4.11 Supported Attributes

The following attributes, invoked by __attribute__ ((keyword)), or alternatively by [[keyword]], are implemented by the compiler for compatibility:

always_inline — equivalent to #pragma inline and -xinline

noinline — equivalent to #pragma no_inline and -xinline

pure — equivalent to #pragma does_not_write_global_data

const — equivalent to #pragma no_side_effect

malloc — equivalent to #pragma returns_new_memory

constructor — equivalent to #pragma init

destructor — equivalent to #pragma fini

weak — equivalent to #pragma weak

noreturn — equivalent to #pragma does_not_return

visibility

returns_twice

packed — see below

atomic

outer

relaxed

mode

aligned

strong

4.11.1 `packed`

This attribute, attached to struct or union type definition, specifies that each member (other than zero-width bitfields) of the structure or union is placed to minimize the memory required. When attached to an enum definition, it indicates that the smallest integral type should be used.

Specifying this attribute for struct and union types is equivalent to specifying the packed attribute on each of the structure or union members.

In the following example struct my_packed_struct's members are packed closely together, but the internal layout of its s member is not packed. To do that, struct my_unpacked_struct would also need to be packed.

struct my_unpacked_struct
{
   char c;
   int i;
;
              
struct __attribute__ ((__packed__)) my_packed_struct
{
   char c;
   int  i;
   struct my_unpacked_struct s;
};

You may only specify this attribute on the definition of an enum, struct, or union, and not on a typedef that does not also define the enumerated type, structure, or union.

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	Oracle Solaris Studio 12.2: C++ User's Guide

4.11 Supported Attributes

4.11.1 __packed__

4.11.1 `packed`