Fortran 2003 extends the data entities allowed for the ALLOCATABLE attribute. Previously this attribute was limited to locally stored array variables. It is now allowed with:
array components of structures
dummy arrays
array function results
polymorphic entities in a CLASS type specifier
Allocatable entities remain forbidden in all places where they may be storage-associated: COMMON blocks and EQUIVALENCE statements. Allocatable array components may appear in SEQUENCE types, but objects of such types are then prohibited from COMMON and EQUIVALENCE.