4.3.10.7 Packed Attribute

The packed attribute forces the object or structure member to have the smallest possible alignment, that is, no alignment padding storage will be allocated for the declaration. Used in combination with the aligned attribute, packed can be used to set an arbitrary alignment restriction greater or lesser than the default alignment for the type of the variable or structure member.

If the CCI is enabled (see 3.6.3.4 Ext Option) a more portable macro, __pack (note the different spelling), is available.