2.4.3. Bare machine C with floating‑point
If you want to use floating‑point processing in your application you must:
Perform the steps necessary for integer C as described in Bare machine integer C. However, do not build your application with the ‑‑fpu=none option.
Use the appropriate FPU option when you build your application.
Call _fp_init() to initialize the floating‑point status register before performing any floating‑point operations.
If you are using software floating‑point, you can also define the function __rt_fp_status_addr() to return the address of a writable data word to be used instead of the floating‑point status register. If you do not do this, the __user_libspace area is created, occupying 96 bytes. See The __user_libspace static data area for a description of the __user_libspace area.