11.5 Suppressing Checks
instructions to an implementation on handling language-defined checks.
gives permission to an implementation to omit certain language-defined
checks, while a pragma
Unsuppress revokes the permission to omit checks..
(or simply, a “check”) is one
of the situations defined by this International Standard that requires
a check to be made at run time to determine whether some condition is
A check fails
when the condition being
checked is False, causing an exception to be raised.
The forms of checking
pragmas are as follows:
This paragraph was
A checking pragma applies to the named check in
a specific region, and applies to all entities in that region. A checking
pragma given in a declarative_part
or immediately within a package_specification
applies from the place of the pragma
to the end of the innermost enclosing declarative region. The region
for a checking pragma given as a configuration pragma is the declarative
region for the entire compilation unit (or units) to which it applies.
If a checking pragma applies to a generic_instantiation
then the checking pragma also applies to the entire instance.
Suppress gives permission to an implementation to omit the named check
(or every check in the case of All_Checks) for any entities to which
If permission has been given to suppress
a given check, the check is said to be suppressed
Unsuppress revokes the permission to omit the named check (or every check
in the case of All_Checks) given by any pragma
Suppress that applies at the point of the pragma
Unsuppress. The permission is revoked for the region to which the pragma
Unsuppress applies. If there is no such permission at the point of a
then the pragma
has no effect. A later pragma
Suppress can renew the permission.
The following are the
The following checks correspond
to situations in which the exception Constraint_Error is raised upon
When evaluating a dereference (explicit or implicit), check that the
value of the name
is not null
. When converting to a subtype that excludes null,
check that the converted value is not null
Check that the discriminants of a composite value have the values imposed
by a discriminant constraint. Also, when accessing a record component,
check that it exists for the current discriminant values.
Check that the second operand is not zero for the operations /, rem
Check that the bounds of an array value are equal to the corresponding
bounds of an index constraint. Also, when accessing a component of an
array object, check for each dimension that the given index value belongs
to the range defined by the bounds of the array object. Also, when accessing
a slice of an array object, check that the given discrete range is compatible
with the range defined by the bounds of the array object.
Check that two arrays have matching components, in the case of array
subtype conversions, and logical operators for arrays of boolean components.
Check that a scalar value is within the base range of its type, in cases
where the implementation chooses to raise an exception instead of returning
the correct mathematical result.
Check that a scalar value satisfies a range constraint. Also, for the
elaboration of a subtype_indication
check that the constraint
(if present) is compatible with the subtype denoted by the subtype_mark
Also, for an aggregate
check that an index or discriminant value belongs to the corresponding
subtype. Also, check that when the result of an operation yields an array,
the value of each component belongs to the component subtype.
Check that operand tags in a dispatching call are all equal. Check for
the correct tag on tagged type conversions, for an assignment_statement
and when returning a tagged limited object from a function.
The following checks correspond
to situations in which the exception Program_Error is raised upon failure.
Check the accessibility level of an entity or view.
For an allocator
check that the master of any tasks to be created by the allocator
is not yet completed or some dependents have not yet terminated, and
that the finalization of the collection has not started.
When a subprogram or protected entry is called, a task activation is
accomplished, or a generic instantiation is elaborated, check that the
body of the corresponding unit has already been elaborated.
This paragraph was deleted.
The following check
corresponds to situations in which the exception Storage_Error is raised
Check that evaluation of an allocator
does not require more space than is available for a storage pool. Check
that the space available for a task or subprogram has not been exceeded.
The following check
corresponds to all situations in which any predefined exception is raised.
Represents the union of all checks; suppressing All_Checks suppresses
all checks other than those associated with assertions. In addition,
an implementation is allowed (but not required) to behave as if a pragma
Assertion_Policy(Ignore) applies to any region to which pragma Suppress(All_Checks)
If a given check has been suppressed,
and the corresponding error situation occurs, the execution of the program
An implementation is allowed to place restrictions
on checking pragmas, subject only to the requirement that pragma
Unsuppress shall allow any check names supported by pragma
Suppress. An implementation is allowed to add additional check names,
with implementation-defined semantics.
has been suppressed, an implementation may also suppress an unspecified
subset of the Range_Checks.
An implementation may support an additional parameter
Unsuppress similar to the one allowed for pragma
Suppress (see J.10
). The meaning of such a
parameter is implementation-defined.
The implementation should minimize the code executed
for checks that have been suppressed.
is no guarantee that a suppressed check is actually removed; hence a
should be used only for efficiency reasons.
4 It is possible to give both a pragma
Suppress and Unsuppress for the same check immediately within the same
In that case, the last pragma
given determines whether or not the check is suppressed. Similarly, it
is possible to resuppress a check which has been unsuppressed by giving
in an inner declarative region.
Examples of suppressing
and unsuppressing checks:
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