E0463 when running inside repo where embassy is a dependency

[eskorzon]

I am having a very similar issue as this closed issue. I can compile and run the example blinky on my board when cloning embassy-rs and doing cargo run --bin blinky --release from inside the cloned repo. When I add it through cargo in a fresh repo I get problems:

$ cargo run
   Compiling embassy-stm32 v0.0.0
   Compiling heapless v0.7.16
   Compiling cortex-m v0.7.7
error[E0463]: can't find crate for `std`
  |
  = note: the `thumbv7em-none-eabihf` target may not support the standard library
  = note: `std` is required by `embassy_stm32` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

For more information about this error, try `rustc --explain E0463`.
error: could not compile `embassy-stm32` (lib) due to previous error
warning: build failed, waiting for other jobs to finish...

Here is the output from cargo tree:

$ cargo tree
nucleo-32 v0.1.0 (/home/ekorzon/nucleo-32)
├── cortex-m v0.7.7
│   ├── bare-metal v0.2.5
│   │   [build-dependencies]
│   │   └── rustc_version v0.2.3
│   │       └── semver v0.9.0
│   │           └── semver-parser v0.7.0
│   ├── bitfield v0.13.2
│   ├── embedded-hal v0.2.7
│   │   ├── nb v0.1.3
│   │   │   └── nb v1.1.0
│   │   └── void v1.0.2
│   └── volatile-register v0.2.2
│       └── vcell v0.1.3
├── cortex-m-rt v0.7.3
│   └── cortex-m-rt-macros v0.7.0 (proc-macro)
│       ├── proc-macro2 v1.0.69
│       │   └── unicode-ident v1.0.12
│       ├── quote v1.0.33
│       │   └── proc-macro2 v1.0.69 (*)
│       └── syn v1.0.109
│           ├── proc-macro2 v1.0.69 (*)
│           ├── quote v1.0.33 (*)
│           └── unicode-ident v1.0.12
├── defmt v0.3.5
│   ├── bitflags v1.3.2
│   └── defmt-macros v0.3.6 (proc-macro)
│       ├── defmt-parser v0.3.3
│       │   └── thiserror v1.0.50
│       │       └── thiserror-impl v1.0.50 (proc-macro)
│       │           ├── proc-macro2 v1.0.69 (*)
│       │           ├── quote v1.0.33 (*)
│       │           └── syn v2.0.39
│       │               ├── proc-macro2 v1.0.69 (*)
│       │               ├── quote v1.0.33 (*)
│       │               └── unicode-ident v1.0.12
│       ├── proc-macro-error v1.0.4
│       │   ├── proc-macro-error-attr v1.0.4 (proc-macro)
│       │   │   ├── proc-macro2 v1.0.69 (*)
│       │   │   └── quote v1.0.33 (*)
│       │   │   [build-dependencies]
│       │   │   └── version_check v0.9.4
│       │   ├── proc-macro2 v1.0.69 (*)
│       │   ├── quote v1.0.33 (*)
│       │   └── syn v1.0.109 (*)
│       │   [build-dependencies]
│       │   └── version_check v0.9.4
│       ├── proc-macro2 v1.0.69 (*)
│       ├── quote v1.0.33 (*)
│       └── syn v2.0.39 (*)
├── defmt-rtt v0.4.0
│   ├── critical-section v1.1.2
│   └── defmt v0.3.5 (*)
├── embassy-executor v0.3.3
│   ├── critical-section v1.1.2
│   └── embassy-macros v0.2.1 (proc-macro)
│       ├── darling v0.20.3
│       │   ├── darling_core v0.20.3
│       │   │   ├── fnv v1.0.7
│       │   │   ├── ident_case v1.0.1
│       │   │   ├── proc-macro2 v1.0.69 (*)
│       │   │   ├── quote v1.0.33 (*)
│       │   │   ├── strsim v0.10.0
│       │   │   └── syn v2.0.39 (*)
│       │   └── darling_macro v0.20.3 (proc-macro)
│       │       ├── darling_core v0.20.3 (*)
│       │       ├── quote v1.0.33 (*)
│       │       └── syn v2.0.39 (*)
│       ├── proc-macro2 v1.0.69 (*)
│       ├── quote v1.0.33 (*)
│       └── syn v2.0.39 (*)
├── embassy-stm32 v0.0.0
├── embassy-time v0.1.5
│   ├── cfg-if v1.0.0
│   ├── critical-section v1.1.2
│   ├── embedded-hal v0.2.7 (*)
│   ├── futures-util v0.3.29
│   │   ├── futures-core v0.3.29
│   │   ├── futures-task v0.3.29
│   │   ├── pin-project-lite v0.2.13
│   │   └── pin-utils v0.1.0
│   └── heapless v0.7.16
│       ├── hash32 v0.2.1
│       │   └── byteorder v1.5.0
│       └── stable_deref_trait v1.2.0
│       [build-dependencies]
│       └── rustc_version v0.4.0
│           └── semver v1.0.20
└── panic-probe v0.3.1
    └── cortex-m v0.7.7 (*)

Here is my .cargo/config.toml:

[target.'cfg(all(target_arch = "arm", target_os = "none"))']
runner = "probe-run --chip STM32L432KCUx"

[build]
target = "thumbv7em-none-eabihf"

Here is my src/main.rs:

#![no_std]
#![no_main]
#![feature(type_alias_impl_trait)]

use defmt::*;
use embassy_executor::Spawner;
use embassy_stm32::gpio::{Level, Output, Speed};
use embassy_time::Timer;
use {defmt_rtt as _, panic_probe as _};

#[embassy_executor::task]
async fn blinker(mut led: Output<'static, PB3>, interval: Duration) {
    loop {
        led.set_high();
        Timer::after(interval).await;
        led.set_low();
        Timer::after(interval).await;
    }
}

#[embassy_executor::main]
async fn main(_spawner: Spawner) {
    let p = embassy_stm32::init(Default::default());
    info!("Hello World!");

    let led = Output::new(p.PB3, Level::High, Speed::Low);
    unwrap!(spawner.spawn(blinker(led, Duration::from_millis(300))));
}

Here is my Cargo.toml:

[package]
name = "nucleo-32"
version = "0.1.0"
edition = "2021"

[dependencies]
cortex-m = "0.7.7"
cortex-m-rt = "0.7.3"
defmt = "0.3.5"
defmt-rtt = "0.4.0"
embassy-executor = "0.3.3"
embassy-stm32 = "0.0.0"
embassy-time = "0.1.5"
panic-probe = "0.3.1"

Here is my memory.x:

MEMORY
{
  FLASH : ORIGIN = 0x08000000, LENGTH = 256K
  RAM : ORIGIN = 0x20000000, LENGTH = 64K
}

Here is my rust-toolchain.toml:

[toolchain]
channel = "nightly-2023-11-01"
components = [ "rust-src", "llvm-tools" ]
targets = [
    "thumbv7em-none-eabihf",
]

I am using a STM32L432KCU6 for what it's worth.

The same code works when compiled from inside a cloned repo, but not when done through a fresh repo where embassy is a dependency. Can embassy be used as a dependency or must it always be used as a clone of this repo? Am I missing some piece of this repo without which nothing will compile correctly? I'm seeing that embassy-stm32 is version 0.1.0 inside this repo, but the oldest version on crates.io is 0.0.0. Could that be a factor?

Originally posted by @eskorzon in https://github.com/embassy-rs/embassy/issues/917#issuecomment-1817352649

[eskorzon]

I think I fixed my immediate problem by using the git repo as the dependency source, rather than the crate.io. I would say this should be left open since embassy-rs is not able to be used very effectively as an external dependency via the package manager, and the real fix to the problem is publishing it correctly on the package manager.

Minimum functioning example of blinky with Nucleo-32 with STM32L432KCU6: https://github.com/eskorzon/nucleo-32-rs

[wouter-van-bastelaere]

I still have this same issue

[eskorzon]

This was some time ago for me, but have you tried using the GitHub url in your cargo.toml? ‘’’ embassy-executor = { version = "0.3.3", git = "https://github.com/embassy-rs/embassy", features = ["nightly", "arch-cortex-m", "executor-thread", "defmt", "integrated-timers"]} embassy-stm32 = { version = "0.1.0", git = "https://github.com/embassy-rs/embassy", features = ["nightly", "defmt", "unstable-pac", "stm32l432kc", "memory-x", "time-driver-any", "exti", "unstable-traits", "chrono"] } embassy-time = { version = "0.1.5", git = "https://github.com/embassy-rs/embassy", features = ["defmt", "defmt-timestamp-uptime", "tick-hz-32_768", "unstable-traits", "nightly"] } ‘’’

[lulf]

So, IMHO the best way to manage embassy dependencies is using Cargo.toml patches as recommended by the documentation. With that approach, there are these things you need to make sure is correct:

• The patch entry should point to a git revision using the rev field.
• The 'version' field for each embassy dependency in dependencies section must match the version in embassy repo for that git revision, otherwise it will not patch it correctly.
• Make sure you patch all embassy dependencies used in your app, otherwise you can get API incompatibilities.

[wouter-van-bastelaere]

eskorzon, lulf These do indeed both work. Thank you.