`error: package ID specification `panic_unwind` did not match any packages` with `-Zbuild-std`

[Wyvern]

Update to latest rust nightly: cargo 1.85.0-nightly (769f622e1 2024-12-14) got error: package ID specification panic_unwind did not match any packages when build with -Zbuild-std option.

It happened only on today's update, all builds before have no problems.

What does it mean? And how to fix it...

[weihanglo]

Could you share a minimal reproducible example, with the complete error mesaage? Like the content of your .cargo/config.toml, crates and features specified in -Zbuild-std and -Zbuild-std-feature, env var like RUSTFLAGS, and the target platform you're building.

It might be related to #14899, which automatically determine building core or std, if -Zbuild-std has no crate specified.

[Wyvern]

Could you share a minimal reproducible example, with the complete error mesaage?

This is the complete error mesaage, the only output content before actually start building.

Like the content of your .cargo/config.toml, crates and features specified in -Zbuild-std and -Zbuild-std-feature

-Zbuild-std=std,proc_macro,panic_abort -Zbuild-std-features=panic_immediate_abort"

[Wyvern]

It might be related to #14899, which automatically determine building core or std, if -Zbuild-std has no crate specified.

I try to remove -Zbuild-std-features=panic_immediate_abort and build succeeded. NOT sure it related to #14899.

[weihanglo]

This failed because since 125e873
std_resolve only includes sysroot as primary package.
When any custom Cargo feature is provied through -Zbuild-std-feature,
the default feature set panic-unwind wouldn't be gone, so
no panic_unwind crate presents in std_resolve.

When then calling std_resolve.query with the default set of
crates from std_crates, which automatically includes
panic_unwind when std presents, it'll result in spec not found
because panic_unwind was not in std_resolve anyway.

[Wyvern]

So -Zbuild-std-feature=panic-unwind,other-features... will be necessary from now on?

[weihanglo]

I would recommend using an older nightly toolchain for now, if it is urgent. rustup toolchain install nightly-2024-12-13 should work.

[Manishearth]

A simple reproduction for this is cargo +nightly rustc -Z build-std=std,panic_abort -Zbuild-std-features=panic_immediate_abort on an empty cargo new --lib foo crate.

I was able to cargo bisect-rustc it down to rust-lang/rust#134278

@weihanglo can that commit be reverted?