DEVELHELP flag in Makefiles

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1

Hi everyone,

Can someone explain me what this flag in Makefile examples do ?

I just finished an app for a custom board. As my Makefile was based on an example, there was still this flag present. As its comment suggests, it's for development so I decided to remove it.

After removing it, my application starts normally right after flashing my board but as soon as I unplug it from power supply and plug it again, the app doesn't start anymore. I flashed the app on a Nucleo-F303RE to get some console output but I just get garbage from pyterm. I decided to keep this flag as it works flawlessly with it and takes only 4kB more in ROM but it could be great if someone knows a little more about it.

What could cause my app on two boards to fail starting without this flag ? In my app, I use some DEBUG() macros, I start two threads, do some UDP packets exchanges with another boards and that's it.

Best regards

Joel

2

Hi Joel,

It enables additional debug output and sanity checks. You can find more information at [1].

Kind regards, Bas

[1] https://riot-os.org/api/group__utils.html

3

Thank you for your answer. I've already read the docs but my real question was why do I get this "strange" behaviour ? My app works fine with the flag (flashed on over 50 boards) but without it the app can't start anymore as soon as I unplug the board from power and replug it. With the flag I have no issue.

Where can I look for something bad in my code that can explain this difference ? I looked a bit in the RIOT source code but didn't find anything for the moment that can give me an answer.

Envoyé par BlueMail<http://www.bluemail.me/r?b=14874>

4

In the docs, we find :

"Additional code parts such as (extensive) debug output and sanity checks using assertions. To activate it set environment variable DEVELHELP=1, or disable explicitly with DEVELHELP=0." https://riot-os.org/api/group__utils.html<https://riot-os.org/api/group__utils.htm>

But, everywhere in RIOT source code, the DEVELHELP is checked with "#ifdef DEVELHELP" or "#if defined(DEVELHELP)". So, correct me if I'm wrong, but it shouldn't change anything if the DEVELHELP is set to 0, 1 or anything else ? In this case, the doc is wrong ? We really need to comment it out as suggested in the Makefiles of examples to remove it. But then it causes my app to not restart after simulated power outage.

5

Finally, I found that if I remove the flag DEVELHELP but I add the flag SCHED_TEST_STACK, my app survives the simulated power outages. Then I tried to work without any of these flags in my Makefile and to remove some #ifdef. After a while, I found that removing the #ifdef in files :

  • core/thread.c around line “cb->stack_start = stack;”

  • core/include/thread.h around line : “char *stack_start;”

was solving my issue.

I’m launching two threads in my app. One with THREAD_CREATE_SLEEPING and one with 0 as flags.

I’m curious to know why this solves my issue and how it affects RIOT ? Does anyone knows ?

1 Like
6

Hi Joel,