xbjfk / mkcross

Easily create a cross compile toolchain using the host clang

mkcross

mkcross is a super fast python toolkit to make linux and windows (mingw) toolchains in seconds

Comparision (12900kf, aarch64-linux-musl)

Program	Supported targets	Time to compile aarch64-linux-musl (including downloads)	program itself can run without being configured	Programmed in	Multi target in one command
mkcross	Musl/Linux, Mingw/Windows, Picolibc/Baremetal	30s (90s)	✅	Python, C++	✅
musl-cross-make	Musl/Linux	176s (197s)	✅	Shell, Makefile	❌
crosstool-ng	uClibc/Linux GNU/Linux Newlib/Baremetal	N/A - no musl support	❌	Makefile	❌

Features

• Extremely fast.
• Portable sysroots - you can mv the sysroot anywhere you want and it will still work.
• Supports Windows, Linux, Baremetal, and - experimentally - WasiX.
• Supports every architecture LLVM supports.
• No need to compile a whole compiler for your target
  • Much faster to compile just compiler-rt, libc, libc++ than binutils, gcc and libc.
  • No need to fiddle with binutils' and gcc's autoconf
• Sysroots can be used on any machine with clang and LLVM tools installed.

How to use

Clang

Simply run clang like this:

clang --config-system-dir=[Path to sysroot]/etc/mkcross/clang

CMake

Run cmake with -DCMAKE_TOOLCHAIN_FILE=[Path to sysroot]/etc/mkcross/toolchain.cmake

How to make sysroot?

run mkcross --target=<triple>

How?

• LLVM is a cross compiler by nature. If you feed it the correct libraries, it will happily output what you want. This program will download and/or compile the needed libraries. There is no need to download/compile a whole compiler.

Notice

• wasix support is currently highly experimental
• baremetal c++ is WIP and may not work on every architecture.

What's next?

• WasiX support (EXPERIMENTAL)
• Windows target support
  • MingW
  • Proprietary (Visual Studio)
• FreeBSD
  • Prebuilt (base.tar)
  • From sources (src.tar)
  • Mix (one of above + upstream LLVM)
• MacOS target support
  • Some free software way
  • Proprietary (XCode.xip)
• Linux
  • musl
  • uclibc
  • glibc (cannot yet be built with clang)
• Bare metal (EXPERIMENTAL)
• Common libraries - zlib, curl, openssl
• More architectures in compiler RT
  • Upstream to LLVM
• Parallel download and source extraction
• Parallel target generation
  • Will require copying autoconf/symlinking source files.
• Query github api for source tarball size when download.
• Better config and yaml config for target
• Github actions to compile common targets
• Meson support (depends on this)

Notes

• mingw targets are not abi compatible with gcc mingw! They are however compatible with MSVC, including C++, thanks to the efforts of Google.

Troubleshooting tips

I get errors when compiling c++ statically!

You need to link with more c++ libs: -lc++abi and potentially -lunwind

relocation R_RISCV_HI20 out of range: 524288 is not in [-524288, 524287];

You cant compile with LTO. I need to investigate this further. If you care about the details, see this blog post

strtoll_l strtoull_l strtof_l strtod_l strtold_l etc. are undefined on picolibc:

Add -D_GNU_SOURCE to your defines.