6.9 System Initialization

Before you can run a C/C++ program, you must create the C/C++ run-time environment. The C/C++ boot routine performs this task using a function called _c_int00. The run-time-support source library, rts.src, contains the source to this routine in a module named boot.c (or boot.asm).

To begin running the system, the _c_int00 function can be called by reset hardware. You must link the _c_int00 function with the other object files. This occurs automatically when you use the --rom_model or --ram_model link option and include a standard run-time-support library as one of the linker input files.

When C/C++ programs are linked, the linker sets the entry point value in the executable output file to the symbol _c_int00.

The _c_int00 function performs the following tasks to initialize the environment:

1. Reserves space for the user mode run-time stack, and sets up the initial value of the stack pointer (SP)
2. It initializes global variables by copying the data from the initialization tables to the storage allocated for the variables in the .bss section. If you are initializing variables at load time (--ram_model option), a loader performs this step before the program runs (it is not performed by the boot routine). For more information, see Section 6.9.3.
3. Executes the global constructors found in the global constructors table. For more information, see Section 6.9.3.6.
4. Calls the main() function to run the C/C++ program

You can replace or modify the boot routine to meet your system requirements. However, the boot routine must perform the operations listed above to correctly initialize the C/C++ environment.