Ada Reference Manual (Ada 2022)
J.9 The Storage_Size Attribute
Static Semantics
For any task subtype T, the following attribute is defined:
T'Storage_Size
Denotes an implementation-defined value of type universal_integer representing the number of storage elements reserved for a task of the subtype T.
Storage_Size may be specified for a task first subtype that is not an interface via an attribute_definition_clause. When the attribute is specified, the Storage_Size aspect is specified to be the value of the given expression.