Apple Darwin User Manual download pdf (Page 2)

Contents

Introduction to 64-Bit Transition Guide 6

What Is 64-Bit Computing? 6

Who Should Read This Document? 6

Organization of This Document 6

See Also 7

Should You Recompile Your Software as a 64-Bit Executable? 8

Automatic Reference Counting 8

Operating System Version 8

I/O Kit Drivers and Other Kernel Extensions 9

Performance-Critical Applications 9

“Huge” Data Objects 10

64-Bit Math Performance 10

Plug-in Compatibility 10

Memory Requirements 11

Major 64-Bit Changes 12

Tools Changes 12

Data Type Changes 12

Data Type Size and Alignment 12

Data Type Impact on Code 14

Security Changes 15

Making Code 64-Bit Clean 16

General Programming Tips 16

Data Type and Alignment Tips 19

Avoiding Pointer-to-Integer Conversion 22

Working with Bits and Bitmasks 23

Tools Tips 24

Alignment Pragmas 24

Sign Extension Rules for C and C-derived Languages 25

Velocity Engine and SSE Alignment Tips 27

Porting Assembly Language Code 27

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Apple Darwin User Manual Page 2