Gcc Arm To Zig

Gcc Arm to Zig, or gatz, is both a command line program and a zig module that provides utilities for porting projects using the gcc-arm-none-eabi compiler to Zig. It is intended to be used with freestanding Arm Cortex-M targets (micro-controllers). Currently only Cortex-M targets are supported, however this could be expanded in the future if there's demand for it.

Once mature enough, this project will have releases corresponding to Zig releases. For now, this tracks Zig version 0.14.0.

Installing as a Module

Add gatz as a dependency to build.zig.zon like so:

zig fetch --save git+https://github.com/haydenridd/gcc-arm-to-zig

For using the build utilities provided in build.zig you can now add:

const gatz = @import("gatz");

If you want to use gatz in application code you can add the following to build() in build.zig:

const gatz = b.dependency("gatz", .{});
exe.root_module.addImport("gatz", gatz.module("gatz"));

Installing as a CLI

Just run zig build from root, and you should have an executable zig-out/bin/gatz!

Command Line Utility

The gatz CLI serves a dual purpose:

• Translating GCC "architecture" flags like -mcpu, -mfpu, -mfloat-abi, -mthumb/-marm to Zig target arguments
• Validating the combination of flags used (not even GCC does this!)

This utility can save a lot of time because figuring out, for example, that the following flags:

--mcpu=cortex-m7 --mfloat-abi=hard --mfpu=fpv5-sp-d16

Translate to:

-Dtarget=thumb-freestanding-eabihf -Dcpu=cortex_m7+fp_armv8d16sp

Is extremely non-trivial and involves lots of datasheet diving. With gatz this process is as simple as:

gatz --mcpu=cortex-m7 --mfloat-abi=hard --mfpu=fpv5-sp-d16
Translated `zig build` options: -Dtarget=thumb-freestanding-eabihf -Dcpu=cortex_m7+fp_armv8d16sp

It will check for invalid configurations:

gatz --mcpu=cortex-m7 --mfloat-abi=hard --mfpu=fpv2
--mfpu=fpv2 is not a valid FPU, see info command for valid FPUs

And can display valid configurations:

gatz info --mcpu=cortex-m7
CPU: cortex-m7       | Float ABIS: soft,softfp,hard | Fpu Types: vfpv4,vfpv4-d16,fpv4-sp-d16,fpv5-d16,fpv5-sp-d16

See gatz -h for full documentation.

Build Utilities

gatz provides utilities for use in a build.zig file that make things like target selection and linking in arm-none-eabi-gcc's pre-compiled Newlib libc much easier than in vanilla Zig. See the build.zig for an example project using gatz for a more detailed walkthrough.

Contributing

Github issues for feature requests/bugs are welcome! PR's are also welcome!

TODO:

• Add some dummy assembly files that excercise instructions for each possible target combo (fpu, endianness, etc.) + ensure that each target configuration can compile said assembly code
  • Add this to CI
• Expansion beyond Cortex-M targets if enough interest