Configuration pragmas may either appear at the start of a compilation unit, or they can appear in a configuration pragma file to apply to all compilations performed in a given compilation environment.
GNAT also provides the
gnatchop utility to provide an automatic
way to handle configuration pragmas following the semantics for
compilations (that is, files with multiple units), described in the RM.
See Operating gnatchop in Compilation Mode for details.
However, for most purposes, it will be more convenient to edit the
gnat.adc file that contains configuration pragmas directly,
as described in the following section.
In the case of
Restrictions pragmas appearing as configuration
pragmas in individual compilation units, the exact handling depends on
the type of restriction.
Restrictions that require partition-wide consistency (like
recognized wherever they appear
and can be freely inherited, e.g. from a `with'ed unit to the `with'ing
unit. This makes sense since the binder will in any case insist on seeing
consistent use, so any unit not conforming to any restrictions that are
anywhere in the partition will be rejected, and you might as well find
that out at compile time rather than at bind time.
For restrictions that do not require partition-wide consistency, e.g. SPARK or No_Implementation_Attributes, in general the restriction applies only to the unit in which the pragma appears, and not to any other units.
The exception is No_Elaboration_Code which always applies to the entire object file from a compilation, i.e. to the body, spec, and all subunits. This restriction can be specified in a configuration pragma file, or it can be on the body and/or the spec (in eithe case it applies to all the relevant units). It can appear on a subunit only if it has previously appeared in the body of spec.