These requirements are:

• Re-implement __rt_raise() if you are using the heap.
• Not define main(), to avoid linking in the library initialization code.

• Write an assembly language veneer that establishes the register state required to run C. This veneer must branch to the entry function in your application. The register state required to run C primarily comprises the stack pointer.

  The register state also consists of sb, the static base register, if Read/Write Position-Independent (RWPI) code applies.

• Provide your own RW/ZI initialization code.
• Ensure that your initialization veneer is executed by, for example, placing it in your reset handler.
• 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.