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6.3.2 Inline Expansion of Subprograms

[Subprograms may be expanded in line at the call site.] 


{program unit pragma (Inline) [partial]} {pragma, program unit (Inline) [partial]} The form of a pragma Inline, which is a program unit pragma (see 10.1.5), is as follows: 
  pragma Inline(name {, name});

Legality Rules

The pragma shall apply to one or more callable entities or generic subprograms.

Static Semantics

If a pragma Inline applies to a callable entity, this indicates that inline expansion is desired for all calls to that entity. If a pragma Inline applies to a generic subprogram, this indicates that inline expansion is desired for all calls to all instances of that generic subprogram.
Ramification: Note that inline expansion is desired no matter what name is used in the call. This allows one to request inlining for only one of several overloaded subprograms as follows: 
package IO is
   procedure Put(X : in Integer);
   procedure Put(X : in String);
   procedure Put(X : in Character);
   procedure Character_Put(X : in Character) renames Put;
   pragma Inline(Character_Put);
end IO;
with IO; use IO;
procedure Main is
   I : Integer;
   C : Character;
   Put(C); -- Inline expansion is desired.
   Put(I); -- Inline expansion is NOT desired.
end Main;
Ramification: The meaning of a subprogram can be changed by a pragma Inline only in the presence of failing checks (see 11.6).

Implementation Permissions

For each call, an implementation is free to follow or to ignore the recommendation expressed by the pragma.
Ramification: Note, in particular, that the recommendation cannot always be followed for a recursive call, and is often infeasible for entries. Note also that the implementation can inline calls even when no such desire was expressed by a pragma, so long as the semantics of the program remains unchanged. 
  {AI95-00309-01} An implementation may allow a pragma Inline that has an argument which is a direct_name denoting a subprogram_body of the same declarative_part.
Reason: This is allowed for Ada 83 compatibility. This is only a permission as this usage is considered obsolescent. 
Discussion: We only need to allow this in declarative_parts, because a body is only allowed in another body, and these all have declarative_parts.
6  The name in a pragma Inline can denote more than one entity in the case of overloading. Such a pragma applies to all of the denoted entities. 

Incompatibilities With Ada 83

{AI95-00309-01} {incompatibilities with Ada 83} A pragma Inline cannot refer to a subprogram_body outside of that body. The pragma can be given inside of the subprogram body. Ada 2005 adds an Implementation Permission to allow this usage for compatibility (and Ada 95 implementations also can use this permission), but implementations do not have to allow such pragmas.

Extensions to Ada 83

{extensions to Ada 83} A pragma Inline is allowed inside a subprogram_body if there is no corresponding subprogram_declaration. This is for uniformity with other program unit pragmas. 

Extensions to Ada 95

{AI95-00309-01} {extensions to Ada 95} Amendment Correction: Implementations are allowed to let Pragma Inline apply to a subprogram_body.

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