Atmel CAVR-4 ユーザーズマニュアル

CAVR-4

Writing efficient code

Reference Guide

Normally, the runtime environment will initialize all global and static variables when the 
application is started.

The compiler supports the declaration of variables that will not be initialized, using the 

_ _no_init

 type modifier. They can be specified either as a keyword or using the 

#pragma

 

object_attribute

 directive. The compiler places such variables in 

separate segments, according to the specified memory keyword. See the chapter Placing 
code and data for more information.

For 

_ _no_init

, the 

const

 keyword implies that an object is read-only, rather than that 

the object is stored in read-only memory. It is not possible to give a 

_ _no_init

 object 

an initial value. 

Variables declared using the 

_ _no_init

 keyword could, for example, be large input 

buffers or mapped to special RAM that keeps its content even when the application is 
turned off.

For information about the 

_ _no_init

 keyword, see page 211. Note that to use this 

keyword, language extensions must be enabled; see -e, page 179. For information about 
the 

#pragma

 

object_attribute