===================================================================
@@ -8964,7 +8964,60 @@
is
Has_Predefined_Or_Specified_Stream_Attribute : Boolean := False;
+ function Needs_Elementary_Stream_Operation
+ (T : Entity_Id) return Boolean;
+ -- AI05-0161 : if the restriction No_Default_Stream_Attributes is active
+ -- then we can generate stream subprograms for records that have scalar
+ -- subcomponents only if those subcomponents have user-defined stream
+ -- subprograms. For elementary types only 'Read and 'Write are needed.
+
+ ---------------------------------------
+ -- Needs_Elementary_Stream_Operation --
+ ---------------------------------------
+
+ function Needs_Elementary_Stream_Operation
+ (T : Entity_Id) return Boolean
+ is
+ begin
+ if not Restriction_Active (No_Default_Stream_Attributes) then
+ return False;
+
+ elsif Is_Elementary_Type (T) then
+ return No (TSS (T, TSS_Stream_Read))
+ or else No (TSS (T, TSS_Stream_Write));
+
+ elsif Is_Array_Type (T) then
+ return Needs_Elementary_Stream_Operation (Component_Type (T));
+
+ elsif Is_Record_Type (T) then
+ declare
+ Comp : Entity_Id;
+
+ begin
+ Comp := First_Component (T);
+ while Present (Comp) loop
+ if Needs_Elementary_Stream_Operation (Etype (Comp)) then
+ return True;
+ end if;
+ Next_Component (Comp);
+ end loop;
+ return False;
+ end;
+
+ elsif Is_Private_Type (T)
+ and then Present (Full_View (T))
+ then
+ return Needs_Elementary_Stream_Operation (Full_View (T));
+
+ else
+ return False;
+ end if;
+ end Needs_Elementary_Stream_Operation;
+
+ -- Start processing for Stream_Operation_OK
+
begin
+
-- Special case of a limited type extension: a default implementation
-- of the stream attributes Read or Write exists if that attribute
-- has been specified or is available for an ancestor type; a default
@@ -9057,6 +9110,7 @@
and then not Restriction_Active (No_Dispatch)
and then not No_Run_Time_Mode
and then RTE_Available (RE_Tag)
+ and then not Needs_Elementary_Stream_Operation (Typ)
and then RTE_Available (RE_Root_Stream_Type)
and then not Is_RTE (Typ, RE_Finalization_Collection);
end Stream_Operation_OK;
This new restriction is intended to prevent the use of the predefined stream attributes for elementary types. A consequence of this restriction is that the default implementation of stream attributes for composite types cannot be created if any of its elementary components lacks user-defined Read and Write attributes. Given the following configuration file: pragma Restrictions (No_Default_Stream_Attributes); Then the following must compile quietly: --- with Stdarg; procedure Main is begin null; end Main; --- and the following must execute quietly: with Ada.Streams.Stream_IO; use Ada.Streams.Stream_IO; procedure Stream_Test is -- Check that when restriction No_Default_Stream_Attributes is active, -- stream operations on composite types are usable if the type of their -- elementary components have user-defined stream operations. type Count is new Integer; procedure Dump_It (S : not null access Ada.Streams.Root_Stream_Type'Class; It : Count); for Count'Write use Dump_It; procedure Grab_It (S : not null access Ada.Streams.Root_Stream_Type'Class; It : out Count); for Count'Read use Grab_It; type Rec is record Value : Count; end record; procedure Dump_It (S : not null access Ada.Streams.Root_Stream_Type'Class; It : Count) is begin String'Output (S, Count'Image (It)); end; procedure Grab_It (S : not null access Ada.Streams.Root_Stream_Type'Class; It : out Count) is begin It := Count'Value (String'Input (S)); end Grab_It; Rec_File : File_Type; S : Stream_Access; Obj : Rec := (Value => -1234); Recovered : Rec; begin Create (Rec_File, Name => "temp"); S := Stream (Rec_File); Rec'Output (S, Obj); Close (Rec_File); Open (Rec_File, Name => "temp", Mode => In_File); Recovered := Rec'Input (S); if Obj /= Recovered then raise Program_Error; end if; end; --- After commenting out any of the attribute definitions above, compilation of stream_test.adb must yield: stream_test.adb:39:07: violation of restriction "No_Default_Stream_Attributes" at gnat.adc:1 Tested on x86_64-pc-linux-gnu, committed on trunk 2011-08-04 Ed Schonberg <schonberg@adacore.com> * exp_ch3.adb (Stream_Operation_Ok): new predicate Needs_Elementary_Stream_Operation, to determine whether user-defined Read and Write attributes are available for the elementary components of the given type. If only the predefined attributes are available, then when restriction No_Default_Stream_Attributes is active the predefined stream attributes for the composite type cannot be created.