type_declaration ::=
typedef data_type type_identifier variable_dimension ;
| typedef interface_instance_identifier . type_identifier type_identifer ;
| typedef [ enum | struct | union | class ] type_identifier ;
The user can define a new type using typedef.
typedef int Myint;
This can then be instantiated as:
Myint a, b;
A type can be used before it is defined, provided it is first identified as a type by an empty typedef:
typedef Mytype;Mytype M = 1;typedef int Mytype;
Note that this does not apply to enumeration values, which must be defined before they are used.
User-defined type identifiers have the same scoping rules as data identifiers, except that hierarchical reference to type identifiers shall not be allowed. References to type identifiers defined within an interface through ports are allowed provided they are locally re-defined before being used.
interface intf_i;
typedef int data_t;
endinterface
module sub(intf_i p)
typedef p.data_t my_data_t;
my_data_t data; // type of ’data’ will be int when connected to interface aboveendmodule
User-defined type names must be used for complex data types in casting (see Section 3.14, below), which only allows simple type names, and as type parameter values when unpacked array types are used. Sometimes a user-defined type needs to be declared before the contents of the type has been defined. This is of use with user-defined types derived from enum, struct, union, and class.
For examples :
typedef enum type_declaration_identifier;typedef struct type_declaration_identifier;typedef union type_declaration_identifier;typedef class type_declaration_identifier;typedef type_declaration_identifier;
Note that, while this is useful for coupled definitions of classes, it cannot be used for coupled definitions of structures, since structures are statically declared and there is no support for pointers to structures.
The last form shows that the type of the user-defined type does not have to be defined in the forward declaration.
A typedef inside a generate shall not define the actual type of a forward definition that exists outside the
scope of the forward definition.