[RP2040] Regression—blinky doesn't blink with latest microzig

[MatthiasPortzel]

Issue

I am no longer able to run programs on my Pico or RP2040 based board with current versions of Microzig. I've reproduced with the blinky example program included in this repo. A bisect points to #373 (5385b0e) as the first "bad" commit. I don't have more time to investigate this issue at present and so will continue using the last working version of microzig (520f370).

Reproduction

git clone https://github.com/ZigEmbeddedGroup/microzig.git
cd microzig
git switch --detach 5385b0e
cd examples/raspberrypi/rp2xxx
zig build

Drag zig-out/firmware/pico_blinky.uf2 onto a Pi Pico

Expected result: On-board LED flashes
Actual result: On-board LED does not turn on

Zig version: 0.13.0

Let me know if anyone is unable to reproduce with a Pico 1 and this example.

[MatthiasPortzel]

CC @marnix

[Grazfather]

I can reproduce, but not if I do zig build --release=fast. Does this also get around the issue?

[marnix]

@Grazfather To me it looks like your #394 is the correct fix for this.

Somehow Zig (0.13.0 and current 0.14-pre) requires an explicit .ARM.extab section in a .ld linker script, at least for thumb and/or ARM. But if one doesn't, the problem is only hit if code is actually generated for that section.

And my #373 (5385b0e) did trigger all MicroZig code to start using that section, at least in debug builds, and sometimes also even in --release=fast builds.

[MatthiasPortzel]

#394 does indeed fix this.

I also wanted to mention, with that PR merged into the zig-master branch, I’m able to run my program in current Zig 0.14-pre. 🎉