RE: How to add compiler options in nRF Connect SDK / implicit conversion from 'float' to 'double'

puz_md — Thu, 20 Feb 2025 11:18:15 GMT

Oh... this means that our v2.5.3 based implementation runs inefficiently, even without the warnings. Good to know.

Thanks for the feedback!

RE: How to add compiler options in nRF Connect SDK / implicit conversion from 'float' to 'double'

Håkon Alseth — Wed, 18 Dec 2024 10:08:50 GMT

Hi,

With Zephyr v3.6.0 and newer, this was added as a default warning flag:

https://docs.zephyrproject.org/latest/releases/release-notes-3.6.html

Added -Wdouble-promotion as a default warning when compiling to warn developers with single-precision floats easily being promoted to double-precision.

A typical function that emits such a warning is printf (and variants):

https://stackoverflow.com/questions/28097564/why-does-printf-promote-a-float-to-a-double

[quote user=""]

Later, I found another instruction that worked:
target_compile_options(app PRIVATE -fsingle-precision-constant)

[/quote]

You can also append using CONFIG_COMPILER_OPT="-f..."

[quote user=""]Question 2: What is the difference between add_compile_options() and target_compile_options()? Why did the first instruction not work?[/quote]

To my understanding, add_compile_options() works on a directory level, and not a target level. Ordering comes into play, and thus using a command to set it to the target is often recommended.

Kind regards,

Håkon