Questions about linking/examples

[ratmice]

I'm pretty new and ignorant of rust embedded development...

I was curious if there were any projects/example using it, I had seen the one in trouble But wasn't able to get it to compile due to what seemed like a circular dependency on embassy-time-driver perhaps caused by both apache-nimble crate and the trouble example depending on embassy-time? It wasn't clear to me what the issue was, it seemed to complain about two instances of the same version.

Trying to just take a minimal skeleton of an empty entry point I got a little bit further...

The first issue I had when linking, was duplicate symbols between libc and the libapache_nimble_sys.rlib file:
(snipped)

rust-lld: error: duplicate symbol: strlen
rust-lld: error: duplicate symbol: __assert_func

It's probably a bad idea but I was able to hack my way past that by telling the linker to allow multiple definitions of symbols :)

rustflags = [
    "-C", "link-arg=-Tlink.x",
    "-C", "link-arg=-Tdefmt.x",
    "-C", "link-arg=--allow-multiple-definition",
]

After that I ran into undefined references to all these functions that are commented out in embassy.rs:
port-layers/embassy.rs

Reading the comment there, I wasn't exactly sure what to look for in build.rs but related to the first error I saw, I noticed this comment:
which references: __assert_func which was one of the multiply defined functions I encountered earlier.

apache-nimble/build.rs

Anyhow, adding uncommented versions of those to my source files, It did finally link properly -- the following doesn't try and get anything actually functioning, but did get so far as to get it compiling linking. https://github.com/ratmice/apache_nimble_test/

I'm curious if these hacks are needed on others systems, or perhaps if there is some crate or step that I've missed. The version of newlib in my sysroot appears to be arm-none-eabi-newlib-4.4.0 if that helps.

Anyhow apologies for the wall of text, hopefully that covers everything I encountered/tried.

[akavel]

FWIW, I'm trying to see if I can use apache-nimble with trouble on nrf52840, and also just got to the duplicate symbol error for strlen and __assert_func. The current state of my attempt code is https://github.com/akavel/blergh1/tree/bb1578e2ea5ce4ff30f5d35765c0e6b52cbb0488 I copied the src/ nearly verbatim from two files:

• src/main.rs is a copy of https://github.com/embassy-rs/trouble/blob/trouble-host-v0.1.0/examples/apache-nimble/src/bin/ble_bas_peripheral.rs, with tiny tweaks to compile (commenting some stuff out etc.)
• src/ble_bas_peripheral.rs is a copy of https://github.com/embassy-rs/trouble/blob/trouble-host-v0.1.0/examples/apps/src/ble_bas_peripheral.rs, again with tiny tweaks to compile (mainly a few macros taken from the example's sibling fmt.rs file, to make info!() etc. calls be NOP).

I'm going to probably try and re-tread the subsequent steps of adding --allow-multiple-definition etc. (unless I get derailed by some other approach like trying to use https://github.com/jonas-schievink/rubble or something...)

EDIT: FWIW, I got the project to compile and upload. As is seemingly usual with embedded programming, that's only the first small part of the success, because after the upload, Stuff Seems Not Working™ (tried searching for new Bluetooth devices from my phone and don't seem to see anything relevant). Eh, surprise surprise, who would have guessed, still more patience, time, and debugging will be required 🤷‍♂️