esp-backtrace does not print backtrace in certain situations.

[t-moe]

I wanted to use esp_backtrace::arch::backtrace() to obtain a backtrace in my watchdog interrupt handler, so that I can print a backtrace of where the watchdog occurred. To my surprise the backtrace was empty (even though I have force-frame-pointers enabled).

Apparently the issue was that some stack-frames around the interrupt handling code where not 16-byte aligned, which would cause the printing to be aborted (due to esp_backtrace::is_valid_ram_addr returning false).

https://github.com/esp-rs/esp-hal/blob/e033162ffd1994c46c478de2de5ec1eed3869762/esp-backtrace/src/lib.rs#L214C1-L217C6

When I removed the 16-byte alignment check, I got a correct backtrace back until main.

I'm not sure if there are also other situations where the stackframes are not 16-byte aligned, or whether that's just because I'm inside an interrupt handler. I just wanted to share my discovery, not sure if its of any help to you.

Thank you

[bjoernQ]

Thanks - that's an interesting observation and getting a backtrace is especially useful for WDT interrupts (probably not for other interrupts)