#Porting Hare to your OS

Hare upstream expects to use ELF. You can work around this but YMMV.

The standard library expects a reasonably Unix-like environment. However, you can build your own standard library relatively easily and vendor or fork various portable bits of the stdlib. This can go a long ways, Mercury does this and provides a comfortable Hare environment with relatively little effort.

#Cross compiling

Configure Hare for your build host normally:

https://harelang.org/installation/

Then start porting the standard library. Start by porting rt, the runtime. The minimal port requires your target support code at rt/+target. Add the following:

• An entry point at rt/+target/start+$arch.s
• Optional platform-specific entry code at rt/+target/platformstart.ha
  • On Linux this is where the auxillary vector is loaded
  • Should call the portable start_ha function to finish startup
  • If you don't want/need this just have your entry point branch to start_ha
• Add rt/+target/syscallno.ha/syscalls.ha as appropriate for your target. You don't need to write wrappers for all syscalls just yet.
• Implement rt/+target/segmalloc.ha, to hook up the allocator to your target's mmap or equivalent
• Linker script at rt/hare+target.sc if rt/hare.sc is not suitable for your platform

This should be sufficient to build simple Hare programs that use syscall wrappers directly, such as this one for Linux:

use rt;

export fn main() void = {
	const bytes = tobytes("Hello world!\n");
	rt::write(0, &bytes[0], len(bytes))!;
};

fn tobytes(s: str) []u8 = *(&s: *[]u8);

You can cross-compile this for your target like so:

$ hare build -o example -X^ -T+target [-t $arch] main.ha

Then port other stdlib modules as you see fit. Many modules, such as bytes or ascii, are portable. Others, such as crypto and time, are mostly portable. Some are not portable and will need to be ported to your target, including notably:

• io
• net
• os
• temp
• unix

Good luck!

#Native toolchain

You need:

• A C11 toolchain, including binutils
• A reasonable subset of POSIX

The steps are:

1. Port qbe to your target
2. Port harec to your target
3. Port the minimal rt to your target
   • Update rt/configure as necessary
   • mkdir rt/+target
   • Write an entry point at rt/+target/start+$arch.s
   • Add syscall wrappers and other required bits
4. Get the test suite to pass