation_status = {
-            // We completely bypass InstrumentHooks if we detect Valgrind via inline assembly
+            // Always initialize InstrumentHooks for environment collection,
+            // even when using Valgrind for the actual measurements.
+            let hooks_instance = InstrumentHooks::instance();
+
+            // We bypass InstrumentHooks if we detect Valgrind via inline assembly
             // Until we can reliably get rid of the inline assembly without causing breaking
             // changes in CPU simulation measurements by switching to InstrumentHooks only, we need
             // to keep this separation.
             if measurement::is_instrumented() {
                 InstrumentationStatus::Valgrind
+            } else if hooks_instance.is_instrumented() {
+                InstrumentationStatus::InstrumentHooks(hooks_instance)
             } else {
-                let hooks_instance = InstrumentHooks::instance();
-                if hooks_instance.is_instrumented() {
-                    InstrumentationStatus::InstrumentHooks(hooks_instance)
-                } else {
-                    InstrumentationStatus::NotInstrumented
-                }
+                InstrumentationStatus::NotInstrumented
             }
         };
 

crates/codspeed/src/codspeed.rs

@@ -58,3 +58,14 @@ pub type instrument_hooks_feature_t = ::std::os::raw::c_uint;
 extern "C" {
     pub fn instrument_hooks_set_feature(feature: instrument_hooks_feature_t, enabled: bool);
 }
+extern "C" {
+    pub fn instrument_hooks_set_environment(
+        arg1: *mut InstrumentHooks,
+        section_name: *const ::std::os::raw::c_char,
+        key: *const ::std::os::raw::c_char,
+        value: *const ::std::os::raw::c_char,
+    ) -> u8;
+}
+extern "C" {
+    pub fn instrument_hooks_write_environment(arg1: *mut InstrumentHooks, pid: u32) -> u8;
+}

crates/codspeed/src/instrument_hooks/bindings.rs

@@ -35,10 +35,36 @@ mod linux_impl {
                 instance
                     .set_integration("codspeed-rust", env!("CARGO_PKG_VERSION"))
                     .expect("Failed to set integration");
+                instance.register_toolchain_environment();
                 instance
             })
         }
 
+        /// Registers Rust toolchain information (captured at build time) via the
+        /// environment API.
+        ///
+        /// The env var names here must be kept in sync with `build.rs`.
+        fn register_toolchain_environment(&self) {
+            const SECTION: &str = "rust";
+
+            if let Some(v) = option_env!("CODSPEED_RUSTC_VERSION") {
+                let _ = self.set_environment(SECTION, "rustc", v);
+            }
+            if let Some(v) = option_env!("CODSPEED_RUSTC_RELEASE") {
+                let _ = self.set_environment(SECTION, "release", v);
+            }
+            if let Some(v) = option_env!("CODSPEED_RUSTC_LLVM_VERSION") {
+                let _ = self.set_environment(SECTION, "LLVM version", v);
+            }
+            if let Some(v) = option_env!("CODSPEED_CARGO_VERSION") {
+                let _ = self.set_environment(SECTION, "cargo", v);
+            }
+
+            if let Err(e) = self.write_environment() {
+                eprintln!("Warning: failed to write environment info: {e}");
+            }
+        }
+
         #[inline(always)]
         pub fn is_instrumented(&self) -> bool {
             unsafe { ffi::instrument_hooks_is_instrumented(self.0) }
@@ -131,6 +157,40 @@ mod linux_impl {
             }
         }
 
+        pub fn set_environment(
+            &self,
+            section_name: &str,
+            key: &str,
+            value: &str,
+        ) -> Result<(), u8> {
+            let c_section = CString::new(section_name).map_err(|_| 1u8)?;
+            let c_key = CString::new(key).map_err(|_| 1u8)?;
+            let c_value = CString::new(value).map_err(|_| 1u8)?;
+            let result = unsafe {
+                ffi::instrument_hooks_set_environment(
+                    self.0,
+                    c_section.as_ptr(),
+                    c_key.as_ptr(),
+                    c_value.as_ptr(),
+                )
+            };
+            if result == 0 {
+                Ok(())
+            } else {
+                Err(result)
+            }
+        }
+
+        pub fn write_environment(&self) -> Result<(), u8> {
+            let pid = std::process::id();
+            let result = unsafe { ffi::instrument_hooks_write_environment(self.0, pid) };
+            if result == 0 {
+                Ok(())
+            } else {
+                Err(result)
+            }
+        }
+
         pub fn disable_callgrind_markers() {
             unsafe {
                 ffi::instrument_hooks_set_feature(
@@ -187,6 +247,19 @@ mod other_impl {
             0
         }
 
+        pub fn set_environment(
+            &self,
+            _section_name: &str,
+            _key: &str,
+            _value: &str,
+        ) -> Result<(), u8> {
+            Ok(())
+        }
+
+        pub fn write_environment(&self) -> Result<(), u8> {
+            Ok(())
+        }
+
         pub fn disable_callgrind_markers() {}
     }
 }