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C.4 Preelaboration Requirements
1
This clause specifies additional implementation
and documentation requirements for the Preelaborate pragma (see
10.2.1).
Implementation Requirements
2
The implementation shall not incur any run-time
overhead for the elaboration checks of subprograms and protected_bodies
declared in preelaborated library units.
3
The implementation shall not execute any memory
write operations after load time for the elaboration of constant objects
declared immediately within the declarative region of a preelaborated
library package, so long as the subtype and initial expression (or default
initial expressions if initialized by default) of the
object_declaration
satisfy the following restrictions.
The meaning of
load time is implementation defined.
4
- Any subtype_mark
denotes a statically constrained subtype, with statically constrained
subcomponents, if any;
5
- any constraint
is a static constraint;
6
- any allocator
is for an access-to-constant type;
7
- any uses of predefined operators appear
only within static expressions;
8
- any primaries
that are names, other than attribute_references
for the Access or Address attributes, appear only within static expressions;
9
- any name
that is not part of a static expression is an expanded name or direct_name
that statically denotes some entity;
10
- any discrete_choice
of an array_aggregate is static;
11
- no language-defined check associated
with the elaboration of the object_declaration
can fail.
Documentation Requirements
12
The implementation shall document any circumstances
under which the elaboration of a preelaborated package causes code to
be executed at run time.
13
The implementation shall document whether the
method used for initialization of preelaborated variables allows a partition
to be restarted without reloading.
Implementation Advice
14
It is recommended that preelaborated packages
be implemented in such a way that there should be little or no code executed
at run time for the elaboration of entities not already covered by the
Implementation Requirements.
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