Atmel CAVR-4 Manual De Usuario

CAVR-4

Overriding default library modules

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.

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.

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.

For information about how to customize system initialization, see Customizing system 
initialization, page 66.

For information about 

cstartup

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