Specifications

CAVR-4

Overriding default library modules

AVR® IAR C/C++ Compiler

Reference Guide

● Static variables are initialized except for __no_init and __eeprom declared

variables; this includes clearing zero-initialized memory and copying the ROM

image of the RAM memory of the remaining initialized variables

● The main function is called, which starts the application.

Note that the system startup code contains code for more steps than described here. The

other steps are applicable to the DLIB runtime environment.

SYSTEM TERMINATION

An application can terminate normally in two different ways:

● Return from the main function

● Call the exit function.

Because the ISO/ANSI C standard states that the two methods should be equivalent, the

cstartup code calls the exit function if main returns. The parameter passed to the

exit function is the return value of main. The default exit function is written in

assembler.

When the application is built in debug mode, C-SPY stops when it reaches the special

code label ?C_EXIT.

An application can also exit by calling the

abort function. The default function just

calls __exit in order to halt the system, without performing any type of cleanup.

Overriding default library modules

The IAR CLIB Library contains modules which you probably need to override with

your own customized modules, for example for character-based I/O, without rebuilding

the entire library. For information about how to override default library modules, see

Overriding library modules, page 61 in the chapter The DLIB runtime environment.

Customizing system initialization

For information about how to customize system initialization, see Customizing system

initialization, page 66.

Implementation of cstartup

For information about cstartup implementation, see Implementation of system startup

code, page 81 in the chapter The DLIB runtime environment.