__rt_entry is the starting
point for a program using the ARM C library. Control passes to
all scatter-loaded regions have been relocated to their execution addresses.
The default implementation of
Sets up the heap and stack.
Initializes the C library by calling
Shuts down the C library, by calling
__rt_entry must end with a call to
one of the following functions:
atexit()-registered functions and shuts down the library.
Shuts down the library but does not call
Exits directly to the execution environment. It does not shut down the library and does not call