Protobuf 3 Vendoring Implementation Plan

For agentic workers: REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (- [ ]) syntax for tracking.

Goal: Vendor protobuf 3 into deps/ and make the mysqlx plugin link against it on Linux and macOS without depending on Homebrew or the system libprotobuf.

Architecture: Add a protobuf 3 source archive and a small deps/Makefile recipe that builds a static libprotobuf.a from that archive into a local deps/protobuf build tree. Then update plugins/mysqlx/Makefile so the plugin uses the vendored protobuf include and library paths unconditionally on both Linux and macOS, while keeping the existing generated *.pb.cc sources unchanged.

Tech Stack: GNU make, CMake, C++17, protobuf 3.21.12 source release.

Task 1: Add vendored protobuf source and build recipe

Files:

Create: deps/protobuf/protobuf-3.21.12.tar.gz
Modify: deps/Makefile
Step 1: Add the protobuf source archive

Download https://github.com/protocolbuffers/protobuf/releases/download/v3.21.12/protobuf-3.21.12.tar.gz into deps/protobuf/.

Step 2: Add a failing build target

Extend deps/Makefile with a protobuf target that extracts the archive and runs a CMake build for a static runtime library. The target should produce a stable artifact path that other makefiles can consume, such as deps/protobuf/protobuf-3.21.12/build/libprotobuf.a or a local install tree under deps/protobuf/install/.

Step 3: Run the dependency build

Run: make -C deps protobuf -j24

Expected: protobuf 3.21.12 configures and builds a static runtime library without touching the mysqlx plugin yet.

Step 4: Commit

bash

git add deps/protobuf/protobuf-3.21.12.tar.gz deps/Makefile
git commit -m "Vendor protobuf 3 for mysqlx"

Task 2: Link mysqlx against vendored protobuf

Files:

Modify: plugins/mysqlx/Makefile
Step 1: Update the mysqlx build inputs

Replace the pkg-config protobuf dependency check with explicit include/library paths that point at the vendored protobuf build or install tree from Task 1. Keep the existing PROTOBUF_GENERATED_VERSION := 3.21.12 guard so the build still fails if the archive is missing or the wrong protobuf tree is selected.

Step 2: Build the plugin on Linux

Run: make -C plugins/mysqlx PROXYSQL40=1 -j24

Expected: the plugin links successfully against the vendored libprotobuf.a.

Step 3: Build the plugin on macOS

Run the same make -C plugins/mysqlx PROXYSQL40=1 -j24 flow on macOS.

Expected: the build no longer depends on Homebrew protobuf@3 and does not trip the ABI guard.

Step 4: Commit

bash

git add plugins/mysqlx/Makefile
git commit -m "Link mysqlx against vendored protobuf"

Task 3: Verify the full build

Files:

None
Step 1: Rebuild the tree

Run:

bash

export PROXYSQL40=1
make cleanall
make build_deps -j24
make debug -j24
make build_tap_test_debug -j24

Expected: the full Linux build passes with vendored protobuf and the mysqlx plugin still builds.

Step 2: Inspect any remaining platform-specific warnings

If the macOS build reveals any path or linker differences, adjust only the vendored protobuf wiring rather than reintroducing a system-protobuf dependency.

Step 3: Commit verification notes

Record the exact commands and any residual warnings in the branch notes or PR description.