`examples.nix` had settings that only repeated what the `config` already
implied. They read as if the platform were special, when it ought to be
the default. Now the default logic in `default.nix` ought to handle the
setting in question in a rule-based way so it is.
Change:
- `useLLVM` now covers
- UEFI
- MSVC CRT and C++ ABI
- Windows on AArch64 as well as FreeBSD and OpenBSD
- `libc` gains a UEFI case
hat retires seven `useLLVM` settings, eighteen `libc = "newlib"`, one
`libc = "bionic"`, and the `libc`/`linker` pair on the UEFI examples.
The remaining `libc`s in examples now means"this differs from what the
triple implies", which is true of the seven left: `newlib-nano`, the
mingw `msvcrt`/`ucrt` pairs those entries exist to distinguish, and
`mmix`, whose OS is `mmixware` rather than `none` so the bare-metal
default does not reach it. That one gains a comment.
No functional change. Elaborating all 87 platforms in
`lib.systems.examples` before and after gives byte-identical `config`,
`system`, `useLLVM`, `useGccNG`, `libc`, `linker` and
`rust.rustcTarget`. `mmix` surfaced that way, having regressed to
`native/impure`.
Assisted-by: Claude Code (Claude Opus 5)
Nothing could select the split GCC package set, so none of the fixes
below this commit were reachable from a normal build.
Add `useGccNG` alongside the existing `useLLVM`/`useZig`/`useArocc`
choices, and honour it where a compiler is picked: the cross stdenv takes
`gccNGPackages.gcc`, and `stdenvNoLibs`/`stdenvNoLibc` map to
`gccNoLibgcc` and `gccWithLibgcc`. That last pair is the point of the
split. Both currently fall back to `gccCrossLibcStdenv`, because the
monolithic compiler cannot distinguish them; `lib/systems/default.nix`
says as much next to `linker`, noting that we would like to choose the C
compiler and runtime library orthogonally but "due to the monolithic GCC
build we cannot actually make those choices independently". This is what
lifts that, the way the LLVM set already splits `clangNoCompilerRt` from
`clangNoLibc`.
`gccNGPackages` tracks `default-gcc-version` rather than naming a
release, so the split set and the monolithic `gcc` stay on the same one.
`useGccNG` defaults to `false` and no platform derives it, so no existing
build changes. Setting it on a platform spec is enough to exercise the
whole stack:
nix-build . -A stdenv.cc --arg crossSystem \
'{ config = "aarch64-unknown-linux-musl"; useGccNG = true; }'
The intent is to switch obscure low-tier platforms over to it soon --
NetBSD first -- so `ng` gets dogfooded somewhere the blast radius is
small. Those switches come separately.
Assisted-by: Claude Code (Claude Opus 5)
Wasi P2 is different enough to Wasi P1 to warrant being treated entirely
separately, rather than as two minor variants of the same thing. P3 will
likewise want to be a different target.
I've left aliases in place; maybe eventually, those can be deprecated
and removed. I've tested this, but it's possible there might be breakage
somewhere (e.g., the canonical doubles for P1 have changed, though I
can't imagine why anyone would rely on that).
Fixes https://github.com/NixOS/nixpkgs/issues/435954
This ensures that `lib.platforms.darwin` doesn’t include
`x86_64-darwin` and that the unsupported platform check will trigger
even once the bespoke deprecation error is removed. It doesn’t break
`lib.systems.elaborate "x86_64-darwin"`.
A platform elaborated by another supported revision of Nixpkgs would
trip the assertion when it is re-elaborated.
Avoid this, by checking `oldestSupportedReleaseIsAtLeast 2511`, as 25.11
is the version that stopped adding `linux-kernel` to elaborated systems.
rustc allows code to perform compile-time tests against target_env [0],
which is a function of the target triple. There isn't provision in
Nixpkgs for learning target_env, however. That doesn't affect rustc's
evaluation of cfg guards in Rust code - rustc knows perfectly well what
target_env is - but it _does_ affect the env vars passed to a build
script set by buildRustCrate, which is presently hard-coded to gnu, and
also affects any Nix code looking to branch on target_env.
Being able to access target_env is very relevant to, for example, WASI
as (using Rust terminology) wasm32-wasip1 and wasm32-wasip2 differ only
by target_env, with identical target_arch and target_os values. Properly
reflecting target_env may also fix some random musl issues if you're a
bit lucky.
This commit adds a new attr, rust.platform.env, which reflects the
target_env that rustc will set for the target, and wires it up in
buildRustCrate. In isolation, this change mostly only affects build
scripts checking target_env, but crate2nix will greatly benefit from
being able to accurately resolve the dep graph (which can also vary
depending on target_env).
The target triple -> target_env function resists Kolmogorov compression:
it's irregular and, though there are some patterns, there are lots of
special cases. So, I have done the stupidest possible thing and scraped
out all of the targets with non-empty target_env values and dumped that
into an attrset. This attrset will progressively get out of date as
rustc adds new platforms, but updating it should be simple enough - I've
included the generation script as a comment.
There are some other configuration options not being reflected in Nix. I
have left those alone, but, in the future, maybe this can be extended to
just dumping all of them into an attrset and then reflecting them in
rust.platform. It might even make sense to convert the existing code
producing rust.platform to just looking up from an attrset and to 'do
what rustc does'.
I would have liked to have added a test targetting a platform with a
non-empty non-GNU target_env, but all of the yaks were quite hairy.
Fixes https://github.com/NixOS/nixpkgs/issues/436832
[0]: https://doc.rust-lang.org/reference/conditional-compilation.html#r-cfg.target_env
Currently, you need to override `stdenv.hostPlatform` to request a
compressed kernel on AArch64, and the kernel configuration is split
between the central structured configuration and string snippets in
platform definitions. This has consequently made the latter bitrot
terribly. Since the platform‐specific logic is now very limited after
cleaning up the detritus, we can move it into the kernel derivation
and expose the relevant configuration there for anyone who wants to
customize it further or needs to read it out.
Co-authored-by: zowoq <59103226+zowoq@users.noreply.github.com>
The `sheevaplug` kernel configuration was added a very long time
ago and has not been adjusted for years. `pogoplug4` was identical
to `sheevaplug` except for an even more stripped‐down kernel
configuration, no device tree support, and a different load address
for the uImage.
These days, the stock kernel configuration builds and there has been
an upstream device tree for the Pogoplug Series 4 for years; unify
`sheevaplug` and `pogoplug4` into an `armv5tel-multiplatform` that
uses the standard configuration.
ARMv5 was also the only platform that defaulted to uImage, the [legacy
U‐Boot image format] that is deprecated upstream. Our bootloader
machinery in NixOS does not handle these images in any special way
and even the original ARMv6 Raspberry Pi platform defaults to the
standard zImage. We switch `armv5tel-multiplatform` to zImage to match.
[legacy U‐Boot image format]: https://docs.u-boot.org/en/latest/usage/cmd/bootm.html#legacy-boot
It is of course natural to worry about backwards compatibility
here: this switches to a different kernel image format and drops
support for root on NFS along with random oddities like KGDB and
LatencyTOP. Renaming the platform is intended to help mitigate
this risk.
The reality, however, is that it is currently very
difficult to build a configuration for ARMv5. I found
<https://github.com/thefloweringash/sheevaplug-nix> online as
an example configuration from many years ago; it already set
`autoModules`, and builds U‐Boot using `CONFIG_DISTRO_DEFAULTS`,
which should work out of the box without requiring the legacy U‐Boot
image format.
Even then, however, I confirmed with the author that it hasn’t
been used in years, and I could barely get it to build with
a modern Nixpkgs: OpenSSH is broken, Nix is broken, multiple
default `environment.systemPackages` in the SD image profile
are broken, `boot.initrd.includeDefaultModules` is broken, and
`hardware.enableAllHardware` is broken.
I conclude that if anyone is actively building systems on ARMv5, they
have a forked Nixpkgs or a very custom setup. Given our general move
to standard boot chains and no platform‐specific hacks, and the
decaying state of our unofficial support for 32‐bit ARM, I think
it is not worth maintaining support for the legacy image format for
this one ancient platform.
If anyone is running a heavily stripped‐down NixOS configuration on
mission‐critical SheevaPlugs using a custom Nix‐free deployment
setup relying on the legacy U‐Boot image format and somehow none
of these kernel changes manage to loudly break their build, hopefully
they’ll at least notice the release notes entry! Otherwise there’s
always JTAG…
These were not used by the selection logic or
`lib/systems/examples.nix`, so any consumer would have to be including
them explicitly. Since we’re moving away from setting Linux kernel
configuration in the platform structure, breaking these explictily
won’t reduce the convenience and will help signal to any such expert
users that they need to move their kernel configuration elsewhere.
None of these successfully build a kernel, and as we’re moving
away from putting kernel configuration in the platform structure and
don’t package the vendor kernels that all but `fuloong2f_n32` expect,
there’s no point to keeping these kernel configurations in Nixpkgs.
