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From: Bob Duff <bobduff@theworld.com>
Newsgroups: comp.lang.ada
Subject: Re: Arm - ravenscar - exceptions - last chance handler
Date: Sat, 30 May 2015 11:31:37 -0400
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Date: 2015-05-30T11:31:37-04:00
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jan.de.kruyf@gmail.com writes:

> How is last chance handler going to know the --length-- of the message?

It's a NUL-terminated string, as the comment in the spec says:

   procedure Raise_Exception (E : Exception_Id; Message : String := "");
   pragma No_Return (Raise_Exception);
   --  Unconditionally call __gnat_last_chance_handler. Message should be a
   --  null terminated string. Note that the exception is still raised even
   --  if E is the null exception id. This is a deliberate simplification for
   --  this profile (the use of Raise_Exception with a null id is very rare in
   --  any case, and this way we avoid introducing Raise_Exception_Always and
   --  we also avoid the if test in Raise_Exception).

> If we say that I have to append an ASCII.NUL when I raise an exception
> then it runs havoc with the other runtime modules where exceptions are
> used.

Why?  To raise an exception, you just say "raise Some_Exception;".
No need to fool about with ASCII.NUL, except in the last-chance
handler itself; the default version says:

         exit when Msg_Str (J) = Character'Val (0);

- Bob