logging: Avoid compile error if debug prints are disabled

[jukkar]

If user has set this in .c file:

#define LOG_MODULE_NAME abc
#define LOG_LEVEL 0

#include <logging/log.h>
LOG_MODULE_REGISTER();

Here debug level is set to 0 which means that debug prints
are disabled. Then this compile error will be emitted:

include/logging/log_instance.h:83:47: error: ‘log_dynamic_abc’
undeclared (first use in this function);
did you mean ‘log_dynamic_xyz’?

The commit avoids this by setting debug macros to be no-op.

Signed-off-by: Jukka Rissanen [email protected]

[codecov-io]

Codecov Report

Merging #8828 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #8828      +/-   ##
==========================================
- Coverage   52.32%   52.32%   -0.01%     
==========================================
  Files         195      195              
  Lines       24730    24730              
  Branches     5140     5140              
==========================================
- Hits        12941    12940       -1     
  Misses       9715     9715              
- Partials     2074     2075       +1

Impacted Files	Coverage Δ
boards/posix/native_posix/timer_model.c	93.54% <0%> (-1.62%)	⬇️

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[nordic-krch]

I would like to avoid this solution because then macros are removed when logging is off. This tends to lead to some compilation warnings (e.g. when variables are created only for logging purpose). The initial goal was to keep logging macros pure C to avoid dead code.
I think that logger internals can be tweaked to handle that. I'll try to come up with the solution.

[jukkar]

Sure, that makes sense. This was just a quick solution in order to get things compiled.

[andrewboie]

Can we do this with empty inline functions instead?
That would alleviate problems with unused variables.

[jukkar]

Better solution in #8840 so no need to this PR.