Error when building with panic = "abort" and -Z build-std

[dalcde]

EDIT: The same happens with building an (empty) binary crate with panic = "abort" and -Z build-std, without cross-compilation

Create an empty library crate with crate-type = ["cdylib"]. Then attempt to build with

cargo +nightly build -Z build-std --target wasm32-unknown-unknown

Then you get lots of errors of the form

error: duplicate lang item in crate `core`: `RangeToInclusive`.
  |
  = note: the lang item is first defined in crate `core` (which `std` depends on)
  = note: first definition in `core` loaded from /tmp/foobar/target/wasm32-unknown-unknown/debug/deps/libcore-7e733f1b75b6332e.rlib, /tmp/foobar/target/wasm32-unknown-unknown/debug/deps/libcore-7e733f1b75b6332e.rmeta
  = note: second definition in `core` loaded from /home/$USER/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-unknown/lib/libcore-73412d1456c20040.rlib

This works if either cdylib, build-std or cross-compiling to wasm32-unknown-unknown is removed. I have not attempted to cross-compile to other architectures.

Meta

This is using rustc 1.51.0-nightly (80184183b 2021-01-03)

[dalcde]

I tried to rmove the directory /home/$USER/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-unknown/lib/libcore-73412d1456c20040.rlib. What I get is

...
   Compiling test_ v0.1.0 (/tmp/test_)
error[E0463]: can't find crate for `panic_abort`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0463`.
error: could not compile `test_`

To learn more, run the command again with --verbose.

[dalcde]

Running cargo build with -v gives

Running `rustc --crate-name test_ --edition=2018 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type cdylib --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 -C metadata=31d921365bf56f2f --out-dir /tmp/test_/target/wasm32-unknown-unknown/debug/deps --target wasm32-unknown-unknown -C incremental=/tmp/test_/target/wasm32-unknown-unknown/debug/incremental -L dependency=/tmp/test_/target/wasm32-unknown-unknown/debug/deps -L dependency=/tmp/test_/target/debug/deps --extern 'noprelude:alloc=/tmp/test_/target/wasm32-unknown-unknown/debug/deps/liballoc-72b348a1b400a2d6.rlib' --extern 'noprelude:compiler_builtins=/tmp/test_/target/wasm32-unknown-unknown/debug/deps/libcompiler_builtins-5f05eb2fe9129705.rlib' --extern 'noprelude:core=/tmp/test_/target/wasm32-unknown-unknown/debug/deps/libcore-7e733f1b75b6332e.rlib' --extern 'noprelude:panic_unwind=/tmp/test_/target/wasm32-unknown-unknown/debug/deps/libpanic_unwind-8d4d61c87153bded.rlib' --extern 'noprelude:proc_macro=/tmp/test_/target/wasm32-unknown-unknown/debug/deps/libproc_macro-e8cb90b4a1a8b576.rlib' --extern 'noprelude:std=/tmp/test_/target/wasm32-unknown-unknown/debug/deps/libstd-65633797cc840a5f.rlib' -Z unstable-options`

Manually running this command and adding

--extern 'noprelude:panic_abort=/tmp/test_/target/wasm32-unknown-unknown/debug/deps/libpanic_abort-fae018c7a2b94f26.rlib'

at the end makes it proceed

[dalcde]

The same bug is triggered when building an empty binary with -Z build-std and panic = "abort", without needing to cross-compile and/or use cdylib. The effect of cross-compiling to wasm32-unknown-unknown was simply to trigger panic = "abort". I have updated the issue title accordingly

[dalcde]

Closing as duplicate of #69090, rust-lang/wg-cargo-std-aware#29 . Fixed by setting -Z build-std=panic_abort,std