Build failure

[fdubois1]

We have a dependency on serde 1.0 so we moved to 1.0.95 and now, we have this issue in our build for Android (It builds for other platforms) :

  error[E0432]: unresolved imports `std::sync::atomic::AtomicI64`, `std::sync::atomic::AtomicU64`
     --> /home/user/.cargo/registry/src/github.com-1ecc6299db9ec823/serde-1.0.95/src/lib.rs:221:33
  
  221 |     pub use std::sync::atomic::{AtomicI64, AtomicU64};
                                   ^^^^^^^^^  ^^^^^^^^^ no `AtomicU64` in `sync::atomic`
                                   |
                                   no `AtomicI64` in `sync::atomic`
  help: a similar name exists in the module
  
  221 |     pub use std::sync::atomic::{AtomicI8, AtomicU64};
                                   ^^^^^^^^
  help: a similar name exists in the module
  
  221 |     pub use std::sync::atomic::{AtomicI64, AtomicU8};
                                              ^^^^^^^^
  
  error: aborting due to previous error

I thought I had an old version of rust, but I'm using 1.35.0 so I don't understand why AtomicI64 is not found. Any hint ? Thanks for your help

[tymcauley]

I just ran into this exact same issue. It appears this is new in 1.0.95 (I can't reproduce it in 1.0.94). I've only noticed this issue for the mips-unknown-linux-gnu and mips-unknown-linux-musl targets (works fine on x86_64 targets). You can reproduce this by creating the serde test crate from this repo's homepage (the simple JSON serde example), and running these commands:

rustup target add mips-unknown-linux-gnu
rustup target add mips-unknown-linux-musl
cargo build --target mips-unknown-linux-gnu
cargo build --target mips-unknown-linux-musl

Both of those cargo build commands should fail with the same signature mentioned above, while a vanilla cargo build for an x86_64 target will succeed.

[fdubois1]

In my case, I didn't specify the exact target, but it is --target arm-linux-androideabi

[Roguelazer]

Hm. The documentation does include the following line:

MIPS and PowerPC do not support AtomicU64, and "more esoteric" platforms like armv5te, thumv6m, etc, have little-to-no support.

It looks like the relevant cfg flag never got merged (rust-lang/rust#56753).

For now, do y'all want to just gate this feature on x86/x86_64 in the build.rs script so we stop breaking MIPS and ARM?

[fdubois1]

Thank you for your answer. Yeah, I think it make sense to gate the feature to stop breaking the build with some target. It is better to remove the feature than getting a build error I think...

[Roguelazer]

okay I'll send over a PR in a minute

[dtolnay]

Sorry about the breakage! I've yanked serde 1.0.95, so cargo should start giving you 1.0.94 which doesn't have those impls.

Ideally we would use #[cfg(target_has_atomic = "64")] but it isn't stable yet. We can try to do a whitelist of platforms that are known to have AtomicU64 instead.

[fdubois1]

Thank you, it works and use version 1.0.94.