INTERNATIONAL ISO/IEC STANDARD 23271 Third edition 2012-02-15 Information technology Common Language Infrastructure (CLl) Technologies de I'information - Infrastructure commune de langage (ICL) Reference number ISO/IEC 23271:2012(E) IEC @ISO/IEC2012 by IHS under lic itted without license from IHS Not for Resale ISO/IEC 23271:2012(E) COPYRIGHTPROTECTEDDOCUMENT @ISO/IEC2012 IsO's memberbody in the country of the requester. ISO copyright office Case postale 56 : CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland ISO/IEC 2012-All rights reserved etworking permitted without license from IHS Not for Resale ISO/IEC 23271:2012(E) Table of Contents Foreword xxi 1.1 Scope 1 1.2 Conformance 2 1.3 Normative references 3 1.4 Conventions 5 1.4.1 Organization 5 1.4.2 Informative text 5 1.5 Terms and definitions 6 1.6 Overview of the Common Language Infrastructure 9 1.6.1 Relationship to type safety 9 1.6.2 Relationship to managed metadata-driven execution 10 1.6.2.1 Managed code 10 1.6.2.2 Managed data 11 1.6.2.3 Summary 11 1.7 Common Language Specification 12 1.7.1 Introduction 12 1.7.2 Views of CLS compliance 12 1.7.2.1 CLS framework 12 1.7.2.2 CLS consumer 13 1.7.2.3 CLS extender 13 1.7.3 CLS compliance 14 1.7.3.1 Marking items as CLS-compliant 14 1.8 Common Type System 16 1.8.1 Relationship to object-oriented programming 19 1.8.2 Values and types 19 1.8.2.1 Value types and reference types 19 1.8.2.2 Built-in vaiue and reference types 20 1.8.2.3 Classes, interfaces, and objects 21 1.8.2.4 Boxing and unboxing of values 21 1.8.2.5 Identity and equality of values 22 1.8.3 Locations 23 1.8.3.1 Assignment-compatible locations 23 1.8.3.2 Coercion 23 1.8.3.3 Casting 24 @ISO/IEC 2012 2 - All rights reserved. ili pyrihenatialganizationfrSandadizatio etworking permitted without license from IHS Not for Resale ISO/IEC 23271:2012(E) 1.8.4 Type members 24 1.8.4.1 Fields, array elements, and values 24 1.8.4.2 Methods 24 1.8.4.3 Static fields and static methods 25 1.8.4.4 Virtual methods 25 1.8.5 Naming 25 1.8.5.1 Valid names 25 1.8.5.2 Assemblies and scoping 26 1.8.5.3 Visibility, accessibility, and security 27 1.8.6 Contracts 30 1.8.6.1 Signatures 30 1.8.7 Assignment compatibility 34 1.8.7.1 Assignment compatibility for signature types 37 1.8.7.2 Assignment compatibility for location types 38 1.8.7.3 General assignment compatibility 39 1.8.8 Type safety and verification 39 1.8.9 Type definers 39 1.8.9.1 Array types 40 1.8.9.2 Unmanaged pointer types 41 1.8.9.3 Delegates 41 1.8.9.4 Interface type definition 42 1.8.9.5 Class type definition 43 1.8.9.6 Object type definitions 44 1.8.9.7 Value type definition 47 1.8.9.8 Type inheritance 47 1.8.9.9 Object type inheritance 47 1.8.9.10 Value type inheritance 48 1.8.9.11 Interface type derivation 48 1.8.10 Member inheritance 48 1.8.10.1 Field inheritance 48 1.8.10.2 Method inheritance 48 1.8.10.3 Property and event inheritance 49 1.8.10.4 Hiding, overriding, and layout 49 1.8.11 Member definitions 50 1.8.11.1 Method definitions 50 1.8.11.2 Field definitions 51 1.8.11.3 Property definitions 51 1.8.11.4 Event definitions 52 1.8.11.5 Nested type definitions 52 iv @ ISO/IEC 2012 - All rights reserved. CopyrightIntenaionalOrganizationfor Standardization etworking permitted without license from IHS Not for Resale ISO/IEC 23271:2012(E) 1.9 Metadata 53 1.9.1 Components and assemblies 53 1.9.2 Accessing metadata 53 1.9.2.1 Metadata tokens 54 1.9.2.2 Member signatures in metadata 54 1.9.3 Unmanaged code 54 1.9.4 Method implementation metadata 54 1.9.5 Class layout 55 1.9.6 Assemblies: name scopes for types 55 1.9.7 Metadata extensibility 56 1.9.8 Globals, imports, and exports 57 1.9.9 Scoped statics 58 1.10 Name and type rules for the Common Language Specification 59 1.10.1 Identifiers 59 1.10.2 Overloading 59 1.10.3 Operator overloading 60 1.10.3.1 Unary operators 60 1.10.3.2 Binary operators 61 1.10.3.3 Conversion operators 62 1.10.4 Nam