feat(memtrack): support CODSPEED_MEMTRACK_BINARIES for static allocator discovery

Memtrack discovers allocators by scanning known build directories, but
exec CLI binaries may not live there. This causes memory profiling to
miss allocations when the binary has a statically linked allocator
(common in Rust).

Add CODSPEED_MEMTRACK_BINARIES env var (colon-separated paths) that
tells memtrack additional binaries to scan. The exec CLI auto-sets it
by resolving exec target binary paths before execution.

COD-2347

Author: not-matthias

Cargo.lock

@@ -72,6 +72,7 @@ tabled = { version = "0.20.0", features = ["ansi"] }
 shell-words = "1.1.0"
 rmp-serde = "1.3.0"
 uuid = { version = "1.21.0", features = ["v4"] }
+which = "8.0.2"
 
 [target.'cfg(target_os = "linux")'.dependencies]
 procfs = "0.17.0"

Cargo.toml

@@ -71,9 +71,45 @@ pub struct AllocatorLib {
 impl AllocatorLib {
     pub fn find_all() -> anyhow::Result<Vec<AllocatorLib>> {
         let mut allocators = static_linked::find_all()?;
+        allocators.extend(Self::find_from_env());
         allocators.extend(dynamic::find_all()?);
         Ok(allocators)
     }
+
+    /// Discover allocators from binaries listed in the `CODSPEED_MEMTRACK_BINARIES` env var.
+    ///
+    /// The variable is a colon-separated list of paths. Each path is checked for
+    /// a statically linked allocator via [`AllocatorLib::from_path_static`].
+    /// Invalid or missing paths are silently skipped (with a debug log).
+    fn find_from_env() -> Vec<AllocatorLib> {
+        let Ok(raw) = std::env::var("CODSPEED_MEMTRACK_BINARIES") else {
+            return vec![];
+        };
+
+        raw.split(':')
+            .filter(|p| !p.is_empty())
+            .filter_map(|p| {
+                let path = std::path::PathBuf::from(p);
+                match Self::from_path_static(&path) {
+                    Ok(alloc) => {
+                        log::debug!(
+                            "Found {} allocator in env-specified binary: {}",
+                            alloc.kind.name(),
+                            path.display()
+                        );
+                        Some(alloc)
+                    }
+                    Err(e) => {
+                        log::debug!(
+                            "Skipping env-specified binary {}: {e}",
+                            path.display()
+                        );
+                        None
+                    }
+                }
+            })
+            .collect()
+    }
 }
 
 /// Check if a file is an ELF binary by reading its magic bytes.

crates/memtrack/src/allocators/mod.rs

@@ -123,6 +123,41 @@ pub async fn execute_config(
     codspeed_config: &CodSpeedConfig,
     setup_cache_dir: Option<&Path>,
 ) -> Result<()> {
+    // Set CODSPEED_MEMTRACK_BINARIES so memtrack can discover statically linked
+    // allocators in exec target binaries (which may not live in known build dirs).
+    let memtrack_binaries: Vec<String> = config
+        .targets
+        .iter()
+        .filter_map(|t| match t {
+            executor::BenchmarkTarget::Exec { command, .. } => command.first().cloned(),
+            _ => None,
+        })
+        .filter_map(|bin| {
+            let result = match &config.working_directory {
+                Some(cwd) => which::which_in(&bin, std::env::var_os("PATH"), cwd),
+                None => which::which(&bin),
+            };
+            match result {
+                Ok(path) => Some(path.to_string_lossy().into_owned()),
+                Err(e) => {
+                    debug!("Could not resolve exec binary {bin:?}: {e}");
+                    None
+                }
+            }
+        })
+        .collect();
+
+    if !memtrack_binaries.is_empty() {
+        let mut all_paths = memtrack_binaries;
+        if let Ok(existing) = std::env::var("CODSPEED_MEMTRACK_BINARIES") {
+            if !existing.is_empty() {
+                all_paths.push(existing);
+            }
+        }
+        // SAFETY: The runner uses single-threaded tokio, so no concurrent env access.
+        unsafe { std::env::set_var("CODSPEED_MEMTRACK_BINARIES", all_paths.join(":")) };
+    }
+
     let orchestrator = executor::Orchestrator::new(config, codspeed_config, api_client).await?;
 
     if !orchestrator.is_local() {