Bun riscv64 patches

This directory holds the Bun-side patches that have to land on top of oven-sh/bun @ ${BUN_TAG} (see ../bun-version.json:bun.tag) so the build system accepts riscv64-linux-musl as a target.

build.sh applies every *.patch in this directory in lexical order via git am --3way inside the Bun clone.

Why these are needed

Bun's TypeScript build driver explicitly types its Arch as "x64" | "aarch64" (scripts/build/config.ts). Every codepath downstream of that — flag selection, CMake processor name, Rust target triple derivation, dependency build configs — branches on those two values. We need a small series of patches to:

Required patch areas

1. scripts/build/config.ts

   • Extend Arch = "x64" | "aarch64" → Arch = "x64" | "aarch64" | "riscv64".
   • In detectHost(), accept arch === 'riscv64'. (We only run the build driver under cross-compile from an x86_64 host, so this is mostly defensive — but the resolveConfig path goes through detectHost for build-time host introspection too.)
   • Add cfg.riscv64: boolean to the Config interface so dep configs can switch on it ergonomically.

2. scripts/build/flags.ts

   • In cpuTargetFlags, add a riscv64 entry that emits -march=rv64gc -mabi=lp64d. (Match what the Docker wrappers already pass — defense in depth, since cpuTargetFlags is applied late and overrides the wrapper's defaults if the wrapper-supplied flags get filtered out anywhere.)

3. scripts/build/rust.ts

   • allRustTargets already covers riscv64gc-unknown-linux-musl as a Tier-2 prebuilt-std target, but verify the host→rust-triple mapping emits it when cfg.riscv64 is true.

4. scripts/build/deps/webkit.ts

   • The prebuilt-tarball URL constructor maps arch to "amd64" | "arm64" only. For riscv64, force cfg.webkit === "local" (Bun's WEBKIT_PATH env-var path) and disable the prebuilt branch — there is no upstream oven-sh/WebKit tarball for riscv64 and there never will be unless they publish one. build.sh already exports BUN_WEBKIT_PATH pointing at the freshly built WebKitBuild/riscv64-Release/, so the local-mode path is the only one we need to reach.

5. scripts/build/deps/tinycc.ts

   • The oven-sh/tinycc fork has no riscv64 backend. Gate the dep with enabled: cfg => cfg.tinycc && !cfg.riscv64. The runtime config flag already follows: bun:ffi's JIT-compile path becomes unavailable on riscv64, but static FFI bindings still work. This is acceptable for the Android agent runtime — BUN_DISABLE_TINYCC=1 in build.sh's env also enforces this through Bun's own toggle.

6. scripts/build/bd.ts (or wherever build:release lives)

   • Accept --arch=riscv64 --abi=musl and thread it through to the cmake invocation. The --webkit-path=... flag should already work unmodified; double-check it's not gated by arch.

7. CMakeLists.txt (top-level)

   • Wherever CMAKE_SYSTEM_PROCESSOR is normalized (search for aarch64 / arm64 matches), add a riscv64 branch that sets BUN_CPU=riscv64 and emits the correct -march/-mabi. If the project gates entire compilation units behind BUN_CPU (some vendored deps' CMakeLists do), add riscv64 to the allowlist.

Optional patch areas

8. vendor/bun-uws/uSockets/CMakeLists.txt (and other vendored libs)
   • Most vendored C/C++ deps will Just Work with riscv64 since they consume CMAKE_C_COMPILER directly. Anything that grep'es CMAKE_SYSTEM_PROCESSOR STREQUAL "aarch64" to enable assembly fast-paths should add a riscv64 branch that falls back to the portable C implementation. Examples to check:
     • mimalloc (MI_ARCH switch) — falls back fine.
     • boringssl — Bun uses C fallbacks on non-x86 already.
     • lol-html (Rust) — uses target features from cargo, no patches.

Realized patch series (against bun-v1.3.13)

Note on the original task brief: Bun 1.3.x removed the top-level CMakeLists.txt — the build is now fully driven by scripts/build.ts through ninja directly. There is no cmake/ directory to patch, so "patch #7 CMakeLists.txt processor normalization" from the original brief was obsolete and is collapsed into 0007 (the per-dep audit).

Likewise the .cargo/config.toml patch is unneeded: lol-html is the only cargo-built dep, and patch 0007 sets rustTarget = riscv64gc-unknown-linux-${cfg.abi} directly. cargo finds the cross-clang via the wrapper script in the Docker image's /opt/cross/.

Verifying

cd ../  # to bun-riscv64/
./validate.sh

Runs git apply --check against a shallow clone of oven-sh/bun @ bun-v1.3.13. See ../README.md for output details.