Re: Handling signals in ADA

["David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>]

"Florian Weimer" <fw@deneb.enyo.de> wrote in message
news:87y9u6k7s6.fsf@deneb.enyo.de...
> Tomas Hlavaty <hlavaty@labe.felk.cvut.cz> writes:
>
> > Hi, could you help me with translating following C code to ADA?
>
> The programming language is called 'Ada'.
>
> > -- How to translate it to ADA?
>
> The standard Ada library does not support signals.  Typical Ada
> programs use other communication mechanisms, and a verbatim
> translation is not possible.  If you need signal handling because it's
> required by your environment, have a look at POSIX.5.

This answer is just plain wrong. The following program demonstrates
the use of signals in Ada, using only language-defined units.

Now. to be sure, because Ada restricts interrupt handlers to being
parameterless protected procedures, it is not possible to
pass parameter like what can be done under UNIX with the
standard C runtime, for example.

But the "standard Ada library" _DOES_ support signals.

-- begin source code

package body Signal_Handlers
is

   SIG_INT_Received : Boolean := False;

     function SIGINT_RECEIVED return BOOLEAN
     is
     begin
        return SIG_INT_Received;
     end SIGINT_Received;

   protected body Signals
   is
      procedure Handle_SIGINT
      is
      begin
         Ada.Text_IO.Put_Line ("SIGINT received..; Terminating.");
         SIG_INT_Received := True;
      end Handle_SIGINT;
      procedure Handle_SIGUSR1
      is
      begin
         Ada.Text_IO.Put_Line ("SIGUSR1 received and handled.");
      end Handle_SIGUSR1;
      procedure Handle_SIGUSR2
      is
      begin
         Ada.Text_IO.Put_Line ("SIGUSR2 received and handled.");
      end Handle_SIGUSR2;
   end Signals;

end Signal_Handlers;
with Ada.Interrupts.Names;
with Ada.Text_IO;
package Signal_Handlers
is
   pragma Unreserve_All_Interrupts;

   function SIGINT_Received return Boolean;
   protected Signals is
      procedure Handle_SIGINT;
      procedure Handle_SIGUSR1;
      procedure Handle_SIGUSR2;
   private
      pragma Attach_Handler
        (Handle_SIGINT, Ada.Interrupts.Names.SIGINT);
      pragma Attach_Handler
        (Handle_SIGUSR1, Ada.Interrupts.Names.SIGUSR1);
      pragma Attach_Handler
        (Handle_SIGUSR2, Ada.Interrupts.Names.SIGUSR2);
   end Signals;
end Signal_Handlers;
with Ada.Text_IO;
with Signal_Handlers;
procedure Test_Signal_Handler
is
begin
   loop
      exit when Signal_Handlers.SIGINT_Received;
      Ada.Text_IO.Put_Line ("I'm alive...");
      delay 1.0;
   end loop;
end Test_Signal_Handler;
.