feat(common): add current thread id API

libdd-common/Cargo.toml

@@ -47,7 +47,7 @@ const_format = "0.2.34"
 nix = { version = "0.29", features = ["process"] }
 [target.'cfg(windows)'.dependencies.windows-sys]
 version = "0.52"
-features = ["Win32_Foundation", "Win32_System_Performance"]
+features = ["Win32_Foundation", "Win32_System_Performance", "Win32_System_Threading"]
 
 [target.'cfg(unix)'.dependencies]
 rustls = { version = "0.23", default-features = false, optional = true, features = ["aws-lc-rs"] }

libdd-common/src/lib.rs

@@ -28,6 +28,7 @@ pub mod rate_limiter;
 pub mod tag;
 #[cfg(any(test, feature = "test-utils"))]
 pub mod test_utils;
+pub mod threading;
 pub mod timeout;
 pub mod unix_utils;
 pub mod worker;

libdd-common/src/threading.rs

@@ -0,0 +1,36 @@
+// Copyright 2026-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(target_os = "linux")]
+pub fn get_current_thread_id() -> i64 {
+    // SAFETY: syscall(SYS_gettid) has no preconditions for current thread.
+    unsafe { libc::syscall(libc::SYS_gettid) as i64 }
+}
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(target_os = "macos")]
+pub fn get_current_thread_id() -> i64 {
+    let mut tid: u64 = 0;
+    // SAFETY: `pthread_threadid_np` has no preconditions for current thread
+    // when pthread_t is 0 and output pointer is valid.
+    let rc = unsafe { libc::pthread_threadid_np(0, &mut tid) };
+    debug_assert_eq!(
+        rc,
+        0,
+        "pthread_threadid_np failed: {rc} ({})",
+        std::io::Error::from_raw_os_error(rc)
+    );
+    tid as i64
+}
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(target_os = "windows")]
+pub fn get_current_thread_id() -> i64 {
+    // SAFETY: GetCurrentThreadId has no preconditions.
+    unsafe { windows_sys::Win32::System::Threading::GetCurrentThreadId() as i64 }
+}
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+compile_error!("libdd_common::threading::get_current_thread_id is unsupported on this platform");

libdd-profiling/benches/add_samples.rs

@@ -2,8 +2,9 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use criterion::*;
+use libdd_common::threading::get_current_thread_id;
 use libdd_profiling::api2::Location2;
-use libdd_profiling::profiles::datatypes::{Function, FunctionId2, MappingId2};
+use libdd_profiling::profiles::datatypes::{Function, FunctionId2, MappingId2, StringId2};
 use libdd_profiling::{self as profiling, api, api2};
 
 fn make_sample_types() -> Vec<api::SampleType> {
@@ -103,6 +104,14 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
 
     let strings = dict.strings();
     let functions = dict.functions();
+    let thread_id = get_current_thread_id();
+    let thread_id_key: StringId2 = strings.try_insert("thread id").unwrap().into();
+    let labels_api = vec![api::Label {
+        key: "thread id",
+        str: "",
+        num: thread_id,
+        num_unit: "",
+    }];
 
     let frames2 = frames.map(|f| {
         let set_id = functions
@@ -127,7 +136,7 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
                 let sample = api::Sample {
                     locations: locations.clone(),
                     values: &values,
-                    labels: vec![],
+                    labels: labels_api.clone(),
                 };
                 black_box(profile.try_add_sample(sample, None)).unwrap();
             }
@@ -145,8 +154,7 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
             .unwrap();
             let (locations, values) = make_stack_api2(frames2.as_slice());
             for _ in 0..1000 {
-                // Provide an empty iterator for labels conversion path
-                let labels_iter = std::iter::empty::<anyhow::Result<api2::Label>>();
+                let labels_iter = [Ok(api2::Label::num(thread_id_key, thread_id, ""))].into_iter();
                 // SAFETY: all ids come from the profile's dictionary.
                 black_box(unsafe {
                     profile.try_add_sample2(&locations, &values, labels_iter, None)