Previously, it wasn't possible to access the list of platforms we can
build Rust programs for outside of buildRustPackage. This was a
problem for packages that have optional Rust components, like
gstreamer or Meson, as there was no way to only build the Rust parts
for supported platforms. Now it's possible to get that information
from rustc's passthru.
We need to set -crt-static on musl for rustdoc as well, so let's unify
the wrappers. Ideally, rather than wrapping rustdoc, we'd have
rustdoc use the wrapped rustc, but that's currently only possible with
an unstable option (--test-builder).
The options set by the wrapper, -C target-feature and --sysroot, are
supported by both rustdoc and rustc, but other flags maybe not be
supported by both, so I've introduced different environment
variables (the existing NIX_RUSTFLAGS and a new NIX_RUSTDOCFLAGS) to
allow those to be set independently.
This fixes cargo-auditable in pkgsMusl., which broke because its
doctests stopped working when -crt-static was moved to the wrapper.
Fixes: 79156bf13a ("rustc: move crt-static default override to wrapper (#291829)")
Previously, when cross compiling from non-musl to musl, the crt-static
default override wouldn't be applied, because the compiler wouldn't
have been built with it due to fastCross. Moving it to the wrapper
fixes this without having to introduce extra compiler rebuilds. And
because the wrapper is applied even to the bootstrap rustc, we no
longer need special handling of crt-static in the Cargo expression.
Unlike --sysroot, rustc allows -C target-feature= to be passed
multiple times, with later instances taking precedence over earlier
ones. This means that it's very easy to set the default in the
wrapper, just by our overridden default before any other arguments.
This fixes pkgsCross.aarch64-multiplatform-musl.mesa from x86_64-linux.
It turns out that unlike a normal Unix program, if the --sysroot
option is given more than once, rustc will error rather than using the
last value given. Therefore, we need to ensure we only add our
default --sysroot argument if one hasn't been given explicitly on the
wrapper's command line.
This fixes cross compilation of rustc.
Closes: https://github.com/NixOS/nixpkgs/issues/271736
Fixes: 8b51cdd3be ("rustc: add a compiler wrapper")
We keep running into situations where we can't get the right
combination of rustc flags through build systems into rustc.
RUSTFLAGS is the only variable supported across build systems, but if
RUSTFLAGS is set, Cargo will ignore all other ways of specifying rustc
flags, including the target-specific ones, which we need to make
dynamic musl builds work. (This is why pkgsCross.musl64.crosvm is
currently broken — it works if you unset separateDebugInfo, which
causes RUSTFLAGS not to be set.)
So, we need to do the same thing we do for C and C++ compilers, and
add a compiler wrapper so we can inject the flags we need, regardless
of the build system.
Currently the wrapper only supports a single mechanism for injecting
flags — the NIX_RUSTFLAGS environment variable. As time goes on,
we'll probably want to add additional features, like target-specific
environment variables.
