H.7 Extensions to Global and Global'Class Aspects
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In addition to the entities specified in
6.1.2,
the Global aspect may be specified for a subtype (including a formal
subtype), formal package, formal subprogram, and formal object of an
anonymous access-to-subprogram type.
Syntax
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The following additional syntax is provided to override the mode of a
formal parameter to reflect indirect effects on variables reachable from
the formal parameter by one or more access-value dereferences:
Name Resolution Rules
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The
object_name
that is associated with an
overriding mode shall resolve to statically
denote a formal object, or a formal parameter of the associated entity.
Static Semantics
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The presence of the reserved word
overriding in a global mode
indicates that the specification is overriding the mode of a formal parameter
with another mode to reflect the overall effect of an invocation of the
callable entity on the state associated with the corresponding actual
parameter.
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[As described in
6.1.2, the following rules
are defined in terms of operations that are performed by or on behalf
of an entity.]
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The Global aspect for a subtype identifies the global variables that
can be referenced during default initialization, adjustment as part of
assignment, finalization of an object of the subtype, or conversion to
the subtype, including the evaluation of any assertion expressions that
apply. If not specified for the first subtype of a derived type, the
aspect defaults to that of the ancestor subtype; if not specified for
a nonderived composite first subtype the aspect defaults to that of the
enclosing library unit; if not specified for a nonderived elementary
first subtype (or scalar base subtype), the aspect defaults to
null
in the absence of a predicate (or when the predicate is statically True),
and to that of the enclosing library unit otherwise. If not specified
for a nonfirst subtype
S, the Global aspect defaults to that of
the subtype identified in the
subtype_indication
defining
S.
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The Global'Class aspect may be specified for the first subtype of a tagged
type
T, indicating an upper bound on the Global aspect of any
descendant of
T. If not specified, it defaults to Unspecified.
Legality Rules
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For a tagged subtype
T, each mode of its Global aspect shall identify
a subset of the variables identified either by the corresponding mode,
or by the
in out mode, of the Global'Class aspect of the first
subtype of any ancestor of
T.
Extensions to Ada 2012
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
