HP C/iX Reference Manual (31506-90011)

34 Chapter3

Data Types and Declarations

Type Qualiﬁers

When a type qualiﬁer is used with a variable typed by a typedef name, the qualiﬁer is

applied without regard to the contents of the typedef. For example,

typedef int *t_ptr_to_int;

volatile t_ptr_to_int vol_ptr_to_int;

In the example above, the type of vol_ptr_to_int is volatile t_ptr_to_int, which

becomes volatile pointer to int. If the type t_ptr_to_int were substituted directly

in the declaration,

volatile int *ptr_to_vol_int;

the type would be pointer to volatile int.

Type qualiﬁers apply to objects, not to types. For example,

typedef int *t;

const t *volatile p;

In the example above, p is a volatile pointer to a const pointer to int. volatile applies to

the object p, while const applies to the object pointed to by p. The declaration of p can also

be written as follows:

t const *volatile p;

If an aggregate variable such as a structure is declared volatile, all members of the

aggregate are also volatile.

If a pointer to a volatile object is converted to a pointer to a non-volatile type, and the

object is referenced by the converted pointer, the behavior is undeﬁned.

int const *volatile vpci; Declares a volatile pointer to a constant int.

const *pci; Declares a pointer to a constant int. Since no

type speciﬁer was given, it defaults to int.

Table 3-2. Declarations using const and volatile

Declaration Meaning