E.2.3 Remote Call Interface Library Units
A remote call interface library unit can be used
as an interface for remote procedure calls (RPCs) (or remote function
calls) between active partitions.
Syntax
The
form of a
pragma
Remote_Call_Interface is as follows:
pragma Remote_Call_Interface[(
library_unit_name)];
The form of a
pragma
All_Calls_Remote is as follows:
pragma All_Calls_Remote[(
library_unit_name)];
A
pragma
All_Calls_Remote is a library unit pragma.
Legality Rules
A
pragma Remote_Call_Interface
is used to specify that a library unit is a
remote call interface
(RCI), namely that the Remote_Call_Interface aspect
of the library unit is True. A subprogram declared in the visible part
of such a library unit, or declared by such a library unit, is called
a
remote subprogram.
The declaration of an RCI library unit shall be preelaborable
(see
10.2.1), and shall depend semantically
only upon declared pure
library_items,
shared passive library units, remote types library units, other remote
call interface library units, or preelaborated normal library units that
are mentioned only in private with clauses.
In addition, the following
restrictions apply to an RCI library unit:
its visible part shall not contain the declaration
of a variable;
its visible part shall not contain the declaration
of a limited type;
it shall not be, nor shall its visible part contain,
the declaration of a subprogram for which aspect Inline is True;
it shall not be, nor shall its visible part contain,
a subprogram (or access-to-subprogram) declaration whose profile has
a parameter or result of a type that does not support external streaming
(see
13.13.2);
any public child of the library unit shall be a
remote call interface library unit.
A pragma All_Calls_Remote sets the All_Calls_Remote
representation aspect of
the
library unit to which the pragma applies to the value True. If the All_Calls_Remote
aspect of a library unit is True, the library unit shall be a remote
call interface.
Post-Compilation Rules
A remote call interface library unit shall be assigned
to at most one partition of a given program. A remote call interface
library unit whose parent is also an RCI library unit shall be assigned
only to the same partition as its parent.
Notwithstanding
the rule given in
10.2, a compilation unit
in a given partition that semantically depends on the declaration of
an RCI library unit,
needs (in the sense of
10.2)
only the declaration of the RCI library unit, not the body, to be included
in that same partition. Therefore, the body of an RCI library unit is
included only in the partition to which the RCI library unit is explicitly
assigned.
Implementation Requirements
If aspect All_Calls_Remote
is True for a given RCI library unit, then the implementation shall route
any of the following calls through the Partition Communication Subsystem
(PCS); see
E.5:
A direct call to a subprogram of the RCI unit from
outside the declarative region of the unit;
An indirect call through a remote access-to-subprogram
value that designates a subprogram of the RCI unit;
A dispatching call with a controlling operand designated
by a remote access-to-class-wide value whose tag identifies a type declared
in the RCI unit.
Implementation Permissions
An implementation need not support the Remote_Call_Interface
pragma or aspect nor the All_Calls_Remote pragma. Explicit message-based
communication between active partitions can be supported as an alternative
to RPC.
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