From a0790bc050dd57765f005fc6fe6dc34e59fbbfe4 Mon Sep 17 00:00:00 2001
From: Iain McGinniss <309153+iainmcgin@users.noreply.github.com>
Date: Wed, 29 Apr 2026 20:10:59 +0000
Subject: [PATCH] build: enable lto + codegen-units=1 for release profile (#60)

Shrinks the prebuilt protoc-gen-buffa* release binaries by ~20% at the
cost of ~2x clean release-build time. Only the workspace root profile is
set (Cargo ignores per-crate profile sections inside a workspace, and the
warning noise outweighs the cargo-install benefit); the guide documents
the CARGO_PROFILE_RELEASE_LTO env-var path for cargo install users, and
the CHANGELOG notes that library consumers do not inherit this.
---
 CHANGELOG.md  | 11 +++++++++++
 Cargo.toml    |  8 ++++++++
 docs/guide.md |  7 +++++++
 3 files changed, 26 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 621c695..8a31af2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,17 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 ## [Unreleased]
 
+### Changed
+
+- The workspace `[profile.release]` now sets `lto = true` and
+  `codegen-units = 1`. This shrinks the prebuilt `protoc-gen-buffa` /
+  `protoc-gen-buffa-packaging` release binaries by roughly 20% at the cost of
+  ~2× clean release-build time. Cargo only honors profile sections from the
+  top-level workspace, so library consumers of `buffa` / `buffa-build` do not
+  inherit this — set `[profile.release]` in your own workspace (or
+  `CARGO_PROFILE_RELEASE_LTO=true` for `cargo install`) to get the same
+  benefit. ([#60](https://github.com/anthropics/buffa/issues/60))
+
 ### Fixed
 
 - `write_to` now emits fields in ascending field-number order regardless of
diff --git a/Cargo.toml b/Cargo.toml
index 29afb6d..259fb65 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -31,6 +31,14 @@ repository = "https://github.com/anthropics/buffa"
 keywords = ["protobuf", "protocol-buffers", "serialization", "no-std", "editions"]
 categories = ["encoding", "no-std"]
 
+# Applies to release builds within this workspace (CI-built release binaries,
+# benchmarks, conformance). Library consumers do not inherit this — Cargo only
+# honors [profile.*] from the top-level workspace, so a project depending on
+# buffa/buffa-build must set its own [profile.release] to get LTO.
+[profile.release]
+lto = true
+codegen-units = 1
+
 [workspace.dependencies]
 buffa = { path = "buffa", version = "0.4.0", default-features = false }
 buffa-types = { path = "buffa-types", version = "0.4.0" }
diff --git a/docs/guide.md b/docs/guide.md
index 9954766..339affe 100644
--- a/docs/guide.md
+++ b/docs/guide.md
@@ -283,6 +283,13 @@ From crates.io (recommended):
 cargo install --locked protoc-gen-buffa protoc-gen-buffa-packaging
 ```
 
+`cargo install` builds with its own default release profile, so the workspace's `lto = true` / `codegen-units = 1` settings (used for the prebuilt release binaries below) are not applied. For the smallest binary, set them via the environment:
+
+```sh
+CARGO_PROFILE_RELEASE_LTO=true CARGO_PROFILE_RELEASE_CODEGEN_UNITS=1 \
+    cargo install --locked protoc-gen-buffa protoc-gen-buffa-packaging
+```
+
 Or from a git ref, for unreleased changes:
 
 ```sh