defmt-0.3.9 failed to build

[jonathanpallant]

Crate name

defmt

Build failure link

https://docs.rs/crate/defmt/0.3.9/builds/1566395

Additional details

I don't think we changed anything substantial since defmt-0.3.8, which built OK.

[syphar]

there wasn't any related change in docs.rs, though I can only imagine it's either related to your code, or perhaps that the new nightly version changed something.

[GuillaumeGomez]

Maybe -Zbuild-std is the one in fault here?

[syphar]

this is the diff: knurling-rs/defmt@defmt-v0.3.8...defmt-v0.3.9

[syphar]

ah, I remember there is also diff.rs: https://diff.rs/defmt/0.3.8/defmt/0.3.9/Cargo.toml

[jonathanpallant]

Do you use -Zbuild-std? Because I don't think we do. And yes, on thumbv6m-none-eabi for example, I'm pretty sure you have to say -Zbuild-std=core

➜  defmt git:(release-defmt-0.3.10) rustc +nightly --version
rustc 1.83.0-nightly (06bb8364a 2024-10-01)
➜  defmt git:(release-defmt-0.3.10) cargo +nightly build --target=thumbv6m-none-eabi
   Compiling bitflags v1.3.2
   Compiling defmt v0.3.9 (/Users/jonathan/Documents/knurling-rs/defmt/defmt)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.23s
➜  defmt git:(release-defmt-0.3.10) cargo +nightly build --target=thumbv6m-none-eabi -Zbuild-std
   Compiling gimli v0.29.0
error[E0432]: unresolved import `alloc::sync`
 --> /Users/jonathan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/gimli-0.29.0/src/read/dwarf.rs:2:12
  |
2 | use alloc::sync::Arc;
  |            ^^^^ could not find `sync` in `alloc`

error[E0432]: unresolved import `alloc::sync`
 --> /Users/jonathan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/gimli-0.29.0/src/read/abbrev.rs:4:12
  |
4 | use alloc::sync::Arc;
  |            ^^^^ could not find `sync` in `alloc`

For more information about this error, try `rustc --explain E0432`.
error: could not compile `gimli` (lib) due to 2 previous errors
➜  defmt git:(release-defmt-0.3.10) cargo +nightly build --target=thumbv6m-none-eabi -Zbuild-std=core
   Compiling bitflags v1.3.2
   Compiling defmt v0.3.9 (/Users/jonathan/Documents/knurling-rs/defmt/defmt)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.25s
➜  defmt git:(release-defmt-0.3.10)

[jonathanpallant]

The error message appears to come from here: https://github.com/rust-lang/cargo/blob/81e0670dddefc0b78b272e58decc0eea9def3720/src/cargo/core/compiler/standard_lib.rs#L80

[jonathanpallant]

Which was added last week: rust-lang/cargo@5e4a1db

[jonathanpallant]

Yup:

➜  defmt git:(release-defmt-0.3.10) RUSTC=~/Downloads/rust-nightly/rust-nightly-aarch64-apple-darwin/rustc/bin/rustc  ~/Downloads/rust-nightly/rust-nightly-aarch64-apple-darwin/cargo/bin/cargo build --target=thumbv6m-none-eabi -Zbuild-std
error: building std is not supported on the following targets: thumbv6m-none-eabi

➜  defmt git:(release-defmt-0.3.10) RUSTC=~/Downloads/rust-nightly/rust-nightly-aarch64-apple-darwin/rustc/bin/rustc  ~/Downloads/rust-nightly/rust-nightly-aarch64-apple-darwin/cargo/bin/cargo build --target=thumbv6m-none-eabi -Zbuild-std=core
error: "/Users/jonathan/Downloads/rust-nightly/rust-nightly-aarch64-apple-darwin/rustc/lib/rustlib/src/rust/library/Cargo.lock" does not exist, unable to build with the standard library, try:
        rustup component add rust-src

No idea how to add rust-src to a tarball installation, but that's the error.

[jonathanpallant]

I sent https://crates.io/crates/thejpster-test-docs-target down the line, which is an inoffensive test crate. If you can't build it then I'm pretty sure it's a docs.rs but and not a defmt bug.

[syphar]

Maybe -Zbuild-std is the one in fault here?

@GuillaumeGomez you mean we need add it do the docs.rs metadata to use #2107 ?

I sent https://crates.io/crates/thejpster-test-docs-target down the line, which is an inoffensive test crate. If you can't build it then I'm pretty sure it's a docs.rs but and not a defmt bug.

there was no docs.rs change that might cause this, so I imagine the nighty version changes you linked could cause the error.

If you have a test crate that errors too (and IMO it likely will with the targets) we might try it with cargo-args=["-Zbuild-std"]

[GuillaumeGomez]

It's not clear when it's needed. Also, I'm surprised it worked without using -Zbuild-std (I thought we used it but we don't).

[jonathanpallant]

AFAIK will need -Zbuild-std=core when building for a target that doesn't have libstd. I guess most of your crates build for the host machine, but the docs.rs metadata for this one forces you to build it for thumbv6m-none-eabi and thumbv7em-none-eabihf, because it's known to not work on Windows/macOS/Linux.

[jonathanpallant]

https://crates.io/crates/thejpster-test-docs-target is perpetually stuck at the back of the queue, perhaps because you've rated as a crate of low value (it is, it's terrible).

[syphar]

https://crates.io/crates/thejpster-test-docs-target is perpetually stuck at the back of the queue, perhaps because you've rated as a crate of low value (it is, it's terrible).

it's not deprioritized, so has the same prio as normal releases (deprioritized is shown in braces after the crate, if we do it, like (priority: -1))

[jonathanpallant]

So why is everything else being added to the queue in front of it? It was one-from-last and 27th and is now one-from-last and 63rd.

[syphar]

I can't Check the logs right now, my guess is build-attempts.

For a certain type of build errors ( like the one from the original crate) we actually try the build up to 5 times with a delay in between.

[jonathanpallant]

Ah, it did build but it went back in the queue!!

and it failed: https://docs.rs/crate/thejpster-test-docs-target/0.1.0/builds/1567394

error: building std is not supported on the following targets: thumbv7em-none-eabihf, thumbv6m-none-eabi

So yup, not defmt's fault.

[syphar]

so, I don't know enough about the build process around these targets to be able to judge where the problem lies, in the cargo change, in how docs.rs builds docs, of if we're missing a build arg (build-std?) and we were just lucky until now.

What I know is that before the mentioned cargo change, the doc build works.

So I froze the nightly version docs.rs uses to nightly-2024-11-21. A rebuild for thejpster-test-docs-target then succeeds, so did the rebuild for defmt 0.3.9.

[syphar]

I want to create a bug-report for cargo, @jonathanpallant could you push the test crate to github so I can include it?

[syphar]

I wonder if cargo-args = ["-Zbuild-std=core"] in the metadata might help...

[syphar]

I started with a zulip thread

[jonathanpallant]

https://github.com/jonathanpallant/thejpster-test-docs-target

[syphar]

the final fix is still in progress, but since there were some other releases that needed a newer version I un-froze the nightly version.

Feel free to ping me if you need to build another release, and we can handle it together. It might also be worth trying to add Zbuild-std=core as done here

[syphar]

coming from the zulip discussion I would say this is fixed now.

Feel free to reopen if it breaks again, if it fails please first try adding -Zbuild-std=core or -Zbuild-std to the docs.rs metadata