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,

   extern Blockno; does not redeclare Blockno, but

   extern int Blockno; does.