Compile modules selectively in release vs debug to optimize flash usage in nRF52840

[Johan]

Hi,

We use the nRF52840 and have now run out of space using debug mode compilation (using CMake from bash).

When we compile in release mode, we get 50% full flash, so that is great.

What we want to accomplish now, is to be able to select which modules are compiled in release mode, and which are in debug mode.

For example:

- zephyr modules -> release compilation

- nordic modules -> release compilation

- our application src folder - debug compilation as we need to debug it - or be able to select which folders in that src-folder to compile as debug vs release mode.

Any advice on how we do this?

Best,

Johan

Ps. I also posted this question to the Zephyr slack/discord general/+nordic forum, but since they don't know about Nordic modules, I only would get answers on Zephyr modules in there, I ask selectively in each forum ;-). Ds.

[Håkon Alseth]

Hi Johan,

  

For example:

- zephyr modules -> release compilation

- nordic modules -> release compilation

- our application src folder - debug compilation as we need to debug it - or be able to select which folders in that src-folder to compile as debug vs release mode.

The only thing that comes to mind is to force GCC to set a specific optimize level on your sources, via the #pragma directive:

https://gcc.gnu.org/onlinedocs/gcc/Function-Specific-Option-Pragmas.html

 

You can guard that pragma + push/pop lines with a if defined(some_symbol). Note that this is not a portable solution.

 

Kind regards,

Håkon

[Johan]

Ok thanks Håkon.

I got this from Zephyrs discord channel help on Nordic subjects.

"

yes, that is possible. You can place dedicated compile options on a Zephyr library (the app library is a Zephyr library). For example in you toplevel CMakeLists.txt file you may do:

find_package(Zephyr ...)
project(my_project)
 
zephyr_library_compile_options(-O0)
target_sources(app ...)

That will make that particular library compile with -O0 while the rest of Zephyr compiles with the optimization you have specified in prj.conf / Kconfig(edited)

"

zephyr/Kconfig.zephyr

https://github.com/zephyrproject-rtos/zephyr/blob/main/Kconfig.zephyr#L275-L309

Docs / Latest » choice: Optimization level

https://docs.zephyrproject.org/latest/reference/kconfig/choice_536.html

prj.conf

tejlmand —
When using in prj.conf, remember to put CONFIG_ first, like: CONFIG_SIZE_OPTIMIZATIONS=y

[Håkon Alseth]

Hi Johan,

 

Thanks for updating the case. I did not find this option when looking myself, very good to see that its possible to do this in a portable way!

 

Kind regards,

Håkon