13.12 Pragma Restrictions and Pragma Profile
A
pragma
Restrictions expresses the user's intent to abide by certain restrictions.
A
pragma Profile
expresses the user's intent to abide by a set of Restrictions or other
specified run-time policies. These may facilitate the construction of
simpler run-time environments.
Syntax
The form of a
pragma
Restrictions is as follows:
Name Resolution Rules
Unless otherwise specified for
a particular restriction, the
expression
is expected to be of any integer type.
Legality Rules
Unless otherwise specified for a particular restriction,
the
expression
shall be static, and its value shall be nonnegative.
Paragraph 7 was deleted.
Post-Compilation Rules
A
pragma Restrictions
is a configuration pragma. If a
pragma
Restrictions applies to any compilation unit included in the partition,
this may impose either (or both) of two kinds of requirements, as specified
for the particular restriction:
A restriction may impose requirements on some or
all of the units comprising the partition. Unless otherwise specified
for a particular restriction, such a requirement applies to all of the
units comprising the partition and is enforced via a post-compilation
check.
A restriction may impose requirements on the run-time
behavior of the program, as indicated by the specification of run-time
behavior associated with a violation of the requirement.
For the purpose of
checking whether a partition contains constructs that violate any restriction
(unless specified otherwise for a particular restriction):
Generic instances are logically expanded at the
point of instantiation;
If an object of a type is declared or allocated
and not explicitly initialized, then all expressions appearing in the
definition for the type and any of its ancestors are presumed to be used;
A
default_expression
for a formal parameter or a generic formal object is considered to be
used if and only if the corresponding actual parameter is not provided
in a given call or instantiation.
Implementation Permissions
An implementation may provide implementation-defined
restrictions; the identifier for an implementation-defined restriction
shall differ from those of the language-defined restrictions.
An implementation may place limitations on the values
of the
expression
that are supported, and limitations on the supported combinations of
restrictions. The consequences of violating such limitations are implementation
defined.
An implementation is permitted to omit restriction
checks for code that is recognized at compile time to be unreachable
and for which no code is generated.
Whenever enforcement of a restriction is not required
prior to execution, an implementation may nevertheless enforce the restriction
prior to execution of a partition to which the restriction applies, provided
that every execution of the partition would violate the restriction.
Syntax
The form of a
pragma
Profile is as follows:
Legality Rules
Static Semantics
A profile is equivalent to the set of configuration
pragmas that is defined for each usage profile.
Post-Compilation Rules
A
pragma
Profile is a configuration pragma. There may be more than one
pragma
Profile for a partition.
Implementation Permissions
An implementation may provide implementation-defined
usage profiles; the identifier for an implementation-defined usage profile
shall differ from those of the language-defined usage profiles.
36 Restrictions intended to facilitate
the construction of efficient tasking run-time systems are defined in
D.7. Restrictions intended for use when constructing
high integrity systems are defined in
H.4.
37 An implementation has to enforce the
restrictions in cases where enforcement is required, even if it chooses
not to take advantage of the restrictions in terms of efficiency.
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