Support riscv64 platform

[rise0chen]

400 Binary wheel 'xxxxx-cp37-abi3-musllinux_1_2_riscv64.whl' has an unsupported platform tag 'musllinux_1_2_riscv64'.

[woodruffw]

Hey @rise0chen, you're seeing this because musllinux_1_2_riscv64 isn't one of the wheel tags known to PyPI. Those are hard-baked here:

warehouse/warehouse/forklift/legacy.py

Lines 104 to 200 in 03a6530

	_allowed_platforms = {
	"any",
	"win32",
	"win_arm64",
	"win_amd64",
	"win_ia64",
	"manylinux1_x86_64",
	"manylinux1_i686",
	"manylinux2010_x86_64",
	"manylinux2010_i686",
	"manylinux2014_x86_64",
	"manylinux2014_i686",
	"manylinux2014_aarch64",
	"manylinux2014_armv7l",
	"manylinux2014_ppc64",
	"manylinux2014_ppc64le",
	"manylinux2014_s390x",
	"linux_armv6l",
	"linux_armv7l",
	}
	# macosx is a little more complicated:
	_macosx_platform_re = re.compile(r"macosx_(?P<major>\d+)_(\d+)_(?P<arch>.*)")
	_macosx_arches = {
	"ppc",
	"ppc64",
	"i386",
	"x86_64",
	"arm64",
	"intel",
	"fat",
	"fat3",
	"fat64",
	"universal",
	"universal2",
	}
	_macosx_major_versions = {
	"10",
	"11",
	"12",
	"13",
	"14",
	"15",
	}
	_ios_platform_re = re.compile(
	r"ios_(\d+)_(\d+)_(?P<arch>.*)_(iphoneos|iphonesimulator)"
	)
	_ios_arches = {
	"arm64",
	"x86_64",
	}
	_android_platform_re = re.compile(r"android_(\d+)_(?P<arch>.*)")
	_android_arches = {
	"armeabi_v7a",
	"arm64_v8a",
	"x86",
	"x86_64",
	}
	# manylinux pep600 and musllinux pep656 are a little more complicated:
	_linux_platform_re = re.compile(r"(?P<libc>(many|musl))linux_(\d+)_(\d+)_(?P<arch>.*)")
	_jointlinux_arches = {
	"x86_64",
	"i686",
	"aarch64",
	"armv7l",
	"ppc64le",
	"s390x",
	}
	_manylinux_arches = _jointlinux_arches | {"ppc64"}
	_musllinux_arches = _jointlinux_arches
	# Actual checking code;
	def _valid_platform_tag(platform_tag):
	if platform_tag in _allowed_platforms:
	return True
	m = _macosx_platform_re.match(platform_tag)
	if (
	m
	and m.group("major") in _macosx_major_versions
	and m.group("arch") in _macosx_arches
	):
	return True
	m = _linux_platform_re.match(platform_tag)
	if m and m.group("libc") == "musl":
	return m.group("arch") in _musllinux_arches
	if m and m.group("libc") == "many":
	return m.group("arch") in _manylinux_arches
	m = _ios_platform_re.match(platform_tag)
	if m and m.group("arch") in _ios_arches:
	return True
	m = _android_platform_re.match(platform_tag)
	if m and m.group("arch") in _android_arches:
	return True
	return False

The reason for this is that PyPI generally only accepts wheels for architecture tags that meet at least one of two qualifications:

1. They have a python.org binary release, which establishes a "ground truth" for ABI compatibility on that architecture;
2. They have an ABI specification (typically in the form of a PEP) that explains what binary compatibility for wheels on that platform entails.

My understanding is that neither of these is true for riscv64 at the moment.

I took a quick look, and the discussion for the standards side of riscv64 wheels appears to have begun here: https://discuss.python.org/t/packaging-support-for-riscv64/58475

TL;DR: I suspect this is blocked on larger standards changes that would enable riscv64 wheels to be reliably accounted for in terms of tags + ABI compatibility.

[zanieb]

It's worth noting that we attempted to release this in uv and got bit by the lack of support in PyPI (astral-sh/uv#14007)

Support for this architecture in the ecosystem is growing, e.g., Maturin supports riscv64 (PyO3/maturin#1001, a Python binary is available via python-build-standalone (astral-sh/python-build-standalone#491), and auditwheel supports riscv64 manylinux wheels (https://github.com/pypa/auditwheel/blob/763366ae5060a63655b2209912fb8300dd13339d/src/auditwheel/policy/manylinux-policy.json#L361-L368)

[woodruffw]

TIL, I didn't realize adoption was further along elsewhere!

So, it looks like there are two different things here -- there's manylinux for riscv64 and musllinux for riscv64. It looks like uv got snared on manylinux and @rise0chen got snared on musllinux.

(The proximate cause is the same in terms of PyPI's rejection, but the solution is a little different 😅 -- pypa/manylinux#1426 seems to have some of the blockers for manylinux and the PEP 600 process, while musllinux via PEP 656 is probably a bit more streamlined since it doesn't require the presence of official build images.)