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AVR IAR C/C++ CompilerReference Guide

for Atmel Corporations

AVRMicrocontroller

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COPYRIGHT NOTICE Copyright 19962005 IAR Systems. All rights reserved.

No part of this document may be reproduced without the prior written consent of IAR

Systems. The software described in this document is furnished under a license and may

only be used or copied in accordance with the terms of such a license.

DISCLAIMERThe information in this document is subject to change without notice and does not

represent a commitment on any part of IAR Systems. While the information containedherein is assumed to be accurate, IAR Systems assumes no responsibility for any errors

or omissions.

In no event shall IAR Systems, its employees, its contractors, or the authors of this

document be liable for special, direct, indirect, or consequential damage, losses, costs,

charges, claims, demands, claim for lost profits, fees, or expenses of any nature or kind.

TRADEMARKSIAR Systems, From Idea to Target, IAR Embedded Workbench, visualSTATE, IAR

MakeApp and C-SPY are trademarks owned by IAR Systems AB.

Atmel is a registered trademark of Atmel Corporation. AVR is a registered trademark of

Atmel Corporation.

Microsoft and Windows are registered trademarks of Microsoft Corporation.

All other product names are trademarks or registered trademarks of their respective

owners.

EDITION NOTICE

Fourth edition: February 2005

Part number: CAVR-4

This guide applies to version 4.x of AVR IAR Embedded Workbench.

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iii

Brief contentsTables ...................................................................................................................... xv

Preface ................................................................................................................... xix

Part 1. Using the compiler......................................................... 1

Getting started .................................................................................................... 3

Data storage ...................................................................................................... 15

Functions ............................................................................................................. 27

Placing code and data .................................................................................... 33

The DLIB runtime environment ............................................................... 53

The CLIB runtime environment .............................................................. 85

Assembler language interface ................................................................... 93

Using C++ .......................................................................................................... 109

Efficient coding for embedded applications ...................................... 121

Part 2. Compiler reference ....................................................135

Data representation ...................................................................................... 137

Segment reference ......................................................................................... 149

Compiler options ........................................................................................... 167

Extended keywords ....................................................................................... 203

Pragma directives ............................................................................................ 215

The preprocessor ........................................................................................... 227

Intrinsic functions ........................................................................................... 237

Library functions ............................................................................................. 243

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Implementation-defined behavior .......................................................... 255

IAR language extensions ............................................................................. 269

Diagnostics ......................................................................................................... 279

Index ..................................................................................................................... 281

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v

ContentsTables ...................................................................................................................... xv

Preface ................................................................................................................... xix

Who should read this guide ..............................................................xix

How to use this guide .........................................................................xixWhat this guide contains ..................................................................... xx

Other documentation..........................................................................xxi

Further reading ..................................................................................xxi

Document conventions ......................................................................xxii

Typographic conventions .................................................................xxii

Part 1. Using the compiler ......................................................... 1

Getting started .................................................................................................... 3

IAR language overview ...........................................................................3

Building applicationsan overview ..................................................4

Compiling ............................................................................................. 4

Linking ................................................................................................. 4

Basic settings for project configuration ..........................................5

Processor configuration ........................................................................ 5

Memory model .....................................................................................9

Size of double floating-point type ......................................................10

Optimization for speed and size .........................................................10

Runtime environment ......................................................................... 11

Special support for embedded systems ........................................ 12

Extended keywords ............................................................................ 12

Pragma directives ...............................................................................13

Predefined symbols ............................................................................13

Header files for I/O ............................................................................13

Accessing low-level features .............................................................13

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Data storage ...................................................................................................... 15

Introduction .............................................................................................. 15

Storing data ........................................................................................15

Extended keywords for data ...............................................................16

Memory models ......................................................................................17

Specifying a memory model ..............................................................17

Memory types and memory attributes ......................................... 18Using data memory attributes ............................................................19

Pointers and memory types ................................................................ 20

Structures and memory types ............................................................21

More examples ...................................................................................21

C++ and memory types ...................................................................... 22

The stack and auto variables ............................................................. 23

Dynamic memory on the heap ........................................................25

Functions ............................................................................................................. 27

Controlling functions ............................................................................27

Extended keywords for functions ......................................................27

Function storage .....................................................................................28

Special function types ..........................................................................29

Interrupt functions ...............................