Ada and signal handling

[Didier Kryn]

Le 07/10/2019 à 18:06, Kacvinsky, Tom a écrit :
> I am using GCC 8.3.0 with the Ada tool chain, but cannot seem to find a way of
> unsetting the signal handlers the Ada run time inserts.  I do not want Ada to
> handle signals for me as I am in a missed C/C++/Ada code base and would prefer
> to have the C signal handlers used.
>
> Any ideas?
>
> Thanks,
>
> Tom

     Hello Tom.

     I subscribed to this list (and gcc) primarily to get help from Gnat 
people but never received any reply. I'm sure they don't read this list 
and I don't know how to reach them.

     I've no authority to reply on this list. I've just been a user of 
Ada and managed sometimes to play with signals.

     Ada's API for signals is the package Ada.Interrupts (see 
/usr/lib/gcc/x86_64-linux-gnu/6/adainclude/a-interr.ads or the like 
depending on the arch and version of gcc). You will see that Ada 
provisions the possibility for the runtime to reserve some signals - ie 
prevent user's action on these.

     More details can be found in lower level packages like 
System.Interrupt_Management (s-intman.ads and s-intman.adb) in which you 
can see which signals are reserved by Gnat's runtime library.

     The usual system-raised signals are mapped as follows:

      case signo is
          when SIGFPE =>
             raise Constraint_Error;
          when SIGILL =>
             raise Program_Error;
          when SIGSEGV =>
             raise Storage_Error;
          when SIGBUS =>
             raise Storage_Error;
          when others =>
null;
       end case;

     Gnat reserves yet another signal to abort tasks.

     SIGINT is also reserved although there must be a way to avoid it, 
but I don't remember how.

     I've mixed a lot Ada and C to call the C library to invoke IOCTL's, 
perform memory mapping and manipulate pipes, but never with C++.

     Only two possible situations make sense in my opinion: either your 
application is in Ada and you want to interface it with some C++ 
library, or your application is in C++ and you want to interface it to 
an Ada library.

     Question: is your main program in Ada or in C++?

         Didier