Issue using async_trait with zigbuild for x86_64-unknown-linux-gnu

[nmoutschen]

Hi! 👋 First of all, thanks a lot for this awesome project!

I'm trying to use cargo zigbuild with this project that uses the async_trait crate from Ubuntu on x86_64.

When I use cargo zigbuild --target aarch64-unknown-linux-gnu, it works without any error. Same with cargo build --target x86_64-unknown-linux-gnu.
However, when I run cargo zigbuild --target x86_64-unknown-linux-gnu, I get a pretty lengthy error about async functions not supported in traits, and that thiserror cannot allocate memory in static TLS block.

Error trace from compilation:

error[E0706]: functions in traits cannot be declared `async`
  --> src/event_bus/eventbridge/mod.rs:32:5
   |
32 |     #[instrument(skip(self))]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
33 |     async fn send_event(&self, event: &Self::E) -> Result<(), Error> {
   |     ----- `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
   = note: this error originates in the attribute macro `instrument` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0706]: functions in traits cannot be declared `async`
  --> src/event_bus/eventbridge/mod.rs:45:5
   |
45 |     #[instrument(skip(self, events))]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
46 |     async fn send_events(&self, events: &[Self::E]) -> Result<(), Error> {
   |     ----- `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
   = note: this error originates in the attribute macro `instrument` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0706]: functions in traits cannot be declared `async`
  --> src/event_bus/void.rs:18:5
   |
18 |       async fn send_event(&self, _: &Self::E) -> Result<(), Error> {
   |       ^----
   |       |
   |  _____`async` because of this
   | |
19 | |         Err(Error::InternalError("send_event is not supported"))
20 | |     }
   | |_____^
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/event_bus/void.rs:22:5
   |
22 |       async fn send_events(&self, _: &[Self::E]) -> Result<(), Error> {
   |       ^----
   |       |
   |  _____`async` because of this
   | |
23 | |         Err(Error::InternalError("send_events is not supported"))
24 | |     }
   | |_____^
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/event_bus/mod.rs:14:5
   |
14 |     async fn send_event(&self, event: &Self::E) -> Result<(), Error>;
   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |     |
   |     `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/event_bus/mod.rs:15:5
   |
15 |     async fn send_events(&self, events: &[Self::E]) -> Result<(), Error>;
   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |     |
   |     `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/dynamodb/mod.rs:32:5
   |
32 |     #[instrument(skip(self))]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
33 |     async fn all(&self, next: Option<&str>) -> Result<ProductRange, Error> {
   |     ----- `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
   = note: this error originates in the attribute macro `instrument` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/dynamodb/mod.rs:60:5
   |
60 |     #[instrument(skip(self))]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
61 |     async fn get(&self, id: &str) -> Result<Option<Product>, Error> {
   |     ----- `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
   = note: this error originates in the attribute macro `instrument` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/dynamodb/mod.rs:81:5
   |
81 |     #[instrument(skip(self))]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
82 |     async fn put(&self, product: &Product) -> Result<(), Error> {
   |     ----- `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
   = note: this error originates in the attribute macro `instrument` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/dynamodb/mod.rs:98:5
   |
98 |     #[instrument(skip(self))]
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
99 |     async fn delete(&self, id: &str) -> Result<(), Error> {
   |     ----- `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
   = note: this error originates in the attribute macro `instrument` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/memory.rs:28:5
   |
28 |       async fn all(&self, _: Option<&str>) -> Result<ProductRange, Error> {
   |       ^----
   |       |
   |  _____`async` because of this
   | |
29 | |         Ok(ProductRange {
30 | |             products: self
31 | |                 .data
...  |
38 | |         })
39 | |     }
   | |_____^
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/memory.rs:44:5
   |
44 |       async fn get(&self, id: &str) -> Result<Option<Product>, Error> {
   |       ^----
   |       |
   |  _____`async` because of this
   | |
45 | |         Ok(self.data.read().unwrap().get(id).cloned())
46 | |     }
   | |_____^
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/memory.rs:51:5
   |
51 |       async fn put(&self, product: &Product) -> Result<(), Error> {
   |       ^----
   |       |
   |  _____`async` because of this
   | |
52 | |         self.data
53 | |             .write()
54 | |             .unwrap()
55 | |             .insert(product.id.clone(), product.clone());
56 | |         Ok(())
57 | |     }
   | |_____^
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/memory.rs:62:5
   |
62 |       async fn delete(&self, id: &str) -> Result<(), Error> {
   |       ^----
   |       |
   |  _____`async` because of this
   | |
63 | |         self.data.write().unwrap().remove(id);
64 | |         Ok(())
65 | |     }
   | |_____^
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/mod.rs:22:5
   |
22 |     async fn all(&self, next: Option<&str>) -> Result<ProductRange, Error>;
   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |     |
   |     `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/mod.rs:28:5
   |
28 |     async fn get(&self, id: &str) -> Result<Option<Product>, Error>;
   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |     |
   |     `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/mod.rs:34:5
   |
34 |     async fn put(&self, product: &Product) -> Result<(), Error>;
   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |     |
   |     `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error[E0706]: functions in traits cannot be declared `async`
  --> src/store/mod.rs:40:5
   |
40 |     async fn delete(&self, id: &str) -> Result<(), Error>;
   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |     |
   |     `async` because of this
   |
   = note: `async` trait functions are not currently supported
   = note: consider using the `async-trait` crate: https://crates.io/crates/async-trait

error: /home/CENSORED/projects/serverless-rust-demo/target/debug/deps/libthiserror_impl-83b2547aa6b39328.so: cannot allocate memory in static TLS block
 --> src/event_bus/eventbridge/ext.rs:2:5
  |
2 | use aws_sdk_eventbridge::model::PutEventsRequestEntry;
  |     ^^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0706`.
error: could not compile `products` due to 19 previous errors
warning: build failed, waiting for other jobs to finish...
error: build failed

For reference, here is one of the traits that cargo zigbuild complains about:

#[async_trait]
pub trait EventBus {
    type E;

    async fn send_event(&self, event: &Self::E) -> Result<(), Error>;
    async fn send_events(&self, events: &[Self::E]) -> Result<(), Error>;
}

[messense]

I can reproduce this issue on Ubuntu 20.04, but it seems to work fine on macOS.

[messense]

So this issue is caused by Cargo using the same linker when --target is the same as the host target, for more information see rust-lang/cargo#3349 and there is already an unstable option target-applies-to-host to fix it. But you need to use the nightly Rust compiler because that feature is unstable.

First create the .cargo/config.toml file and add target-applies-to-host = false to its content, then run cargo zigbuild with the unstable option enabled:

cargo +nightly zigbuild --target x86_64-unknown-linux-gnu -Ztarget-applies-to-host

[messense]

With commit 407e2e4, if you don't specify a glibc version it'll skip setting up zig as linker and just use system linker instead when the cross target is exactly the same as the host target. That should avoid having to use the target-applies-to-host option most of the time.

[messense]

With #9 which is released in v0.5.2, the only workaround is switching to nightly Rust, cargo-zigbuild will take care of enabling the target-applies-to-host option automatically.