Specifying Attributes of Variables

The keyword __attribute__ allows you to specify special attributes of variables or structure fields. This keyword is followed by an attribute specification inside double parentheses. The following attributes are currently defined for variables:

• aligned
• mode
• nocommon
• packed
• section
• transparent_union
• cleanup
• unused
• deprecated

Other attributes are available for functions (see Function Attributes) and for types (see Type Attributes).

You may also specify attributes with __ preceding and following each keyword. This allows you to use them in header files without being concerned about a possible macro of the same name. For example, you may use __aligned__ instead of aligned.

See Attribute Syntax for details of the exact syntax for using attributes.

To specify multiple attributes, separate them by commas within the double parentheses: for example, __attribute__ ((aligned (16), packed)).