From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	ip-172-31-65-14.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.6
Path: eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail
From: Doctor Who <doc@tardis.org>
Newsgroups: comp.lang.ada
Subject: Re: Discriminants or Constructor Function for Limited Types
Date: Mon, 09 May 2022 12:19:19 +0200
Organization: A noiseless patient Spider
Message-ID: <sjqh7hh9pv2gqalco1s50l390454mc3hf3@4ax.com>
References: <0b4ddd38-1f19-44fe-acd9-43a316ec9d29n@googlegroups.com> <t4ti4a$s1u$1@gioia.aioe.org> <t4v3f0$lgb$1@dont-email.me> <t4vsfi$jtb$1@gioia.aioe.org> <t51v2o$enb$1@dont-email.me> <t52nd4$vj2$1@gioia.aioe.org> <t54osn$hqf$1@dont-email.me> <t5619r$10bc$1@gioia.aioe.org> <t57a3o$e76$1@dont-email.me> <t57vgs$4su$1@gioia.aioe.org> <7puf7h59k2e2ns66918i95s847na2b8num@4ax.com> <t590fe$3ef$1@gioia.aioe.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Injection-Info: reader02.eternal-september.org; posting-host="5a30916ed513fc626fe39b717d553480";
	logging-data="22516"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+hWmRMKkohizD/ThXjVDYi"
User-Agent: ForteAgent/8.00.32.1272
Cancel-Lock: sha1:Iogn8RutB4uzU3i9mXVl5F57dSc=
Xref: reader02.eternal-september.org comp.lang.ada:63834
List-Id: <comp.lang.ada>

On Sun, 8 May 2022 20:00:15 +0200, "Dmitry A. Kazakov"
<mailbox@dmitry-kazakov.de> wrote:

>On 2022-05-08 19:19, Doctor Who wrote:
>> On Sun, 8 May 2022 10:37:48 +0200, "Dmitry A. Kazakov"
>
>>> Note, that your code is already unsafe because nobody knows if
>>> Create_or_Open_Output always opens the file and because there is no
>>> guarantee that the file is closed, while the design
>>>
>>>     declare
>>>        Output_File : Some_File_Type;
>>>     begin
>>>        Write_Output (Output_File, Data);
>>>     end;
>>>
>>> is 100% safe.
>> 
>> Not in the case that your data space is exhausted, in that case
>> Write_Output will fail, because you have no checks of free space
>> before writing.
>
>Upon a write error an exception will propagate and Output_File will go 
>out of the scope. The file will be closed and the exception will 
>continue its way. This is a safe behavior. Randy's code is unsafe and 
>requires catching and re-raising I/O exceptions in the client code.
>
>This is an illustration why exceptions should be allowed to propagate 
>out of Finalize. When Finalize is used to close a handle this may fail 
>and there is no way to retry inside Finalize. The choice in Ada is 
>between aborting the program or sweeping the problem under the rug 
>ignoring the problem. A more sane approach would be to propagate 
>exception out of Finalize indicating the problem.

if you do a check before write there is no need to rise and propagate
an exception.