COSTELLO@amstel.llnl.gov (07/03/89)
> Reply to Shared Variables question . . .
--
-- Nicholas,
-- The variable 'Letter' in the Access_Variable task is never being updated.
-- It gets initialized to '*' (at elaboration time - before the Write_Letter_A_
-- To_Variable task starts to run), and remains '*'. Add the line of code
-- in Access_Variable to continually read from the global 'Unprotected'
-- variable. (Or replace 'PUT_LINE(Letter)' with 'PUT_LINE(Unprotected)')
--
-- Ed
--
with Text_IO; use Text_IO;
procedure Unprotected_Shared_Variable is
--
-- This is global to both tasks ...
--
Unprotected : Character := '*';
pragma SHARED(Unprotected);
task Write_Letter_A_To_Variable;
task Access_Variable;
task body Write_Letter_A_To_Variable is
--
-- 'Letter' is local to this task
--
Letter : constant Character := 'A';
begin
loop
--
-- And is stuck into the GLOBAL variable 'Unprotected'
--
-- This part is correct . . .
--
Unprotected := Letter;
delay 0.5;
end loop;
end Write_Letter_A_To_Variable;
task body Access_Variable is
--
-- 'Letter' is local to this task . . .
-- and is initialized at ELABORATION TIME.
-- (That is, it's only written one time, and
-- it gets written before the Write_Letter_A_To_Variable
-- task starts to run, so it will always be '*' ).
--
Letter : Character := Unprotected;
begin
loop
--
-- Insert this line and it will work fine . . .
--
Letter := Unprotected;
Put (Letter);
delay 3.0;
end loop;
end Access_Variable;
begin
null;
end Unprotected_Shared_Variable;
_________________________________________________________________________
-- Ed Costello
-- Lawrence Livermore National Lab
-- 1-415-422-1012