Note macos/win behavior is not standardized

Author: cataphract

libdd-library-config/src/otel_process_ctx.rs

@@ -2,7 +2,14 @@
 // SPDX-License-Identifier: Apache-2.0
 
 //! Implementation of the [OTEL process
-//! context specification](https://github.com/open-telemetry/opentelemetry-specification/pull/4719).
+//! context specification](https://github.com/open-telemetry/opentelemetry-specification/blob/main/oteps/profiles/4719-process-ctx.md).
+//!
+//! Note: the Linux implementation follows the discovery method described in the OTEL process
+//! specification linked above, that is, uses a memfd or a named mapping with the name OTEL_CTX.
+//! This is a strategy only viable on Linux, since MacOS and Windows do not have those exact
+//! features. Here, the MacOS and Windows implementations, on the other hand, use a global atomic
+//! pointer to the mapping header that is published as a symbol named `otel_process_ctx_v2`.
+//! SUCH MECHANISM IS NOT PART OF THE SPECIFICATION, which deals only with Linux.
 //!
 //! The update/read protocol is seqlock-style: the publisher marks the mapping as unavailable,
 //! writes the payload metadata, publishes a non-zero version, and readers accept a copy only if

libdd-library-config/src/otel_process_ctx/writer/macos.rs

@@ -1,6 +1,9 @@
 // Copyright 2026-Present Datadog, Inc. https://www.datadoghq.com/
 // SPDX-License-Identifier: Apache-2.0
 
+//! Implements the publication strategy for MacOS.
+//! This is not part of the OTEL process context specification, which deals only with Linux.
+
 use core::{
     ffi::c_void,
     mem::forget,

libdd-library-config/src/otel_process_ctx/writer/windows.rs

@@ -1,6 +1,9 @@
 // Copyright 2026-Present Datadog, Inc. https://www.datadoghq.com/
 // SPDX-License-Identifier: Apache-2.0
 
+//! Implements the publication strategy for Windows.
+//! This is not part of the OTEL process context specification, which deals only with Linux.
+
 use core::{
     ptr::{self, NonNull},
     sync::atomic::{fence, AtomicPtr, AtomicU32, AtomicU64, Ordering},