Configure math.h lib with cmake on SDK Mesh

[Corentin]

Hello community!

I use the dongle PCA10059 (nrf52840) for my hardware. I already enable -DARM_MATH_CM4 and link library libarm_cortexM4lf_math.a with CMake. I can include arm_math.h in my project and use arm_power_f32 for example. But I also need to use sqrt function so I try to call arm_sqrt_f32 but I have an error return. "arm_math.h:5633: undefined reference to `sqrtf'"

I understand that compiler doesn't find math.h library. I'm not an expert of CMake so how I can enable math.h in the SDK Mesh? My project is in the example folder. I already try to add 

-lm but same issue. Can you guide me ? 

Thank you,

[Joakim Jakobsen]

Hi.

Maybe you could take a look at the suggestion in this thread:

https://devzone.nordicsemi.com/f/nordic-q-a/27715/nrf52832-how-to-include-the-arm_math-h-library

Best regards,
Joakim

[awneil]

Corentin said:

I understand that compiler doesn't find math.h library.

math.h isn't a library - it's just a header file.

It'll be the Linker that needs the library ...

[Corentin]

I already do this: add libarm_cortexM4l_math.a in include path and add define ARM_MATH_CM4. I can use functions in arm_math.h execpt function pointed to "math.h"

[awneil]

Corentin said:

add libarm_cortexM4l_math.a in include path

Now that one is a Library, so you need to add it to the Linker's libraries path - not the compiler's include path.

[Corentin]

set(MATH_LINK_LIBRARIE ${MATH_LINK_LIBRARIE} ${CMAKE_SOURCE_DIR}/firmware/lib/nRF5_SDK_15.2.0_9412b96/components/toolchain/cmsis/dsp/GCC/libarm_cortexM4lf_math.a)

target_link_libraries(${target_debug}
    rtt_${PLATFORM}
    uECC_${PLATFORM}
    ${MATH_LINK_LIBRARIE})

Yes sorry i link the library like this (already do with RTT and uECC).