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Comment by vlovich123 | Hacker News Reader

> because debugger breaks hardware

What? Seems like you’re talking about embedded but I’ve done a lot of embedded projects in my time and I’ve never had a debugger that breaks the HW.

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On embedded, debuggers almost never work until you get to really expensive ones.

In addition, debuggers tend to obscure the failure because they turn on all the hardware which tends to make bugs go away if they are related to power modes.

One of my "best" debuggers for embedded was putting an interactive interpreter over a serial interface on an interrupt so I could query the state of things when a device woke up even if it was hung--effectively a run time injectable "printf".

Crude, but it could trace down obscure bugs that were rare because the device would stay in the failure mode.

The bigeest problem was maintaining the database of code so that we knew exactly what build was on a device. We had to hash and track the universe.

I’ve worked with many M3s and M4s and some Cypress microchips and the JTAG debuggers always worked fine as far as I recall. There were some vendors that liked to force you to buy really expensive ancillary HW but a) there was plenty of OSS that worked fairly well b) you could pick which vendor you went with.

All of those chips you mentioned will turn on all the units at full power when you connect a debugger to them.

And the OSS stuff never works correctly. I wind up debugging the OSS stuff more than my own hardware. And I've used a LOT of OSS (to the point that I wrote software to use a Beaglebone as my SWD debugger to work around all the idiocies--both commercial and OSS).

Depends what you're working on. Stopped in an unfortunate place? That one element didn't get turned off and burned out. Or the motor didn't stop. Or the crucial interrupts got missed and your state is now reset. Or...

are there debugging tools specifically for situations like that? do you just write code to test manually? How do you ensure dev builds don't break stuff like that even without considering debugging?

The most useful tool is a full tracing system (basically a stream of run instructions you can use to trace the execution of the code without interrupting it), but unfortunately they're quite expensive and proprietery, and require extra connections to the systems that do support them, so they're not particularly commonly used. Most people just use some kind of home-grown logging/tracing system that tracks the particular state they're interested in, possibly logged into a ringbuffer which can be dumped when triggered by some event.

like a perf trace?

You ensure dev builds don't break stuff like that with realtime programming techniques. Dev tools exist and they're usually some combination of platform specific, expensive, buggy, and fragile.

printf and friends are fantastic when applicable. Sometimes the cost to even do an async print or even building in any mode except stripped release is impossible though, which usually leads to !fun!.

I mean that stopping execution will often break software logic, for example BLE connection will time out, SPI chip will stop communicate because of lack of commands, watchdog will reboot the chip, etc. And then the whole program will not work as expected, so debugging it will not make further sense. Sorry for miscommunication, I did not mean that hardware physically breaks. It might be possible to solve some of those issues, but generally printing is enough, at least that was my experience.

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