Ada defines (throughout the Ada 2012 reference manual, summarized in Annex K) a set of aspects that can be specified for certain entities. These language defined aspects are implemented in GNAT in Ada 2012 mode and work as described in the Ada 2012 Reference Manual.
In addition, Ada 2012 allows implementations to define additional aspects whose meaning is defined by the implementation. GNAT provides a number of these implementation-defined aspects which can be used to extend and enhance the functionality of the compiler. This section of the GNAT reference manual describes these additional aspects.
Note that any program using these aspects may not be portable to other compilers (although GNAT implements this set of aspects on all platforms). Therefore if portability to other compilers is an important consideration, you should minimize the use of these aspects.
Note that for many of these aspects, the effect is essentially similar to the use of a pragma or attribute specification with the same name applied to the entity. For example, if we write:
type R is range 1 .. 100
with Value_Size => 10;
then the effect is the same as:
type R is range 1 .. 100;
for R'Value_Size use 10;
and if we write:
type R is new Integer
with Shared => True;
then the effect is the same as:
type R is new Integer;
pragma Shared (R);
In the documentation below, such cases are simply marked as being boolean aspects equivalent to the corresponding pragma or attribute definition clause.