Each architecture needs a crt0.S file.  The crt0.S assembly routine
typically corresponds to the following pseudo-C code.  In addition,
each architecture needs any support routines that gcc-generated code
expects to find in the system library -- Alpha, for example, needs
divide subroutines.

The "getenvtest" test program is a very good test for proper crt0.S
functionality.


extern __noreturn __libc_init(void *, void *);

__noreturn _start(void)
{
  void *elf_data   = get_elf_data_address(); /* Usually the stack address */
  void *atexit_ptr = get_atexit_ptr();       /* Usually in a register */ 

  /* Some architectures need this for debugging to work */
  setup_null_stack_frame_if_necessary();

  __libc_init(elf_data, atexit_ptr);
}