[11-usart] Cannot compile in release mode

[Petrus97]

The issue

Hi all, I tried to compile in release mode but I got this error:

warning: Linking globals named 'CORE_PERIPHERALS': symbol multiply defined!

error: failed to load bc of "cortex_m-b26f2bd747183185.cortex_m.87incrm8-cgu.0.rcgu.o": 

error: aborting due to previous error; 3 warnings emitted

error: could not compile `usart`

What I found

Searching on the web the reason is that during the compilation there are multiple versions of cortex-m libraries. Running cargo tree here is what i found

[11-usart]$ cargo tree | grep cortex-m
│   ├── cortex-m v0.5.6
│   ├── cortex-m-rt v0.6.13
│   │   ├── cortex-m-rt-macros v0.1.8 (proc-macro)
│   │       ├── cortex-m v0.5.6 (*)
│   │       │   ├── cortex-m v0.5.6 (*)
│   │       │   ├── cortex-m-rt v0.6.13 (*)
│       └── cortex-m v0.7.2

As you can see I have two different version of cortex-m libs, this lib is used from panic-itm lib.

└── panic-itm v0.4.2
│       └── cortex-m v0.7.2
│           ├── bare-metal v0.2.5 (*)
│           ├── bitfield v0.13.2
│           ├── embedded-hal v0.2.5 (*)
│           └── volatile-register v0.2.0 (*)

Searching in the project folder in Cargo.toml of auxiliary lib I found these dependencies

[dependencies]
cortex-m = "=0.5.6" # 0.5.11 introduces a breaking change.  Use 0.5.6, since we know it works for this example
cortex-m-rt = "0.6.3"
panic-itm = "0.4.0"

The package version of panic-itm is 0.4.0 but during compilation I got 0.4.2

   ...
   Compiling panic-itm v0.4.2
   ...

Looking at panic-itm v0.4.2 source the Cargo.toml file we have

[dependencies.cortex-m]
version = ">= 0.5.8, < 0.8"

In fact, v0.4.0 need the v0.5.6 cortex-m, but cargo doesn't downloaded it. I tried manually but I got

[11-usart]$ cargo install panic-itm --version 0.4.0
    Updating crates.io index
error: specified package `panic-itm v0.4.0` has no binaries

Just a question

Why when I compile in debug-mode it compiles fine? Does it compiles and put both v0.5.6 and v.0.7.2 cortex-m lib in the binary?

[eisnstein]

I changed every Cargo.toml file, where the panic-itm dependency is defined to panic-itm = "=0.4.0". That is in: 05, 06, 07, 08, 09, 11, 14, 15, 16. After that, I could compile 11-usart in release mode. I have not checked, if the others still work.

[Petrus97]

Hi @eisnstein, thank you for the fix (sorry for the late answer). Now I can compile the 11-usart in release mode (I changed only the 05, 06 and 07) but changing the others Cargo.toml break the release mode compilation on them (In every chapter folder there is a different cortex-m version... 😐). For me it's not a big problem, now I'm curious about what happen during release mode compilation respect to debug mode. Before closing the issue can you indicate me some resources that explain this behaviour and why we need to modify the Cargo.toml in that way? Thank you in advance!

[eisnstein]

No sorry I can't help you, I just tried to "fix" the panic-itm to version 0.4.0 with the "=", so that it does not update to a newer version. I am completely new to Rust and don't know how all this works.

[sirhcel]

Hi @Petrus97, several changes and fixes have landed in this repository recently (for example https://github.com/rust-embedded/discovery/pull/341). They include switching to the actively maintained stm32f3xx-hal.

As of https://github.com/rust-embedded/discovery/commit/cc254bbbb381931e22e5f491ad48e558cc5f940d I can build all examples successfully even in release mode.

$ git describe --always --dirty
cc254b
$ rustc --version
rustc 1.52.1 (9bc8c42bb 2021-05-09)
$ cargo build --release --target thumbv7em-none-eabihf 

Yes, there are still warnings about unused variables, constants, ... But the build itself works.

I expect this to resolve your issues too. Does the latest updates work out for you too?