build_std can't find crate for panic_abort

[Timmmm]

I'm trying to build std for wasm32-unknown-unknown. I cloned the wasm template but compiling it gives this:

$ cargo +nightly build -Z build-std --target wasm32-unknown-unknown
...
   Compiling wasm-pack-template v0.1.0 (/Users/tim/wasm-pack-template)
error[E0463]: can't find crate for `panic_abort`

I tried adding the panic_abort crate from crates.io but it gives some other errors and I'm pretty sure I shouldn't have to.

Compiling with RUSTC_LOG=info gives a bit more info:

INFO rustc_metadata::creader panic runtime not found -- loading panic_abort
INFO rustc_metadata::creader resolving crate `panic_abort`
INFO rustc_metadata::creader falling back to a load
INFO rustc_metadata::locator lib candidate: /Users/tim/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib/libpanic_abort-14c6721c1e3ddac4.rlib
INFO rustc_metadata::locator rlib reading metadata from: /Users/tim/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib/libpanic_abort-14c6721c1e3ddac4.rlib
INFO rustc_metadata::locator Rejecting via proc macro: expected true got false
INFO rustc_metadata::locator metadata mismatch

As you can see it is looking for the wrong libpanic_abort.rlib! It's especially weird because it finds the right crate when it tries to resolve other ones, e.g:

INFO rustc_metadata::creader resolving crate `cfg_if`
INFO rustc_metadata::creader falling back to a load
INFO rustc_metadata::locator lib candidate: /Users/tim/wasm-pack-template/target/wasm32-unknown-unknown/debug/deps/libcfg_if-40fde05178aa587c.rlib
INFO rustc_metadata::locator lib candidate: /Users/tim/wasm-pack-template/target/wasm32-unknown-unknown/debug/deps/libcfg_if-40fde05178aa587c.rmeta
INFO rustc_metadata::locator rmeta reading metadata from: /Users/tim/wasm-pack-template/target/wasm32-unknown-unknown/debug/deps/libcfg_if-40fde05178aa587c.rmeta
INFO rustc_metadata::creader register crate `cfg_if` (cnum = 17. private_dep = false)

And it actually did successfully compile libpanic_abort.rlib for wasm:

$ ls -1 target/wasm32-unknown-unknown/debug/deps/*panic*
target/wasm32-unknown-unknown/debug/deps/console_error_panic_hook-837ce2b56de85633.d
target/wasm32-unknown-unknown/debug/deps/libconsole_error_panic_hook-837ce2b56de85633.rlib
target/wasm32-unknown-unknown/debug/deps/libconsole_error_panic_hook-837ce2b56de85633.rmeta
target/wasm32-unknown-unknown/debug/deps/libpanic_abort-5dadd1d612661286.rlib
target/wasm32-unknown-unknown/debug/deps/libpanic_abort-5dadd1d612661286.rmeta
target/wasm32-unknown-unknown/debug/deps/libpanic_unwind-e15a40c08ac4e7e5.rlib
target/wasm32-unknown-unknown/debug/deps/libpanic_unwind-e15a40c08ac4e7e5.rmeta
target/wasm32-unknown-unknown/debug/deps/panic_abort-5dadd1d612661286.d
target/wasm32-unknown-unknown/debug/deps/panic_unwind-e15a40c08ac4e7e5.d

Possibly related to #56228. I also made a thread about this here.

[ehuss]

This is a known issue (unfortunately), mainly tracked in rust-lang/wg-cargo-std-aware#29. The build-std feature doesn't know how to handle abort vs unwind targets, so it doesn't handle them automatically. wasm doesn't support unwinding, so it needs to use abort. You can force it by using -Zbuild-std=std,panic_abort.

[Timmmm]

Aha, that worked perfectly, thanks! Are the options for build-std documented anywhere? I guess I'll close this since it is tracked elsewhere.

[ehuss]

build-std documentation is at https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#build-std

[TopDev1007]

I try all the feedback but it doesn't work successfully.

[Timmmm]

What error did you get? Coincidentally I did a talk about this yesterday and it still works for me.