A.8.9 Typedef
Declarations whose storage class specifier is typedef do not declare objects; instead they define identifiers that name types. These identifiers are called typedef names.
- typedef-name:
- identifier
A typedef declaration attributes a type to each name among its declarators in the usual way (see Par.A.8.6). Thereafter, each such typedef name is syntactically equivalent to a type specifier keyword for the associated type.
For example, after
- typedef long Blockno, *Blockptr; typedef struct { double r, theta; } Complex;
the constructions
- Blockno b; extern Blockptr bp; Complex z, *zp;
are legal declarations. The type of b is long, that of bp is pointer to long, and that of z is the specified structure; zp is a pointer to such a structure. typedef does not introduce new types, only synonyms for types that could be specified in another way. In the example, b has the same type as any long object. Typedef names may be redeclared in an inner scope, but a non-empty set of type specifiers must be given. For example, does not redeclare Blockno, but does.