18.2.12 The “On Bootstrap” Routine

Some hardware configurations require special initialization once most of the C/C++ runtime environment has been initialized, while StatusBEV is still set and before the main() function has been called. For instance, special hardware initialization and/or initialization of the environment might be required by an RTOS. To achieve this, there is an On Bootstrap hook provided, so that you do not need to customize the entire startup code sequence.

An empty weak implementation of the On Bootstrap routine (_on_bootstrap) is provided with the start-up code. It is called by the runtime startup code after most of the C/C++ language context initialization has been performed.

If you do need to implement your own version of this routine, you can modify the following stub (note the leading underscore character in the function’s name).

void _on_bootstrap(void)
{
  // Add code to be executed just before main() here
}

This routine can be placed into any source file in your project and you do not need to adjust any compiler options to have it executed.

This routine can be written assuming that the runtime environment has been mostly established. The StatusBEV is cleared immediately after this routine returns. See 18.2 Runtime Start-Up Code for the order in which the environment is set up.