HP C/iX Reference Manual (31506-90011)

Chapter 3 49

Data Types and Declarations

Initialization

storage duration are initialized at runtime when entering the block that contains the

deﬁnition of the object. An initialization of such an object is similar to an assignment

statement.

You can initialize a static object with a constant expression. You can initialize a static

pointer with the address of any previously declared object of the appropriate type plus or

minus a constant.

You can initialize an auto scalar object with an expression. The expression is evaluated at

run-time, and the resulting value is used to initialize the object.

When initializing a scalar type, you may optionally enclose the initializer in braces.

However, they are normally elided. For example,

int i = {3};

is normally speciﬁed as

inti=3;

When initializing the members of an aggregate, the initializer is a brace-enclosed list of

initializers. In the case of a structure with automatic storage duration, the initializer may

be a single expression returning a type compatible with the structure. If the aggregate

contains members that are aggregates, this rule applies recursively, with the following

exceptions:

• Inner braces may be optionally elided.

• Members that are themselves aggregates cannot be initialized with a single expression,

even if the aggregate has automatic storage duration.

In ANSI mode, the initializer lists are parsed "top-down;" in non-ANSI mode, they are

parsed "bottom-up." For example,

int q [3] [3] [2] = {

{1},

{2,3},

{4,5,6}

};

produces the following layout:

ANSI Mode Non-ANSI Mode

100000 102345

230000 600000

456000 000000

It is advisable to either fully specify the braces, or fully elide all but the outermost braces,

both for readability and ease of migration from non-ANSI mode to ANSI mode.

Because the compiler counts the number of speciﬁed initializers, you do not need to specify

the size in array declarations. The compiler counts the initializers and that becomes the

size:

int x[ ] = {1, 10, 30, 2, 45};

This declaration allocates an array of int called x with a size of ﬁve. The size is not

speciﬁed in the square brackets; instead, the compiler infers it by counting the initializers.