From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.9 required=5.0 tests=BAYES_00,FORGED_GMAIL_RCVD,
	FREEMAIL_FROM autolearn=no autolearn_force=no version=3.4.4
X-Received: by 2002:ac8:1a45:: with SMTP id q5mr17240797qtk.345.1568137975335;
        Tue, 10 Sep 2019 10:52:55 -0700 (PDT)
X-Received: by 2002:a9d:77d1:: with SMTP id w17mr6117910otl.5.1568137974923;
 Tue, 10 Sep 2019 10:52:54 -0700 (PDT)
Path: 
 eternal-september.org!reader01.eternal-september.org!feeder.eternal-september.org!weretis.net!feeder6.news.weretis.net!feeder.usenetexpress.com!feeder-in1.iad1.usenetexpress.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!o24no5683503qtl.0!news-out.google.com!q23ni115qtl.1!nntp.google.com!o24no5683497qtl.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Tue, 10 Sep 2019 10:52:54 -0700 (PDT)
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com;
 posting-host=192.160.103.146;
 posting-account=1tLBmgoAAAAfy5sC3GUezzrpVNronPA-
NNTP-Posting-Host: 192.160.103.146
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <fc3ac55b-d5c8-4255-9889-7f4b3fe428d0@googlegroups.com>
Subject: potential Ada feature - comments?
From: Matt Borchers <mattborchers@gmail.com>
Injection-Date: Tue, 10 Sep 2019 17:52:55 +0000
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Xref: reader01.eternal-september.org comp.lang.ada:57126
Date: 2019-09-10T10:52:54-07:00
List-Id: <comp.lang.ada>

I often find myself writing the same code fragment in exception handlers.  =
That is, I catch and handle the specific exceptions and the cleanup code fo=
r the subprogram is identical.  I know that I can (and do) write a cleanup =
routine to handle this, but even so, the call to the cleanup routine must s=
till be added to every exception case in the handler.

procedure SUBPROGRAM is
   procedure CLEANUP is
   begin
      --free resources
      ...
   end CLEANUP;
begin
   --acquire resources
   ...
exception
   when X =3D>
      --something for X
      cleanup;
   when Y =3D>
      --something for Y
      cleanup;
   when Z =3D>
      --something for Z
      cleanup;
   when others =3D>
      --general case
      cleanup;
end SUBPROGRAM;

I propose something like the following:

begin
   --acquire resources
   ...
exception
   when X =3D>
      --something specific for X
      ...
   when Y =3D>
      --something specific for Y
      ...
   when Z =3D>
      --something specific for Z
      ...
   when others =3D>
      --general case
      ...
finally
   --free resources
   ...
end SUBPROGRAM;

The code in the finally block would run immediately before the stack frame =
is removed for the SUBPROGRAM regardless of whether the exception is re-rai=
sed.  I would expect that the 'finally' block would only be allowed immedia=
tely after an 'exception' handler block.  The following would NOT be allowe=
d:

begin
...
finally  --syntax error: finally must follow exception handler
  cleanup;
end SUBPROGRAM;

What do you all think?
1) It eliminates redundant code.
2) It eliminates a nested and unnecessary cleanup routine.
3) It would make me feel better when writing exception handlers.

Matt