macos_cross_build.md

macOS Cross Build

Source note: https://stackoverflow.com/a/76183280/9363996

Goal: cross-build the omnirefl tool for macOS from the Alpine build image.

Findings

• Existing osxcross images are available on Docker Hub.

  • liushuyu/osxcross:latest was inspected.
  • It contains /opt/osxcross/SDK/MacOSX10.14.sdk.
  • It contains o64-clang, x86_64-apple-darwin18-*, ld64, lipo, install_name_tool, and related cctools.
  • It is old: created in 2020, Clang 10, Darwin18/x86_64 oriented.
  • It bundles an Apple SDK, so it has the same SDK redistribution concern.
  • Treat as a reference/probe image, not a release base.

• Darling has an SDK-like open-source tree.

  • Repo: https://github.com/darlinghq/darling
  • Path: Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
  • C/POSIX headers are present.
  • libSystem.dylib is a symlink into Darling build output.
  • No .tbd stubs were found in the repo tree.
  • Not a drop-in SDK for release binaries, but useful for research.

• Apple open-source Darwin components are not a complete macOS SDK.

  • Repo: https://github.com/apple-oss-distributions/distribution-macOS
  • Useful source drops, not a packaged sysroot.

Required Inputs

• Apple SDK/sysroot
  • MacOSX.sdk extracted from Xcode.
  • Not an Alpine package; must be imported from a Mac/Xcode install.

Tools

• MacOSX.sdk

  • install: cannot be installed from Alpine packages
  • build: cannot be built from open source; copy/extract from Xcode or Apple Command Line Tools

• clang

  • install: Alpine clang21 / existing prebuilt LLVM image layer
  • build: https://github.com/llvm/llvm-project

• llvm-config

  • install: existing prebuilt LLVM image layer
  • build: https://github.com/llvm/llvm-project

• lld

  • install: Alpine lld21
  • build: https://github.com/llvm/llvm-project

• libc++ headers

  • install: existing generated LLVM runtimes headers in the image
  • build: https://github.com/llvm/llvm-project/tree/main/runtimes

• apple-libtapi

  • install: not available from Alpine packages
  • build: https://github.com/tpoechtrager/apple-libtapi

• xar

  • install: Alpine xar
  • build: https://github.com/tpoechtrager/xar

• cctools-port

  • install: not available from Alpine packages
  • build: https://github.com/tpoechtrager/cctools-port

• ld

  • install: built/installed by cctools-port
  • build: https://github.com/tpoechtrager/cctools-port

• ar

  • install: built/installed by cctools-port
  • build: https://github.com/tpoechtrager/cctools-port

• ranlib

  • install: built/installed by cctools-port
  • build: https://github.com/tpoechtrager/cctools-port

• strip

  • install: built/installed by cctools-port
  • build: https://github.com/tpoechtrager/cctools-port

• libtool

  • install: built/installed by cctools-port
  • build: https://github.com/tpoechtrager/cctools-port

• lipo

  • install: built/installed by cctools-port
  • build: https://github.com/tpoechtrager/cctools-port

• install_name_tool

  • install: built/installed by cctools-port
  • build: https://github.com/tpoechtrager/cctools-port

LLVM Changes

• Add AArch64 to LLVM_TARGETS_TO_BUILD for Apple Silicon.
• Consider adding lld to LLVM_ENABLE_PROJECTS.
  • May not be required if using cctools ld64.

Current Alpine image builds LLVM with LLVM_TARGETS_TO_BUILD=X86 only.

Alpine Build Dependencies

Likely needed to build the missing tools:

• bash
• autoconf
• automake
• libtool
• pkgconf
• zlib-dev
• openssl-dev
• libxml2-dev
• musl-fts-dev or equivalent

musl-fts matters because cctools-port documents musl-libc systems as needing it.