C Language Reference Manual 007–0701–150 COPYRIGHT Copyright © 1999, 2002–2003 Silicon Graphics, Inc. All rights reserved; provided portions may be copyright in third parties, as indicated elsewhere herein. No permission is granted to copy, distribute, or create derivative works from the contents of this electronic documentation in any manner, in whole or in part, without the prior written permission of Silicon Graphics, Inc. LIMITED RIGHTS LEGEND The electronic (software) version of this document was developed at private expense; if acquired under an agreement with the USA government or any contractor thereto, it is acquired as "commercial computer software" subject to the provisions of its applicable license agreement, as specified in (a) 48 CFR 12.212 of the FAR; or, if acquired for Department of Defense units, (b) 48 CFR 227-7202 of the DoD FAR Supplement; or sections succeeding thereto. Contractor/manufacturer is Silicon Graphics, Inc., 1600 Amphitheatre Pkwy 2E, Mountain View, CA 94043-1351. TRADEMARKS AND ATTRIBUTIONS Silicon Graphics, SGI, the SGI logo, and IRIX are registered trademarks of Silicon Graphics, Inc. in the United States and/or other countries worldwide. Gaussian is a trademark of Gaussian, Inc. MIPSpro is a trademark of MIPS Technologies, Inc., and is used under license to Silicon Graphics, Inc. UNIX and the X device are trademarks of The Open Group in the United States and other countries. Cover Design By Sarah Bolles, Sarah Bolles Design, and Dany Galgani, SGI Technical Publications. New Features in This Manual Information regarding the use of lint-style comments in macros has been added to Appendix B, "lint-style Comments", page 167. 007–0701–150 iii Record of Revision Version Description 7.3 April 1999 This document has been updated to support the MIPSpro 7.3 release. 140 September 2002 This document has been updated to support the MIPSpro 7.4 release which runs on IRIX operating systems version 6.5 and later. 150 June 2003 This document has been updated to support the MIPSpro 7.4.1m release which runs on IRIX operating systems version 6.5 and later. 007–0701–150 v Contents About This Manual . ................. xix Related Publications . ................... xix Obtaining Publications . ................... xx Conventions . ........................ xxi Reader Comments ....................... xxi 1. An Overview of ANSI C . ................. 1 ANSI C . ........................ 1 Strictly Conforming Programs ................... 1 Name Spaces ........................ 1 Compiling ANSI Programs ................... 2 Guidelines for Using ANSI C ................... 2 Compiling Traditional C Programs . .............. 3 Helpful Programming Hints . ................... 3 Recommended Practices . ................... 3 Practices to Avoid . ................... 4 2. C Language Changes . ................. 7 Preprocessor Changes . ................... 7 Replacement of Macro Arguments in Strings .............. 8 Token Concatenation . ................... 9 Changes in Disambiguating Identifiers ................ 10 Scoping Differences . ................... 10 Name Space Changes . ................... 12 Changes in the Linkage of Identifiers................ 12 007–0701–150 vii Contents Types and Type Compatibility ................... 14 Type Promotion in Arithmetic Expressions . .............. 14 Type Promotion and Floating Point Constants .............. 15 Compatible Types . ................... 17 Argument Type Promotions ................... 17 Mixed Use of Functions . ................... 18 Function Prototypes . ................... 18 External Name Changes . ................... 20 Changes in Function Names ................... 20 Changes in Linker-Defined Names . .............. 20 Data Area Name Changes . ................... 21 Standard Headers ....................... 22 3. Lexical Conventions . ................. 23 Comments . ........................ 23 Identifiers.......................... 23 Keywords . ........................ 23 Constants . ........................ 24 Integer Constants . ................... 24 Character Constants . ................... 25 Special Characters . ................... 25 Trigraph Sequences (ANSI C Only) . .............. 26 Floating Constants . ................... 27 Enumeration Constants . ................... 28 String Literals ........................ 28 Operators . ........................ 28 Punctuators . ........................ 29 4. Meaning of Identifiers . ................. 31 viii 007–0701–150 C Language Reference Manual Disambiguating Names . ................... 31 Scope . ........................ 31 Block Scope ....................... 32 Function Scope . ................... 32 Function Prototype Scope ................... 32 File Scope ........................ 32 Name Spaces ........................ 33 Name Space Discrepancies Between Traditional and ANSI C ........ 33 Linkage of Identifiers..................... 34 Linkage Discrepancies Between Traditional and ANSI C . ......... 36 Storage Duration ....................... 37 Object Types . ........................ 38 Character Types ....................... 38 Integer and Floating Point Types .................. 38 Derived Types ....................... 40 void Type ........................ 40 Objects and lvalues ....................... 41 5. Operator Conversions . ................. 43 Conversions of Characters and Integers . .............. 43 Conversions of Float and Double .................. 43 Conversion of Floating and Integral Types . .............. 44 Conversion of Pointers and Integers . .............. 44 Conversion of unsigned Integers .................. 44 Arithmetic Conversions . ................... 45 Integral Promotions . ................... 45 Usual Arithmetic Conversions .................. 45 007–0701–150 ix Contents Traditional C Conversion Rules . .............. 46 ANSI C Conversion Rules ................... 46 Conversion of Other Operands ................... 47 Conversion of lvalues and Function Designators ............. 47 Conversion of void Objects ................... 47 Conversion of Pointers . ................... 48 6. Expressions and Operators ................. 49 Precedence and Associativity Rules in C . .............. 49 Primary Expressions . ................... 51 Postfix Expressions ....................... 51 Subscripts . ........................ 52 Function Calls ....................... 52 Structure and Union References .................. 54 Indirect Structure and Union References . .............. 54 postfix ++ and postfix - - .................. 54 Unary Operators ....................... 55 Address-of and Indirection Operators . .............. 55 Unary + and - Operators . ................... 56 Unary ! and ~ Operators . ................... 56 Prefix ++ and --Operators ................... 56 sizeof Unary Operator . ................... 57 Cast Operators ........................ 57 Multiplicative Operators . ................... 58 Additive Operators ....................... 59 Shift Operators ........................ 60 Relational Operators . ................... 60 Equality Operators ....................... 61 x 007–0701–150 C Language Reference Manual Bitwise AND Operator . ................... 62 Bitwise Exclusive OR Operator ................... 62 Bitwise Inclusive OR Operator ................... 63 Logical AND Operator . ................... 63 Logical OR Operator . ................... 63 Conditional Operator . ................... 64 Assignment Operators . ................... 65 Assignment Using = (Simple Assignment) . .............. 65 Compound Assignment . ................... 66 Comma Operator ....................... 66 Constant Expressions . ................... 66 Integer and Floating Point Exceptions . .............. 67 7. Declarations . ..................... 69 Storage Class Specifiers..................... 70 Type Specifiers........................ 71 Structure and Union Declarations .................. 72 Bitfields . ........................ 75 Enumeration Declarations . ................... 76 Type Qualifiers........................ 77 Declarators . ........................ 78 Meaning of Declarators . ................... 78 Pointer Declarators . ................... 79 Qualifiers and Pointers . ................... 79 Pointer-related Command Options . .............. 80 Array Declarators . ................... 81 Function Declarators and Prototypes . .............. 82 Prototyped Functions Summarized . .............. 84 007–0701–150 xi Contents Restrictions on Declarators . ................... 85 Type Names . ........................ 86 Implicit Declarations . ................... 87 typedef .......................... 87 Initialization . ........................ 88 Initialization of Aggregates ................... 89 Examples of Initialization . ................... 90 8. Statements . ..................... 93 Expression Statement . ................... 93 Compound Statement or Block ................... 93 Selection Statements . ................... 94 if Statement ........................ 94 switch Statement . ................... 95 Iteration Statements . ................... 95 while Statement . ................... 96 do Statement ........................ 96 for Statement ....................... 96 Jump Statements ....................... 97 goto Statement ....................... 97 continue Statement . ................... 97 break Statement . ................... 98 return Statement . ................... 98 Labeled Statements ....................... 98 9. External Definitions . ................. 101 External Function Definitions