rust build of 1.47.0: rustdoc fails when cross-building for NetBSD/sparc64

[he32]

While building for NetBSD/sparc64 with NetBSD/amd64 as host, I reproducibly encounter this error:

 Documenting std v0.0.0 (/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/library/std)
error: `crate::os::linux::raw::stat` is both a struct and a function
  --> library/std/src/os/linux/fs.rs:21:19
   |
21 |     /// [`stat`]: crate::os::linux::raw::stat
   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^ ambiguous link
   |
   = note: `-D broken-intra-doc-links` implied by `-D warnings`
help: to link to the struct, prefix with the item type
   |
21 |     /// [`stat`]: struct@crate::os::linux::raw::stat
   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: to link to the function, add parentheses
   |
21 |     /// [`stat`]: crate::os::linux::raw::stat()
   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

error: Could not document `std`.

...and since this is an error, the whole build fails. Trying to append () to the
string as suggested just produces another error, so is obviously not the right thing to do.

Oddly, when building natively on NetBSD/amd64, this error is not flagged.
Also, when cross-building for NetBSD/macppc or NetBSD/armv7 on NetBSD/amd64,
this error is also not flagged.

I expected to see the build complete without errors; 1.46.0 certainly did.

Yes, we carry a number of patches to rust in pkgsrc, not all of them up-streamable...

Still, hints for what might be the root cause of this failure are most welcome,
or how I might work around this issue.

It seems odd that it's complaining about what on the face of it appears to be a
Linux-specific function when this isn't run on or being built for Linux...

Meta

rustc --version --verbose:

rustc 1.46.0 (04488afe3 2020-08-24)
binary: rustc
commit-hash: 04488afe34512aa4c33566eb16d8c912a3ae04f9
commit-date: 2020-08-24
host: x86_64-unknown-netbsd
release: 1.46.0
LLVM version: 10.0

(That's the bootstrap version used.)

Backtrace

Caused by:
  process didn't exit successfully: `/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/bootstrap/debug/rustdoc --edition=2018 --crate-type dylib --crate-type rlib --crate-name std library/std/src/lib.rs --target sparc64-unknown-netbsd -o /usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/doc --cfg 'feature="addr2line"' --cfg 'feature="backtrace"' --cfg 'feature="compiler-builtins-c"' --cfg 'feature="gimli-symbolize"' --cfg 'feature="miniz_oxide"' --cfg 'feature="object"' --cfg 'feature="panic_unwind"' --cfg 'feature="std_detect_dlsym_getauxval"' --cfg 'feature="std_detect_file_io"' --error-format=json --json=diagnostic-rendered-ansi --markdown-css rust.css --markdown-no-toc -Z unstable-options --resource-suffix 1.47.0 --index-page /usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/src/doc/index.md -L dependency=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps -L dependency=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/release/deps --extern addr2line=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libaddr2line-03cb55b7425d7dbb.rmeta --extern alloc=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/liballoc-455bc16b9b6b4424.rmeta --extern cfg_if=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libcfg_if-7fc54f1c23911eb1.rmeta --extern compiler_builtins=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libcompiler_builtins-317780efb78c97c5.rmeta --extern core=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libcore-0f5f9e2fc8fc9f24.rmeta --extern hashbrown=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libhashbrown-943e711081285abb.rmeta --extern libc=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/liblibc-3b8680b5a3769d54.rmeta --extern miniz_oxide=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libminiz_oxide-3fbd2f81c64e7314.rmeta --extern object=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libobject-b55e8f81947c9d81.rmeta --extern panic_abort=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libpanic_abort-83aafb0d29c77dec.rmeta --extern panic_unwind=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libpanic_unwind-5427c3db55291636.rmeta --extern rustc_demangle=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/librustc_demangle-de5e000b109f02c7.rmeta --extern unwind=/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/x86_64-unknown-netbsd/stage2-std/sparc64-unknown-netbsd/release/deps/libunwind-478e4996ad0d78a7.rmeta -Dwarnings -Winvalid_codeblock_attributes --crate-version 1.47.0 --cfg backtrace_in_libstd` (exit code: 1)


command did not execute successfully: "/usr/pkgsrc/lang/rust/work/rust-bootstrap/bin/cargo" "rustdoc" "--target" "sparc64-unknown-netbsd" "-Zbinary-dep-depinfo" "-j" "4" "--release" "--frozen" "--features" "panic-unwind backtrace compiler-builtins-c" "--manifest-path" "/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/library/test/Cargo.toml" "-p" "std" "--" "--markdown-css" "rust.css" "--markdown-no-toc" "-Z" "unstable-options" "--resource-suffix" "1.47.0" "--index-page" "/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/src/doc/index.md"
expected success, got: exit code: 101


Traceback (most recent call last):
  File "./x.py", line 11, in <module>
    bootstrap.main()
  File "/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/src/bootstrap/bootstrap.py", line 1016, in main
    bootstrap(help_triggered)
  File "/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/src/bootstrap/bootstrap.py", line 1002, in bootstrap
    run(args, env=env, verbose=build.verbose)
  File "/usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/src/bootstrap/bootstrap.py", line 143, in run
    raise RuntimeError(err)
RuntimeError: failed to run: /usr/pkgsrc/lang/rust/work/rustc-1.47.0-src/build/bootstrap/debug/bootstrap -v dist -j 4

[Mark-Simulacrum]

Are you self-bootstrapping the cross build (setting rustc/cargo 1.47 as well)? I guess that's the only difference I can think of that would obviously cause things like this.

It's also possible this is just always broken, rust-lang/rust doesn't cross-compile documentation I think for most platforms so we don't really test it.

[Mark-Simulacrum]

cc @jyn514

[jyn514]

The easiest way to fix this is just to disambiguate the intra-doc link: struct@crate::os::linux::raw::stat.

...and since this is an error, the whole build fails.

I highly recommend setting disable-warnings = true, I don't think rustc guarantees at all that it will build without warnings when cross-compiled.

[jyn514]

See also #76526.

[he32]

Are you self-bootstrapping the cross build (setting rustc/cargo 1.47 as well)? I guess that's the only difference I can think of that would obviously cause things like this.

Nor sure I fully understand the question. The bootstrap compiler is 1.46.0, but it looks like in this instance it's the built-as-part-of-bootstrap rustdoc from 1.47 that's being run. My build is started with

${PYTHONBIN} ./x.py -v dist -j 4

and just prior to the error the build log contains

    c Rustdoc { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-unknown-netbsd", file: None } } }

so this is done as part of the stage 2 of the bootstrap.

It's also possible this is just always broken, rust-lang/rust doesn't cross-compile documentation I think for most platforms so we don't really test it.

Hm. "Room for improvement!" :)

[he32]

The easiest way to fix this is just to disambiguate the intra-doc link: struct@crate::os::linux::raw::stat.

Thanks, that worked. Silly of me not trying that variant first...

...and since this is an error, the whole build fails.

I highly recommend setting disable-warnings = true, I don't think rustc guarantees at all that it will build without warnings when cross-compiled.

Is this really supposed to be deny-warnings = false in config.toml? (Default appears to be true)

[jyn514]

Yes, thanks, I meant = false.

Are you interested in making a PR with the struct@ fix so this is fixed for others too? :)

[cuviper]

I already fixed this one in #77777.

[jyn514]

Great, so this is fixed in nightly then.