CMSIS-DSP rfft init throwing an error

[NicRoberts]

STM32WB55

arm_rfft_fast_instance_f32 fft_instance;
arm_rfft_fast_init_f32(&fft_instance, NUM_SAMP);

I'm trying to use the rfft_fast function from the arm_math.h library

But when I compile I get...

../STM32_WPAN/App/custom_app.c:122:24: error: expected declaration specifiers or '...' before '&' token

122 | arm_rfft_fast_init_f32(&fft_instance, NUM_SAMP);

| ^

../STM32_WPAN/App/custom_app.c:69:25: error: expected declaration specifiers or '...' before numeric constant

69 | #define NUM_SAMP 256

I looked at the docs & many examples of the init function, the usage is always as above. Compiles fine if I comment out the init function but obviously that is of no use to me.

[TDK · Accepted solution]

You can't call functions directly like this at the global scope. This needs to be within a function such as main().

If that's not it, include the full custom_app.c file that throws this error.

[NicRoberts]

Thanks, getting lost in my own code here...