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Alice reported [1] that an arm64 build failed with:
ld.lld: error: undefined symbol: __extendsfdf2
>>> referenced by core.a6f5fc5794e7b7b3-cgu.0
>>> rust/core.o:(<f32>::midpoint) in archive vmlinux.a
>>> referenced by core.a6f5fc5794e7b7b3-cgu.0
>>> rust/core.o:(<f32>::midpoint) in archive vmlinux.a
ld.lld: error: undefined symbol: __truncdfsf2
>>> referenced by core.a6f5fc5794e7b7b3-cgu.0
>>> rust/core.o:(<f32>::midpoint) in archive vmlinux.a
Rust 1.80.0 or later together with `CONFIG_CC_OPTIMIZE_FOR_SIZE=y`
is what triggers it.
In addition, x86_64 builds also fail the same way.
Similarly, compiling with Rust 1.82.0 (currently in nightly) makes
another one appear, possibly due to the LLVM 19 upgrade there:
ld.lld: error: undefined symbol: __eqdf2
>>> referenced by core.20495ea57a9f069d-cgu.0
>>> rust/core.o:(<f64>::next_up) in archive vmlinux.a
>>> referenced by core.20495ea57a9f069d-cgu.0
>>> rust/core.o:(<f64>::next_down) in archive vmlinux.a
Gary adds [1]:
> Usually the fix on rustc side is to mark those functions as `#[inline]`
>
> All of {midpoint,next_up,next_down} are indeed unstable functions not
> marked as inline...
Fix all those by adding those intrinsics to our usual workaround.
[ Trevor quickly submitted a fix to upstream Rust [2] that has already
been merged, to be released in Rust 1.82.0 (2024-10-17). - Miguel ]
Cc: Gary Guo <gary@garyguo.net>
Reported-by: Alice Ryhl <aliceryhl@google.com>
Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/x/topic/x/near/455637364 [1]
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://github.com/rust-lang/rust/pull/128749 [2]
Link: https://lore.kernel.org/r/20240806150619.192882-1-ojeda@kernel.org
[ Shortened Zulip link. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.