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rust-embedded / discovery

Discover the world of microcontrollers through Rust!
https://docs.rust-embedded.org/discovery/
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[5.3] Different available breakpoints (dev build) compared to book #531

Open PieterJanVdb opened 1 year ago

PieterJanVdb commented 1 year ago

Not entirely sure what is happening here, I'm guessing it's some compiler optimization, but I can't seem to put a breakpoint on line 13 as shown in the chapter. Instead it only allows me to break on line 12 and line 16 (the loop).

The asm TUI looks like this:

afbeelding

While the disassembly looks like this:

afbeelding

At first glance it seems like the statement on line 13 has been optimized away, but I'm pretty sure the binary was built without optimizations:

afbeelding

For the record, I'm running this on Mac M1, with arm-none-eabi-gdb as the debugger

CarlosLaraFP commented 1 year ago

Having this same issue on iMac.

kazauwa commented 1 year ago

Same issue here on M1 Mac. The lines in the range 13-15 seem to be absent, you can verify this by executing next several times. You will see that gdb jumps from line 12 straight to line 16. Also, I tried disabling optimizations explicitly by specifying "-C", "opt-level=0" in .cargo/config, but it didn't help.

kazauwa commented 1 year ago

I got it to work by downgrading rust to 1.66 and half crate to 2.2.1 (since 2.3.1 requires rust 1.70+). It seems that there was a change in 1.69 that is causing this weird optimization because 1.68.2 was the last version where I couldn't reproduce it. I wonder if this is the case for other platforms.

UPD. This also happens on Linux x86_64

fosskers commented 1 year ago

This is also currently happening on Arch Linux for me. For now I'll move forward with the chapter and "take his word for it".

fosskers commented 1 year ago

Immediate discoveries: the lines in question aren't actually being compiled away. By manually nexting, while it does jump over the _y = x, doing a info locals afterwards does show that _y = 42, so the setting did indeed happen.

Berty48237 commented 1 year ago

I have the same issue on Linux Mint 20.04, Ubuntu 20.04. I.e. jumping from line 12 to 15 whilst single stepping. I also have another problem with the code on section 5.4 'The led and delay abstractions'. When using 'next' to step over the call to let (mut delay, mut leds): (Delay, LedArray) = aux5::init() it jumps straight to the loop, as if I'd typed 'continue'. When using the assembler view and 'si' to step into the aux5::init() function, it again steps over it. Anyone else experiencing this?