Specifications

CAVR-4

Introduction

AVR® IAR C/C++ Compiler

Reference Guide

● On the heap. Once memory has been allocated on the heap, it remains valid until it

is explicitly released back to the system by the application. This type of memory is

useful when the number of objects is not known until the application executes. Note

that there are potential risks connected with using the heap in systems with a limited

amount of memory, or systems that are expected to run for a long time.

EXTENDED KEYWORDS FOR DATA

The extended keywords that can be used for data control the following:

● For data memory space, keywords that control the placement and type of objects

and pointers: __tiny, __near, __far, __huge, and __regvar

● For the EEPROM memory space, keyword that controls the placement and type of

objects and pointers:

__eeprom

● For the code (flash) memory space, keywords that control the placement and type of

objects and pointers: __tinyflash, __flash, __farflash, and __hugeflash

● For the I/O memory space, keyword that controls the placement and type of objects

and pointers: __ext_io, __io

● Special pointer that can access data objects in both data and code memory space:

__generic

● Other characteristics of objects: __root and __no_init.

See the chapter Data storage in Part 1. Using the compiler for more information about

how to use data memory types.

Syntax

The keywords follow the same syntax as the type qualifiers const and volatile. The

following declarations place the variable

i and j in EEPROM memory. The variables k

and l behave in the same way:

__eeprom int i, j;

int __eeprom k, l;

Note that the keyword affects both identifiers.

In addition to the rules presented here—to place the keyword directly in the code—the

directives

#pragma type_attribute and #pragma object_attribute can be used

for specifying the keywords. Refer to the chapter Pragma directives for details about

how to use the extended keywords together with pragma directives.

Pointers

A keyword that is followed by an asterisk (*), affects the type of the pointer being

declared. A pointer to EEPROM memory is thus declared by:

char __eeprom * p;