H.2 Documentation of Implementation Decisions
The implementation shall document
the range of effects for each situation that the language rules identify
as either a bounded error or as having an unspecified effect. If the
implementation can constrain the effects of erroneous execution for a
given construct, then it shall document such constraints. [The documentation
might be provided either independently of any compilation unit or partition,
or as part of an annotated listing for a given unit or partition. See
, and 1.1.2
was deleted.Implementation defined:
Information regarding bounded errors
and erroneous execution.
The range of effects for each bounded
error and each unspecified effect. If the effects of a given erroneous
construct are constrained, the constraints shall be documented.
5 Among the situations to be documented
are the conventions chosen for parameter passing, the methods used for
the management of run-time storage, and the method used to evaluate numeric
expressions if this involves extended range or extra precision.
Discussion: Look up “unspecified”
and “erroneous execution” in the index for a list of the
The management of run-time storage is particularly
important. For safety applications, it is often necessary to show that
a program cannot raise Storage_Error, and for security applications that
information cannot leak via the run-time system. Users are likely to
prefer a simple storage model that can be easily validated.
The documentation could helpfully take into
account that users may well adopt a subset to avoid some forms of erroneous
execution, for instance, not using the abort statement, so that the effects
of a partly completed assignment_statement
do not have to be considered in the validation of a program (see 9.8
For this reason documentation linked to an actual compilation may be
most useful. Similarly, an implementation may be able to take into account
use of the Restrictions pragma.