Undefined reference to abort

[ssnover]

I've been trying to get a minimal example building and have hit a wall trying to get the final project to link together.

Full project repo is here

But I'm compiling with recently nightly, have pulled in avr-std-stub in Cargo.toml and in main.rs have extern crate avr_std_stub;. Finally, I've specified in my .cargo/config.toml to build libraries and set my target:

[build]
target = "avr-unknown-gnu-atmega328"

[unstable]
build-std = ["core", "compiler_builtins"]

However, despite all this, I'm getting errors on build with cargo +nightly build --release:

ssnover:arduino-blink$ cargo +nightly build --release
   Compiling arduino-blink v0.1.0 (/home/ssnover/dev/arduino-blink)
WARN rustc_codegen_ssa::back::link Linker does not support -no-pie command line option. Retrying without.
error: linking with `avr-gcc` failed: exit status: 1
  |
  = note: "avr-gcc" "-mmcu=atmega328" "/home/ssnover/dev/arduino-blink/target/avr-unknown-gnu-atmega328/release/deps/arduino_blink-7b03611be97ed54b.arduino_blink.7cb9b83c-cgu.0.rcgu.o" "-Wl,--as-needed" "-L" "/home/ssnover/dev/arduino-blink/target/avr-unknown-gnu-atmega328/release/deps" "-L" "/home/ssnover/dev/arduino-blink/target/release/deps" "-L" "/home/ssnover/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/avr-unknown-gnu-atmega328/lib" "-Wl,--start-group" "-Wl,--end-group" "-Wl,-Bstatic" "/home/ssnover/dev/arduino-blink/target/avr-unknown-gnu-atmega328/release/deps/libcompiler_builtins-4be1e100b4795ac1.rlib" "-Wl,-Bdynamic" "-lgcc" "-Wl,-znoexecstack" "-L" "/home/ssnover/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/avr-unknown-gnu-atmega328/lib" "-o" "/home/ssnover/dev/arduino-blink/target/avr-unknown-gnu-atmega328/release/deps/arduino_blink-7b03611be97ed54b.elf" "-Wl,--gc-sections" "-Wl,-O1" "-nodefaultlibs"
  = note: /home/ssnover/dev/arduino-blink/target/avr-unknown-gnu-atmega328/release/deps/arduino_blink-7b03611be97ed54b.arduino_blink.7cb9b83c-cgu.0.rcgu.o: In function `main':
          arduino_blink.7cb9b83c-cgu.0:(.text.main+0x4): undefined reference to `abort'
          /home/ssnover/dev/arduino-blink/target/avr-unknown-gnu-atmega328/release/deps/arduino_blink-7b03611be97ed54b.arduino_blink.7cb9b83c-cgu.0.rcgu.o: In function `arduino_blink::__avr_device_rt_main::hcc00f93d7920e3e3':
          arduino_blink.7cb9b83c-cgu.0:(.text._ZN13arduino_blink20__avr_device_rt_main17hcc00f93d7920e3e3E+0x9c): undefined reference to `abort'
          /home/ssnover/dev/arduino-blink/target/avr-unknown-gnu-atmega328/release/deps/arduino_blink-7b03611be97ed54b.arduino_blink.7cb9b83c-cgu.0.rcgu.o: In function `core::panicking::panic::h3bd82c06970c382b':
          arduino_blink.7cb9b83c-cgu.0:(.text.unlikely._ZN4core9panicking5panic17h3bd82c06970c382bE+0x4): undefined reference to `abort'
          collect2: error: ld returned 1 exit status
          
  = help: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
  = note: use the `-l` flag to specify native libraries to link
  = note: use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)

error: could not compile `arduino-blink` due to previous error

Is abort something that needs to be defined in my project since it's not being provided by libcore or is this supposed to be similar to eh_personality where there's a crate that's necessary to make the ecosystem work?

[Rahix]

Hi, what exactly are you trying to do? Are you just interested in getting Rust on AVR running? Then please check out the guide in the README of this project: Quickstart. It links you to a project template that has everything set up correctly already.

If you are specifically trying to get avr-std-stub working, maybe you need to tell me more about the reasons...

---

That out of the way, a few technical comments about your question. You can ignore them if you are just starting out...

• avr-std-stub is not needed on new rustc versions. The panic handler can either be pulled in from one of the existing implementations like panic-halt or any of the other panic-* crates. Or you can define it yourself with custom behavior as seen in this avr-hal example: uno-panic.rs
• eh_personality is about unwinding. On AVR you probably shouldn't do unwinding panics. You can switch to aborting panics by setting panic = "abort" in your cargo profile. After doing that, the lang item eh_personality is also not needed anymore.
• abort() is usually defined by the runtime. In the case of AVR, that is avr-libc. Right now, we are still depending on avr-libc for such runtime features but this will eventually change (see Get rid of avr-libc dependency avr-device#76)
• Finally, I see you're explicitly mentioning compiler-builtins in your build-std config. I've never seen that being required, was there a reason why you added it?

[ssnover]

Admittedly some of the changes I made to how the crate was building was trial and error based on error messages I was getting and experience I've had previously with getting msp430 and cortex-m projects to build in Rust. This version was the farthest I got, but some of it may be is now hindering the correct solution.

I'll scan the template in the quickstart for differences and get back to you. I was using the avr-rust book to get a basic project started and I think a fair bit of it is currently out-of-date based on my experimentation and some of your technical comments above.

[ssnover]

Relative to what I had before I've now swapped avr-std-stub for panic-halt, added panic = "abort" to my build profile, and removed compiler-builtins. I'm still getting a linking error on abort which implies to me that avr-libc's not being found during linking.

I've got the correct archive file at /usr/lib/avr/lib/avrxmega3/libc.a. But don't see it in my linker invocation to avr-gcc that's being printed (just -lgcc so maybe that's supposed to be linking libc?).

[ssnover]

Alright, the final unlock that I admittedly don't quite understand is pulling the target spec file from the avr-hal-template repo. It seems like the built-in target avr-unknown-gnu-atmega328 doesn't correctly link avr-libc which is an unfortunate footgun. Meanwhile the one called out in the spec avr-unknown-unknown I guess properly finds it.

[ssnover]

My compiler version was cargo 1.65.0-nightly (4ed54cecc 2022-08-27) for anyone who might be following along later.