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Last update Fri Aug 26 2005
D
Language
Phobos
Comparisons

· Lexical
· Modules
· Declarations
· Types
· Properties
· Attributes
· Pragmas
· Expressions
· Statements
· Arrays
· Structs & Unions
· Classes
· Interfaces
· Enums
· Functions
· Operator Overloading
· Templates
· Mixins
· Contracts
· Conditional Compilation
· Handling errors
· Garbage Collection
· Memory Management
· Floating Point
· Inline Assembler
· Interfacing To C
· Portability Guide
· Embedding D in HTML
· Named Character Entities
· Application Binary Interface

Structs & Unions

	AggregateDeclaration:
		Tag { DeclDefs }
		Tag Identifier StructBody
		Tag Identifier ;

	Tag:
		struct
		union

	StructBody:
		{ }
		{ StructBodyDeclarations }

	StructBodyDeclarations:
		StructBodyDeclaration
		StructBodyDeclaration StructBodyDeclarations

	StructBodyDeclaration:
		Declaration
		Invariant
		UnitTest
		StructAllocator
		StructDeallocator
	
They work like they do in C, with the following exceptions:
  • no bit fields
  • alignment can be explicitly specified
  • no separate tag name space - tag names go into the current scope
  • declarations like:
    	struct ABC x;
    	
    are not allowed, replace with:
    	ABC x;
    	
  • anonymous structs/unions are allowed as members of other structs/unions
  • Default initializers for members can be supplied.
  • Member functions and static members are allowed.
Structs and unions are meant as simple aggregations of data, or as a way to paint a data structure over hardware or an external type. External types can be defined by the operating system API, or by a file format. Object oriented features are provided with the class data type.

Static Initialization of Structs

Static struct members are by default initialized to whatever the default initializer for the member is, and if none supplied, to the default initializer for the member's type. If a static initializer is supplied, the members are initialized by the member name, colon, expression syntax. The members may be initialized in any order. Members not specified in the initializer list are default initialized.
	struct X { int a; int b; int c; int d = 7;}
	static X x = { a:1, b:2};	// c is set to 0, d to 7
	static X z = { c:4, b:5, a:2 , d:5};	  // z.a = 2, z.b = 5, z.c = 4, z.d = 5
	
C-style initialization, based on the order of the members in the struct declaration, is also supported:
	static X q = { 1, 2 };	  // q.a = 1, q.b = 2, q.c = 0, q.d = 7
	

Static Initialization of Unions

Unions are initialized explicitly.
	union U { int a; double b; }
	static U u = { b : 5.0 };		// u.b = 5.0
	
Other members of the union that overlay the initializer, but occupy more storage, have the extra storage initialized to zero.

Struct Properties

	.sizeof			Size in bytes of struct
	.alignof		Size boundary struct needs to be aligned on

Struct Field Properties

	.offsetof		Offset in bytes of field from beginning
				of struct

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